研究者詳細 - 堀田　篤

論文 - 堀田　篤

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Thermally Reversible Gel-Sol Transition of Hydrogels via Dissociation and Association of an Artificial Protein Nanocage

Nasu E., Kawakami N., Takamura S., Hotta A., Arai R., Miyamoto K.

Biomacromolecules （Biomacromolecules） 25 （ 4 ） 2358 - 2366 2024年04月

ISSN 15257797

Oligomeric protein nanocages often disassemble into their subunits and reassemble by external stimuli. Thus, using these nanocages as cross-linkers for hydrogel network structures is a promising approach to allow hydrogels to undergo stimuli-responsive gel-sol transitions or self-healing. Here, we report hydrogels that show a reversible gel-sol transition resulting from the heat-induced dissociation and reassociation of protein nanocages. The hydrogel contained the 60-mer artificial protein nanocage, TIP60, as a supramolecular cross-linker for polyethylene glycol network structures. The hydrogel showed a gel-to-sol transition upon heating at a temperature above the melting point of TIP60 and immediately returned to a gel state upon cooling to room temperature. During the heating and cooling treatment of the hydrogel, small-angle X-ray scattering analysis suggested the dissociation and reassociation of TIP60. Furthermore, we demonstrated redox-responsive cargo release from TIP60 in the hydrogel. These results showed the potential of TIP60 as a component of multi-stimuli-responsive hydrogels.

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Contact-Killing Antibacterial Polystyrene Polymerized Using a Quaternized Cationic Initiator

Jitsuhiro A., Maeda T., Ogawa A., Yamada S., Konoeda Y., Maruyama H., Endo F., Kitagawa M., Tanimoto K., Hotta A., Tsuji T.

ACS Omega （ACS Omega） 9 （ 8 ） 9803 - 9812 2024年02月

Contact-killing antibacterial materials are attracting attention owing to their ability for sustained antibacterial activity. However, contact-killing antibacterial polystyrene (PS) has not been extensively studied because its chemically stable structure impedes chemical modification. In this study, we developed an antibacterial PS sheet with a contact-killing surface using PS synthesized from 2,2′-azobis-[2-(1,3-dimethyl-4,5-dihydro-1H-imi-dazol-3-ium-2-yl)]propane triflate (ADIP) as a radical initiator with cationic moieties. The PS sheet synthesized with ADIP (ADIP-PS) exhibited antibacterial activity in contrast to PS synthesized with other azo radical initiators. Surface ζ-potential measurements revealed that only ADIP-PS had a cationic surface, which contributed to its contact-killing antibacterial activity. The ADIP-PS sheets also exhibited antibacterial activity after washing. In contrast, PS sheets containing silver, a typical leachable antibacterial agent, lost all antibacterial activity after the same washing treatment. The antibacterial ADIP-PS sheet demonstrated strong broad-spectrum activity against both Gram-positive and Gram-negative bacteria, including drug-resistant bacteria. Cytotoxicity tests using L929 cells showed that the ADIP-PS sheets were noncytotoxic. This contact-killing antibacterial PS synthesized with ADIP thus demonstrated good prospects as an easily producible antimicrobial material.

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Blending Bottlebrush Polymers for Compensation of Orientation Birefringence of Polystyrene for Use as an Optical Polymer

Tamura M., Kurokawa N., Hotta A.

ACS Applied Polymer Materials （ACS Applied Polymer Materials） 5 （ 12 ） 10245 - 10255 2023年12月

For optical applications, including lenses, widely used polystyrene (PS) has not received much attention due to its considerably high birefringence. In this study, an efficient method was introduced to compensate for the orientation birefringence of PS through bottlebrush polymers with well-controlled PS graft chains (PS-BBP). PS-BBP were synthesized by ring-opening metathesis polymerization of norbornene-terminated PS macromonomers produced via atom transfer radical polymerization. Blend-film samples were then prepared by mixing linear PS and PS-BBP. One of the blend samples with a specific ratio of linear PS to PS-BBP (30:70) demonstrated extremely low orientation birefringence of |Δn| ∼3.9 × 10-4 even under 120% strain. In addition, the blend samples preserved almost the same refractive indices as linear PS, possessing the transparency required for optical polymers across the visible-wavelength range. The obtained PS blend could be utilized as an optical material with excellent optical properties.

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Multifunctionality of Iodinated Halogen-Bonded Polymer: Biodegradability, Radiopacity, Elasticity, Ductility, and Self-Healing Ability

Oyama Y., Kurokawa N., Hotta A.

ACS Biomaterials Science and Engineering （ACS Biomaterials Science and Engineering） 9 （ 11 ） 6094 - 6102 2023年11月

A polymer with high contents of ester bonds and iodine atoms was synthesized, exhibiting sufficient biodegradability and radioactivity for biomedical applications. The iodine moieties of the synthesized polyester can generate halogen bonding between molecules, which may develop additional functional properties through the bonding. In this study, poly(glycerol adipate) (PGA) was selected and synthesized as a polyester, which was then adequately conjugated with three different types of iodine compounds via the hydroxy groups of PGA. It was found that the iodine compounds could effectively work as donors of halogen bonding. The thermal analysis by differential scanning calorimetry (DSC) revealed that the glass transition temperature increased with the increase in the strength of interactions caused by π-π stacking and halogen bonding, eventually reaching 49.6 °C for PGA with triiodobenzoic groups. An elastomeric PGA with monoiodobenzoic groups was also obtained, exhibiting a high self-healing ability at room temperature because of the reconstruction of halogen bonding. Such multifaceted performance of the synthesized polyester with controllable thermal/mechanical properties was realized by halogen bonding, leading to a promising biomaterial with multifunctionality.

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Measurements of the Dissociation Heats of Tetrabutylammonium Acetate and Tetrabutylammonium Hydroxide Ionic Semiclathrate Hydrates

Iwai T., Takamura S., Hotta A., Ohmura R.

International Journal of Thermophysics （International Journal of Thermophysics） 44 （ 3 ） 2023年03月

ISSN 0195928X

Ionic semiclathrate hydrates mainly consist of water typically together with tetrabutylammonium and tetrabutylphosphonium salts. Since ionic semiclathrate hydrates have the large dissociation heat under ambient pressure and temperature conditions, various ionic semiclathrate hydrates have been studied as safety and eco-friendly phase change materials. In this study, tetrabutylammonium acetate hydrates and tetrabutylammonium hydroxide hydrates were proposed as thermal energy storage media for air conditioning and cooling lithium-ion batteries. The dissociation heat, which was a significant thermophysical property to design thermal energy storage systems, were measured at various mass fractions. The largest dissociation heats of tetrabutylammonium acetate hydrates and tetrabutylammonium hydroxide hydrates were 212.9 ± 0.9 kJ⋅kg−1 and 200.4 ± 2.2 kJ⋅kg−1. As a result of the comparison of the dissociation heats of tetrabutylammonium acetate hydrates and tetrabutylammonium hydroxide hydrates with those of other ionic semiclathrate hydrates, it was found that tetrabutylammonium acetate hydrates and tetrabutylammonium hydroxide hydrates had the promising thermophysical properties as thermal energy storage media for air conditioning and cooling lithium-ion batteries, respectively.

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Thermophysical Properties of Ionic Semiclathrate Hydrate Formed with Tetrabutylphosphonium Malonate

Iwai T., Oguro S., Ota I., Hiraga K., Hotta A., Ohmura R.

International Journal of Thermophysics （International Journal of Thermophysics） 44 （ 2 ） 2023年02月

ISSN 0195928X

Ionic semiclathrate hydrate is a crystalline compound mainly composed of water, which can dissociate at ordinary pressure and temperature. Ionic semiclathrate hydrates have been widely studied to develop prospective green and safety phase change materials utilized in a thermal energy storage system to cool batteries, in air conditioning, and in a cold chain system. The thermophysical properties, such as equilibrium temperature and dissociation heat, and the mass fraction dependence of such properties need to be carefully investigated to design such systems. In this study, the equilibrium temperature and the dissociation heat of tetrabutylphosphonium malonate ionic semiclathrate hydrates were experimentally determined at various mass fractions through an established method: the maximum value of the dissociation heat was 179.70 kJ·kg−1 at w = 0.357 and the equilibrium temperature was 8.9 °C at w = 0.357. By comparing tetrabutylphosphonium malonate ionic semiclathrate hydrates with other media in terms of the measured equilibrium temperature and the dissociation heat, the usability of the hydrates as thermal energy storage media for general air conditioning was discussed.

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β to α Form Transition Observed in the Crystalline Structures of Syndiotactic Polystyrene (sPS)

Ouchi T., Nagasaka S., Hotta A.

AIChE Annual Meeting, Conference Proceedings （AIChE Annual Meeting, Conference Proceedings） 2023-November 2112 - 2119 2023年

A solid-solid crystalline transition from β to α forms in syndiotactic polystyrene (sPS) was found during the mechanical deformation in the temperature range of 130-218 °C, studied by X-ray and infrared spectroscopy. α and β forms, in contrast to the other two crystalline structures (γ and δ forms) in sPS, are two major crystalline forms manufactured through a concise molding process which is industrially readily accessible. There have been a number of structural transitions found between two crystalline structures among the four different crystalline forms of sPS. In this work, β to α form transition at well below the melting temperature of sPS (~270 °C) was found by mechanical deformation, which became more pronounced as temperature increased. The structural transition was intimately related to the crystallization temperature and the densities of α and β forms.

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Synthesis and thermophysical properties of Tetrabutylammonium picolinate hydrate as an energy storage phase change material for cold chain

Yamamoto K., Iwai T., Hiraga K., Miyamoto T., Hotta A., Ohmura R.

Journal of Energy Storage （Journal of Energy Storage） 55 2022年11月

Ionic semiclathrate hydrates, the water-based phase change materials (PCMs) have potential for thermal energy storage media. There are a number of hydrates, reported in the literature, which are suitable as PCMs for air conditioning system of the required temperature range 10–15 °C. In this study, Tetrabutylammonium picolinate hydrate (TBAPi hydrate) was newly synthesized as a PCM for the cold chain, which has a lower phase equilibrium temperature than the previously reported hydrates. Thermophysical properties of TBAPi hydrate were experimentally measured. The hydrate dissociation heat was determined using a differential scanning calorimeter (DSC). The phase equilibrium temperature was measured by visually observing system with a CMOS camera and microscope. Also, the cycling test was conducted to confirm the long-term stability of thermophysical properties. The largest dissociation heat was 157.7 ± 4.9 kJ・kg−1 at a mass fraction of TBAPi aqueous solution, wTBAPi of 0.37. The highest phase equilibrium temperature of TBAPi hydrate was 5.5 °C at 0.34 ≤ wTBAPi ≤ 0.36. These thermophysical properties did not change even after 200 cycles of hydrate formation and dissociation. Based on the experimental results, TBAPi hydrate can be applied to the transport and storage of vaccines, blood packs, and perishable foods.

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Measurements of phase equilibrium temperature and dissociation heat of tetrabutylphosphonium glutarate ionic semiclathrate hydrate

Iwai T., Ohta I., Hiraga K., Kashima K., Hotta A., Ohmura R.

Fluid Phase Equilibria （Fluid Phase Equilibria） 562 2022年11月

ISSN 03783812

Thermophysical properties such as phase equilibrium temperature and dissociation heat are important to determine the performance of phase change materials targeting thermal energy storage. The phase equilibrium temperature and dissociation heat of tetrabutylphosphoniumglutarate ionic semiclathrate hydrate were measured in this study. The highest phase equilibrium temperature of tetrabutylphosphoniumglutarate hydrate was experimentally determined 287.4 K at the mass fraction 0.347 and 0.357. The largest dissociation heat was 193.3 ± 1.6 kJ/kg at the mass fraction 0.357. The measurement results in this work show that the dissociation heat can be utilized in the suitable temperature range targeting general air conditioning and data center.

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Numerical simulation of non-linear loading–unloading hysteresis behavior of blood clots

Tashiro K., Shobayashi Y., Hotta A.

Biocybernetics and Biomedical Engineering （Biocybernetics and Biomedical Engineering） 42 （ 4 ） 1205 - 1217 2022年10月

ISSN 02085216

The stress–strain characteristics of a clot during loading/unloading mechanical cycles are significant features to assess the underlying mechanisms of thrombectomy, especially when multiple thrombectomy attempts are required. We investigated a damage model to predict loading/unloading response of clots. To study the validity of the model, we tested theoretical models to reproduce the experimentally obtained mechanical characteristics of clots under various conditions. Three types of clot analogs with different red blood cell (RBC) compositions were prepared. Cylindrical clot analogs were formed for the tensile and compression tests. Loading/unloading tests at 80% of strain were conducted, where the material parameters were determined by fitting the results to a theoretical curve combining the damage model and the elasto-plastic constitutive model. Through the computation for theoretical curves, unique characteristics of clots were revealed such that the hysteresis loss rate did not change by varying RBC contents, except for the clot created with 0% RBC composition, under compressive loading. In addition, the plastic strain decreased as the RBC content decreased under tensile loading, whereas it increased as the RBC content decreased under compressive loading. A three-dimensional finite element method (FEM) was employed with the determined parameters. The FEM could accurately reproduce the experimental stress–strain curves for all types of clot analogs and for both loading types up to a strain of 80%. The results indicate that the theoretical model which incorporates and combines the damage model and the elasto-plastic constitutive model is applicable to predict the non-linear stress–strain behavior of clots under loading and unloading.

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Synthesis and evaluation of green phase change materials for efficient air conditioning by tetrabutylphosphonium phosphate ionic semiclathrate hydrate

Iwai T., Miyamoto T., Kurokawa N., Hotta A., Ohmura R.

Journal of Energy Storage （Journal of Energy Storage） 52 2022年08月

A tetrabutylammonium bromide (TBAB) hydrate is the only ionic semiclathrate hydrate that has been commercialized as a medium for efficient thermal energy storage targeting general air conditioning. However, TBAB is an environmental pollutant, while liquid water and ice that have been widely used as conventional media, also have difficulty in increasing the thermal energy storage density as well as the coefficient of performance (COP) of a refrigerator to form solid. In this study, a tetrabutylphosphonium phosphate ((TBP)3PO4) hydrate was proposed as an alternative green medium. The dissociation heat and the phase equilibrium temperature, which were both crucial factors to evaluate the thermal energy storage density, and COP was experimentally determined. It was found that the maximum dissociation heat was 154.1 ± 2.0 kJ・kg−1 at the mass fraction of 0.309. The highest phase equilibrium temperature was 10.0 °C at the mass fractions of 0.290, 0.299, and 0.309. The thermal energy storage density of (TBP)3PO4 hydrates was 3.7 times larger than that of water. (TBP)3PO4 hydrates increased the COP of a refrigerator to form solid by 42% as compared with ice, indicating the potential size-reduction of conventional devices with the decrease in the power consumption of a refrigerator. The effective balance between environmental protection and the system performance through (TBP)3PO4 hydrates was also discussed.

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Pinacol hydrate as a novel thermal energy storage medium for electric vehicles

Kiyokawa H., Kondo Y., Koyama R., Kurokawa N., Atsushi H., Alavi S., Ota I., Ohmura R.

Journal of Energy Storage （Journal of Energy Storage） 51 2022年07月

Movement towards the gradual replacement of gasoline combustion vehicles to electrical vehicles is occurring on a global scale. Heat management of lithium-ion batteries (LIB) is necessary for long-term operation and safety of the power sources of electrical vehicles. This research suggests pinacol hydrate as a phase change material (PCM) for use as an alternative cooling media for LIB. The pinacol hydrate crystallizes under atmospheric pressure and temperatures around 45 °C, which are compatible with LIB operating conditions. Its dissociation enthalpy can control the excessive heating of the battery. The equilibrium phase transition temperature of pinacol hydrate was reported about a decade ago, but its thermal storage capacity has not been reported yet and updated quantitative measurements are required. Hence, in this study the equilibrium temperatures and dissociation enthalpies are experimentally measured for pinacol aqueous solutions prepared with mass fractions between 0.40 and 0.85. The maximum thermal storage capacity is measured by differential scanning calorimetry to be 301.9 kJ/kg for mass fraction of 0.50 which is compatible with operating conditions of up to 45.6 °C. A minimization of reservoir tank mass by 35% of that needed for conventional technologies may be possible by using pinacol hydrate.

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Compensation for Orientation Birefringence of PMMA by Blending Bottlebrush Polymers Composed of Well-Controlled Graft Chains

Tamura M., Kurokawa N., Hotta A.

ACS Macro Letters （ACS Macro Letters） 11 （ 6 ） 799 - 804 2022年06月

The birefringence of optical polymers is a great issue in optical devices, inhibiting major applications of polymers to optical lenses and films. In this study, we have synthesized effective bottlebrush polymers with which we could attain almost zero birefringence when mixed with optical poly(methyl methacrylate) (PMMA). In detail, the PMMA bottlebrush polymers (PMMA-BBP) were synthesized by the ring-opening metathesis polymerization (ROMP) of norbornene-terminated PMMA macromonomers prepared via atom transfer radical polymerization (ATRP). Linear PMMA and PMMA-BBP were mixed to fabricate blend-film samples (PMMA/PMMA-BBP), which were uniaxially drawn to introduce molecular orientations. Linear PMMA possessed a negative value for its orientation birefringence, while the value of PMMA/PMMA-BBP increased as the PMMA-BBP content increased, whose orientation birefringence could reach almost zero when the ratio of the linear PMMA to PMMA-BBP became 73:27, regardless of the magnitude of the strain. The results reveal that the orientation birefringence of PMMA can be effectively controlled and removed by blending the appropriate content of PMMA-BBP.

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Highly-toughened and dimensionally-stable TEMPO cellulose nanofiber/bio-PBSA nanocomposites fabricated via Pickering emulsion process

Kurokawa N., Matsumoto K., Hotta A.

Composites Science and Technology （Composites Science and Technology） 223 2022年05月

ISSN 02663538

Bioplastic poly(butylene succinate-co-adipate) (PBSA) has several advantages because of its flexibility and high biodegradability. PBSA, however, possesses poor mechanical properties and dimensional instability. To overcome this, PBSA composites with TEMPO-oxidized cellulose nanofibers (TOCN/PBSA) were fabricated via the Pickering emulsion method. Porous bio-nanocomposite TOCN/PBSA mediums were made by the Pickering emulsion method, followed by the subsequent lyophilization to obtain TOCN/PBSA films by compression molding. It was confirmed that the Pickering-emulsion condition was a key factor to control the TOCN dispersion state in composite films. The Young's modulus of TOCN/PBSA composite films increased to 305 MPa at the TOCN concentration of 5 wt%, which was almost twice as high as that of pure PBSA. The studies on the morphology and tensile testing also revealed that the dispersion state of TOCNs was important to achieve excellent reinforcement effects and to suppress the fracture of composite films caused by stress concentration. The coefficient of thermal expansion at the TOCN concentration of 5 wt% was reduced to ∼25 × 10−5 K−1, half the value of pure PBSA. It was concluded that compounding TOCNs via the Pickering emulsion method was a very effective reinforcement method to improve the mechanical properties and the dimensional stability of PBSA.

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Morphology and mechanical property of quenched poly(L-lactide)/N,N-dimethylacetamide gels

Inukai S., Kurokawa N., Endo F., Maeda T., Hotta A.

Polymer （Polymer） 242 2022年03月

ISSN 00323861

Mechanically tough poly(L-lactide) (PLLA)/N,N-dimethylacetamide (DMAc) gels by rapid quenching using liquid nitrogen (LN) were synthesized. PLLA/DMAc solution at 110 °C was cooled at room temperature (PLLA-RT), or quenched by LN before keeping at RT (PLLA-LN). PLLA-RT with the PLLA concentrations of 5, 8, and 11 wt% did not form gel, while PLLA-RT with 14 and 17 wt% could form brittle gel exhibiting coarse structures. In contrast, PLLA-LN could form stable gel regardless of the PLLA concentration. The storage modulus of the gel with the PLLA concentration of 17 wt% increased from 78.7 kPa (PLLA-RT) to 563.7 kPa (PLLA-LN) at the strain of 0.1%. From the structural analysis, PLLA-RT formed spherulites (100–200 μm in diameter), whereas PLLA-LN formed relatively uniform network structures with continuous microporous skeletons without spherulites. The structural changes significantly contributed to the formation of stable, re-moldable, biodegradable, and biocompatible physical gels with ecofriendly and enhanced mechanical properties.

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Thermoset poly(2-methoxyethyl acrylate)-based polyurethane synthesized by RAFT polymerization and polyaddition

Tazawa S., Maeda T., Hotta A.

Materials Chemistry and Physics （Materials Chemistry and Physics） 278 2022年02月

ISSN 02540584

A solid poly(2-methoxyethyl acrylate) (PMEA)-based polyurethane (PU) has been synthesized through reversible addition−fragmentation chain transfer (RAFT) polymerization followed by polyaddition. PMEA with four hydroxyl-groups (PMEA-(OH)4) synthesized using RAFT reagents with 4 hydroxyl groups works as an effective prepolymer and crosslinker. The thermoset PMEA-based PU can be obtained by mixing PMEA-(OH)4 and diisocyanate without additional agents for the synthesis. The temperature-independent mechanical property of the thermoset PMEA-based PU due to the chemical crosslinking points is confirmed by dynamic mechanical analysis (DMA) at temperatures ranging from 25 °C to 110 °C. The mechanical property at room temperature is also evaluated by tensile testing: The Young's modulus of PMEA-based PU increased from 454 ± 31 kPa to 574 ± 54 kPa by decreasing Mn of the PMEA prepolymer from 14,000 to 7,600. It is concluded that our synthesized PMEA-based PU exhibits sufficiently elastomeric characteristics as compared with conventional crosslinked PMEA, which may be used as a durable and more stretchable biomedical material.

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Thermogelling Nanocomposite Hydrogel: PLGA Molecular Weight in PLGA-b-PEG-b-PLGA Affecting the Thermogelling Behavior

Maeda T., Tanimoto K., Hotta A.

Macromolecular Chemistry and Physics （Macromolecular Chemistry and Physics） 223 （ 1 ） 2022年01月

ISSN 10221352

Thermoresponsive gelation of the nanocomposites consisting of poly(lactic acid-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(lactic acid-co-glycolic acid) (PLGA-b-PEG-b-PLGA) triblock copolymers and LAPONITE (LAPONITE/PLGA-b-PEG-b-PLGA nanocomposites) is investigated by decreasing the molecular weights of PLGA as 1130, 900, and 470 g mol−1. As for the pure triblock copolymers, it is confirmed by UV–vis and SANS that a micellar structure with a hydrophobic core is formed even in the case of PLGA-b-PEG-b-PLGA with the lowest PLGA molecular weight of 470 g mol−1 (Triblock0.5k). As for the nanocomposites with LAPONITE, it is found that the gelation temperature (Tgel) becomes less dependent on the PLGA-b-PEG-b-PLGA concentration and more stable as the PLGA molecular weight decreases, and that Tgel of the nanocomposites almost linearly decreases as the LAPONITE concentration increases. Eventually, the nanocomposite with Triblock0.5k reaches Tgel between room temperature and physiological temperature. In addition, gradual degradation behavior is observed for the nanocomposite with Triblock0.5k. Considering the monomeric molecular weights of LA and GA at the LA/GA ratio of ≈2.0, it is concluded that the PLGA-b-PEG-b-PLGA with the lower PLGA molecular weight (i.e., Triblock0.5k) can be effectively used for thermoresponsive and degradable hydrogels targeting biomedical applications.

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Synthesis and thermophysical property evaluation of ionic semiclathrate hydrate formed with tetrabutylphosphonium glycine as a chilling temperature phase change material

Miyamoto T., Kurokawa N., Ota I., Hotta A., Ohmura R.

Journal of Energy Storage （Journal of Energy Storage） 45 2022年01月

Ionic semiclathrate hydrate, which is formed under atmospheric pressure with sustainably safe properties, has a potential for solid-liquid phase change materials(PCMs). In this study, the thermophysical property of tetrabutylphosphonium glycine(TBPGly) hydrate containing no halogen guest compound, glycine (aminoacetic acid), was investigated to evaluate the availability as an eco-efficient thermal energy storage medium. The phase equilibrium temperature was obtained through visual observation method. The heat flow rate curve behavior and dissociation heat were measured via differential scanning calorimetry(DSC). In the dissociation process, a single hydrate dissociation peak emerged, indicating TBPGly hydrate has one type of crystallographic structure. The concentration dependency of the TBPGly aqueous solution on the equilibrium temperature and the dissociation heat was confirmed. The highest equilibrium temperature of 5.8 °C was confirmed at the fraction range wTBPGly =0.368 or xTBPGly =0.0306, and the largest dissociation heat was 177.7 kJ·kg−1 at the fraction range wTBPGly =0.377or xTBPGly =0.0318. The estimated hydration number in the congruent composition was found to be in 31.2 to 32.5. In addition, based on the measured physical property, the optimum operating temperature and volume fraction of TBPGly hydrate was evaluated to determine the concentration for the practical cooling system. These data revealed TBPGly hydrate is available as a solid or slurry PCM under the operating temperature range 2 °C to 5.8 °C. The experimental data as well as the illustrative calculations contribute to accelerate the expansion in the application range, and provide the prospect in selecting the suitable composition toward the actual hydrate-based cooling system.

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Thermophysical Properties of a Promising Material for Thermal Energy Storage Synthesized by Tetrabutylphosphonium Malonate and Water

Iwai T., Oguro S., Ohta I., Hotta A., Ohmura R.

Proceedings of IEEE Asia-Pacific Conference on Computer Science and Data Engineering, CSDE 2022 （Proceedings of IEEE Asia-Pacific Conference on Computer Science and Data Engineering, CSDE 2022） 2022年

Thermal energy storage for air conditioning is increasingly becoming important because the fluctuating output of renewable energy and the growing cooling demand will need to be addressed. In this study, we proposed tetrabutylphosphonium malonate hydrate as an environment friendly thermal energy storage medium for air conditioning. Equilibrium temperature and dissociation heat, which were significant thermophysical properties for commercialization, were experimentally determined at three mass fractions of tetrabutylphosphonium malonate aqueous solution. The maximum value of equilibrium temperature was determined to be 8.9 °C. The largest dissociation heat was measured to be 148.1 kJ/kg. These results indicate that tetrabutylphosphonium malonate hydrate has appropriate thermophysical properties for a thermal energy storage medium.

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Investigation of the thermodynamic properties of hydrates as cooling phase change materials for their implementation in electric vehicles

Kiyokawa H., Miyamoto T., Takeya S., Ota I., Iwai T., Hotta A., Ohmura R.

New Journal of Chemistry （New Journal of Chemistry） 2022年

ISSN 11440546

Electric vehicles (EVs) play key roles in realizing a sustainable society. Lithium-ion batteries (LIBs) implemented in EVs deteriorate due to significant temperature changes. To maintain LIBs in an appropriate temperature range, a competitive thermal energy storage (TES) medium is needed. Phase change materials (PCMs) that can utilize their latent heat have great potential. In this study, we focused on piperazine hexahydrate as a promising candidate for a PCM and investigated its thermodynamic properties that are essential for practical design. The equilibrium temperature and dissociation enthalpy were determined in the mass fraction range of 0.250 to 0.550. The results showed that piperazine hexahydrate had a maximum equilibrium temperature of 42.9 °C and a maximum dissociation enthalpy of 250.0 ± 3.7 kJ kg−1 at a mass fraction of 0.443, which is the congruent point of piperazine hexahydrate. Piperazine hexahydrate can be utilized as a PCM in the temperature range of 34.4 °C to 42.9 °C. By utilizing piperazine hexahydrate instead of a conventional water-cooling system, the volume of the TES tank may be reduced by 31% approximately. The crystal system of the piperazine hexahydrate prepared in the present study was determined to be pseudomonoclinic by powder X-ray diffraction (PXRD) measurements, which is the same as that reported in the literature.

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The property of adhesion and biocompatibility of silicon and fluorine doped diamond-like carbon films

Toyonaga M., Hasebe T., Maegawa S., Matsumoto T., Hotta A., Suzuki T.

Diamond and Related Materials （Diamond and Related Materials） 119 2021年11月

ISSN 09259635

Application of nickel‑titanium (NiTi) alloys to medical implant devices is increasing due to their unique characteristics. However, many reports show adverse effects of corrosion of the alloys due to implantation in human body. To ensure good biocompatibility in the human body, fluorine-doped amorphous carbon (a-C:H:F) coating is a promising candidate. Generally, a-C:H:F coating shows poor adhesion on metallic alloys, so that silicon-incorporated interlayer is introduced between a-C:H:F and metallic alloys. However, this membrane design has a risk of delamination at the outermost interface (a-C:H:F//interlayer), and also there is a practical problem that coating time becomes long because the deposition process in multiple stages is required. Here we develop silicon and fluorine doped amorphous carbon (a-C:H:Si:F) film which exhibits high adhesion and excellent biocompatibility. One of the a-C:H:Si:F films “C2H2-doped”, which was deposited using a mixture of TMS, C2H2 and C3F8, showed higher adhesive strength than a-C:H:F with Si-interlayer and the same number of adhesive platelets and leukocytes as a-C:H:F. This result demonstrated that a single film with both adhesion of Si-interlayer and biocompatibility of a-C:H:F was fabricated. Furthermore, this a-C:H:Si:F coating can be anticipated as an effective film coating method in a practical point of view, because the film deposition is completed in one process.

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Controlling the switching temperature of biodegradable shape memory polymers composed of stereocomplex polylactide / poly(<inf>D,L</inf>-lactide-co-ε-caprolactone) blends

Hashimoto K., Kurokawa N., Hotta A.

Polymer （Polymer） 233 2021年10月

ISSN 00323861

We synthesized new biodegradable shape-memory polymers (SMPs) by blending synthesized poly(D,L-lactide-co-ε-caprolactone) (PLCL) and stereocomplex polylactide (sc-PLA) to be used as biomaterials for medical devices. PLCL copolymers (Mn ∼80,000) with various monomer ratios (LA:CL) were synthesized by the bulk ring-opening polymerization. The glass transition temperature of the resulting PLCL copolymers could be well controlled from −3 °C to 60 °C, agreeing well with the values by the Gordon-Taylor equation, confirming the homogeneous random distribution of LA and CL monomers in the synthesized PLCL. The synthesized PLCL and sc-PLA were eventually blended for the fabrication of biodegradable SMPS. The PLCL/sc-PLA blend samples possessed the sc-PLA crystallinity of ∼13%, which effectively worked as crosslinkings, exhibiting shape-memory behavior with various switching temperatures (30.5°C–62 °C) and shape-recovery ratios realized by adjusting the CL ratio of the PLCL copolymers: a lower CL ratio resulted in a higher switching temperature and a higher shape-recovery ratio.

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Finite element analysis of blood clots based on the nonlinear visco-hyperelastic model

Tashiro K., Shobayashi Y., Ota I., Hotta A.

Biophysical Journal （Biophysical Journal） 120 （ 20 ） 4547 - 4556 2021年10月

ISSN 00063495

Mechanical thrombectomy has become the standard treatment for patients with an acute ischemic stroke. In this approach, to remove blood clots, mechanical force is applied using thrombectomy devices, in which the interaction between the clot and the device could significantly affect the clot retrieval performance. It is expected that the finite element method (FEM) could visualize the mechanical interaction by the visualization of the stress transmission from the device to the clot. This research was aimed at verifying the constitutive theory by implementing FEM based on the visco-hyperelastic theory, using a three-dimensional clot model. We used the visco-hyperelastic FEM to reproduce the mechanical behavior of blood clots, as observed in experiments. This study is focused on the mechanical responses of clots under tensile loading and unloading because in mechanical thrombectomy, elongation is assumed to occur locally on the clots during the retrieval process. Several types of cylindrical clots were created by changing the fibrinogen dose. Tensile testing revealed that the stiffness (E0.45-value) of clots with fibrinogen could be more than three times higher than that of clots without fibrinogen. It was also found that the stiffness was not proportional to the fibrinogen dose. By fitting to the theoretical curve, it was revealed that the Mooney-Rivlin model could reproduce the hyperelastic characteristics of clots well. From the stress-relaxation data, the three-chain Maxwell model could accurately fit the experimental viscoelastic data. FEM, taking the theoretical models into account, was then carried out, and the results matched well with the experimental visco-hyperelastic characteristics of clots under tensile load, reproducing the mechanical hysteresis during unloading, the stress dependence on the strain rate, and the time-dependent stress decrease in the stress-relaxation test.

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Article mechanical property of polypropylene gels associated with that of molten polypropylenes

Ouchi T., Yamazaki M., Maeda T., Hotta A.

Gels （Gels） 7 （ 3 ） 2021年09月

This study aims to understand the fundamental mechanical relationship between polypropy-lene (PP)-gels and solid PPs without solvent through mechanical and thermal analyses, by which the mechanical similarities between molten PPs and PP gels were found, leading to the reliable estimate of the mechanical properties of semi-crystalline gels. The gelation of syndiotactic and isotactic polypropylenes (sPP and iPP) was found when PPs were dissolved in 1,2,3,4-tetrahydronaphthalene (tetralin). Interestingly, it was found that the storage modulus of sPP-gel became higher than that of iPP-gel at low PP concentration (<~40 wt%). The result was distinctly different from the result of neat solid PPs (without solvent), where the modulus of solid sPP is generally significantly lower than that of solid iPP. Such inversion behavior in the mechanical property of semi-crystalline gels had not been reported and discussed before. By further investigation of the storage moduli of neat sPP and iPP, it was found that the storage modulus of sPP became higher than that of iPP above the melting points of PP, which was similar to the behavior of the storage moduli observed in the diluted PP-gels. Such similarity between PP-gels and PP melts was also observed within iPP samples with different molecular weights.

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Antithrombogenic poly(2-methoxyethyl acrylate) elastomer via triblock copolymerization with poly(methyl methacrylate)

Kurokawa N., Endo F., Bito K., Maeda T., Hotta A.

Polymer （Polymer） 228 2021年07月

ISSN 00323861

For the development of blood-contacting biomedical devices, preventing platelet adhesion and avoiding subsequent thrombosis through antithrombogenic surface are vitally important. Poly (2-methoxyethyl acrylate) (PMEA) is a synthetic viscous polymer with an excellent antithrombogenic property, which has already been used as an antithrombogenic coating for biomedical purposes. The PMEA coating, however, can be easily broken due to its liquid-like feature, since the glass transition temperature (Tg) of PMEA is at −25οC. Solidifying PMEA has, therefore, been desperately desired for the improvement of the stability of PMEA coating. Also, once solidified, PMEA could be utilized not only for coating but also for structural materials for medical devices, expanding the application range of PMEA. In this study, PMEA was first solidified by triblock copolymerization with poly (methyl methacrylate) (PMMA) to obtain thermoplastic elastomers with excellent antithrombogenicity. We synthesized PMMA-PMEA-PMMA triblock copolymers with different volume fractions of PMMA (fMMA) by atom transfer radical polymerization (ATRP). The synthesis and the chemical structures of the new triblock copolymers were characterized and confirmed by proton nuclear magnetic resonance (1H NMR) analyses and gel permeation chromatography (GPC). The synthesized elastomeric triblocks were then compression-molded at 180οC to obtain solid transparent films. The tensile property was measured and the drastic change from the soft-elastomer phase to the hard-plastic phase was clearly observed by varying fMMA. It was found that the new triblocks possessed significantly higher tensile strengths than the other solidified PMEA by the previous studies. The platelet adhesion test revealed that the number of adherent platelets on the triblocks with fMMA of 0.12 and 0.40 was almost the same as that on pure PMEA, indicating that the synthesized triblocks possessed excellent antithrombogenicity similar to liquid PMEA. Further investigation on hydrated water and microphase-separated structures eventually revealed that the new triblock copolymers with a sufficient amount of intermediate water or with microphase separation on the surface resulted in excellent antithrombogenicity.

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Fabrication of Gd-DOTA-functionalized carboxylated nanodiamonds for selective MR imaging (MRI) of the lymphatic system

Yano K., Matsumoto T., Okamoto Y., Kurokawa N., Hasebe T., Hotta A.

Nanotechnology （Nanotechnology） 32 （ 23 ） 2021年06月

ISSN 09574484

Magnetic resonance imaging (MRI) contrast agents with the particle diameter of around 3-10 nm hold the potential to be selectively uptaken by lymphatic vessels and be filtered in the kidney for final excretion. However, there are no existing MRI contrast agents based on gadolinium (Gd) complexes within the size of this range, and thus the selective imaging of the lymphatic system has not yet been achieved. In our previous report, we succeeded in fabricating nano-scale MRI contrast agents by complexing ordinary contrast agents (Gd-diethylenetriaminepentaacetic acid (DTPA)) with carboxylated nanodiamond (CND) particles to conquer this problem. However, DTPA has recently been reported to release Gd ions in the course of time, leading to the potential danger of severe side effects in the human body. In this study, we utilized cyclic-chained DOTA as an alternative chelating material for DTPA to fabricate CND-based MRI contrast agents for the selective lymphatic imaging. The newly fabricated contrast agents possessed the diameter ranging from 3 to 10 nm in distilled water and serum, indicating that these particles can be selectively uptaken by lymphatic vessels and effectively filtered in the kidney. Furthermore, the DOTA-applied CND contrast agents exhibited stronger MRI visibility in water and serum compared to DTPA-applied CND contrast agents. These results indicate that DOTA-applied CND contrast agents are promising materials for the selective MR imaging of lymphatic systems.

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Degradation of thermoresponsive laponite/PEG-b-PLGA nanocomposite hydrogels controlled by blending PEG-b-PLGA diblock copolymers with different PLGA molecular weights

Maeda T., Kitagawa M., Hotta A.

Polymer Degradation and Stability （Polymer Degradation and Stability） 187 2021年05月

ISSN 01413910

The thermoresponsive gelation behavior and the degradation behavior of the nanocomposites consisting of poly(ethylene glycol)-b-poly(lactic acid-co-glycolic acid) (PEG-b-PLGA) diblock copolymers and clay nanoparticles (laponite) (laponite/PEG-b-PLGA nanocomposites) were studied by changing the blend ratio of the PEG-b-PLGA diblock copolymers using different PLGA molecular weights of 800 g/mol and 1600 g/mol: PEG-b-PLGA (1000-800, Diblock0.8k) and PEG-b-PLGA (1000-1600, Diblock1.6k). It was found that each gelation temperature was in the temperature range between 25°C and 37°C, when the PEG-b-PLGA concentration and the laponite concentration were kept at 3–4 wt% and 1 wt%, respectively. The degradation rate at 37°C was found to be effectively regulated by the Diblock1.6k/Diblock0.8k blend ratio (DR). In detail, after 15 days of the degradation experiments, the weight loss was decreased by ∼14% when DR changed from DR=0/100 to DR=100/0. It was, therefore, confirmed that DR was the key parameter to control the degradation behavior of the laponite/blended PEG-b-PLGA nanocomposites.

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Mechanical, thermal, and microstructural analyses of thermoplastic poly(2-methoxyethyl acrylate)-based polyurethane by RAFT and polyaddition

Tazawa S., Maeda T., Hotta A.

Materials Advances （Materials Advances） 2 （ 5 ） 1657 - 1664 2021年03月

Mechanical and thermal properties of the newly synthesized solid poly(2-methoxyethyl acrylate) (PMEA)-based polyurethane (PU) were studied. The obtained PMEA-based PUs with various molecular weights were thermoplastic, synthesized by reversible addition-fragmentation chain transfer (RAFT) and polyaddition. Dynamic mechanical analysis (DMA) revealed that the storage modulus and the melting temperature of PMEA-based PU significantly increased from 1.5 × 104 Pa to 2.3 × 105 Pa and from 25 °C to 73 °C, respectively, as the molecular weight of PMEA-based PU increased. This enhancement in the properties could be due to the formation of an ordered structure in PMEA-based PU, studied using small-angle and wide angle X-ray scattering (SAXS, WAXS). Glass transition temperature, 5% weight-reduction temperature, and the amount of intermediate water of PMEA-based PU were also analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). This journal is

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Gadolinium-Complexed Carboxylated Nanodiamond Particles for Magnetic Resonance Imaging of the Lymphatic System

Yano K., Matsumoto T., Okamoto Y., Bito K., Kurokawa N., Hasebe T., Hotta A.

ACS Applied Nano Materials （ACS Applied Nano Materials） 4 （ 2 ） 1702 - 1711 2021年02月

MRI contrast agents with a size of 3-10 nm are considered to be an effective pathway for selective MR lymphatic imaging. In our previous study, we fabricated nanosized MRI contrast agents (Gd-DTPA-ND) with the condensation of nanodiamond (ND) particles and gadolinium chelates (Gd-DTPA). However, these Gd-DTPA-ND particles formed microscale aggregates in distilled water, exceeding the size required for selective lymphatic MR imaging. In this study, carboxylated nanodiamond (CND) particles were utilized as alternative platforms for condensation with gadolinium complexes. The carboxyl groups introduced by oxidation were expected to induce hydrophilicity with a negative charge on the ND surface, resulting in the high dispersity of gadolinium-complexed CND particles. The fabricated Gd-DTPA-CND particles possessed a hydrodynamic diameter of around 4-5 nm without any signs of aggregation in distilled water and human serum. Furthermore, the T1-weighted image of Gd-DTPA-CND particles in distilled water and human serum presented strong contrast, indicating the excellent MRI visibility of the particles. Therefore, the Gd-DTPA-CND particles can become practical MRI contrast agents for the achievement of selective MR imaging of the lymphatic system.

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Structures and mechanical properties of electrospun cellulose nanofibers/poly(ε-caprolactone) composites

Taniguchi H., Kurokawa N., Inukai S., Hotta A.

Journal of Applied Polymer Science （Journal of Applied Polymer Science） 137 （ 42 ） 2020年11月

ISSN 00218995

© 2020 Wiley Periodicals, Inc. Poly(ε-caprolactone) (PCL) is one of the ecofriendly biodegradable polymers with excellent moldability but with rather low mechanical properties especially for the industrial and biomedical use. In this research, to overcome the problem, the two types of cellulose nanofibers, the cellulose acetate nanofibers (CA-NF) and the cellulose nanofibers (C-NF), were composited into PCL for the enhancement of the mechanical properties of PCL. CA-NF were prepared by electrospinning and converted into C-NF afterward by deacetylation. It was found that the Young's modulus of the CA-NF/PCL composite at the fiber concentration of 35 wt% significantly increased by ~3 times as compared with that of neat PCL, whereas C-NF/PCL of the same fiber concentration also increased by ~4.5 times. It was also found that the Young's moduli of CA-NF/PCL nearly reached the theoretical values calculated by the equation suggested by Tsai, but that the Young's moduli of C-NF/PCL could not reach the theoretical values. It indicates that CA-NF possessed better compatibility with PCL than C-NF, agreeing well with the fracture-surface analyses of the two composites by the scanning electron microscopy.

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Synthesis of Thermoplastic Poly(2-methoxyethyl acrylate)-Based Polyurethane by RAFT and Condensation Polymerization

Tazawa S., Maeda T., Nakayama M., Hotta A.

Macromolecular Rapid Communications （Macromolecular Rapid Communications） 41 （ 19 ） 2020年10月

ISSN 10221336

© 2020 Wiley-VCH GmbH Thermoplastic solid poly(2-methoxyethyl acrylate) (PMEA)-based polyurethane (PU) is synthesized through the reversible addition−fragmentation chain transfer (RAFT) polymerization and the condensation polymerization, using hydroxyl-terminated RAFT reagents and diisocyanate, respectively. Neat PMEA is a promising antithrombogenic liquid used in the medical fields. The thermoplastic property of the solid PMEA-based PU due to hydrogen bonding is confirmed by the dynamic mechanical analysis (DMA) at temperature below 72 °C. The antithrombogenic property of PMEA-based PU is also analyzed by the platelet adhesion test. The number of platelets on PMEA-based PU is 17 cells per unit area, which is smaller than that on the fluorinated diamond-like carbon (F-DLC), a well-known highly antithrombogenic material. It is concluded that a newly synthesized PMEA-based PU exhibits thermoplastic characteristics with excellent antithrombogenicity.

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Evaluation of Crystallinity and Hydrogen Bond Formation in Stereocomplex Poly(lactic acid) Films by Terahertz Time-Domain Spectroscopy

Hirata J., Kurokawa N., Okano M., Hotta A., Watanabe S.

Macromolecules （Macromolecules） 53 （ 16 ） 7171 - 7177 2020年08月

ISSN 00249297

Copyright © 2020 American Chemical Society. Stereocomplex poly(lactic acid) (sc-PLA) crystallites exhibit higher mechanical strength and thermal stability than PLA homocrystallites. In sc-PLA, a hydrogen bond that governs the physical properties is formed between two enantiomeric PLA chains during crystallization. Therefore, the investigation of this hydrogen bond is essential for a better understanding of the properties of sc-PLA. Here, we report on the terahertz spectroscopy of sc-PLA films with low crystallinities. The dielectric function in the terahertz regime allows us to estimate the crystallinity of sc-PLA because various intra- and intermolecular vibration modes lie in the terahertz frequency range. By comparison with X-ray diffraction measurements, the validity of the crystallinity evaluation based on terahertz spectroscopy is verified. Furthermore, a remarkable red-shift of the peak in the imaginary part of the dielectric function occurs as the crystallinity increases. By comparison with Fourier transform infrared spectroscopy, it is considered that this red-shift is caused by the anharmonic nature of the vibrational potential corresponding to the intermolecular libration mode of the sc-PLA crystallites. The hydrogen bond formation associated with the sc-PLA crystallization increases the anharmonicity of the vibrational potential of sc-PLA, and then the red-shift of the peak occurs. Our findings suggest that structural changes due to the stereocomplexation can be sensitively probed by terahertz spectroscopy.

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Thermophysical Property Measurements of Tetrabutylphosphonium Oxalate (TBPOx) Ionic Semiclathrate Hydrate as a Media for the Thermal Energy Storage System

Miyamoto T., Koyama R., Kurokawa N., Hotta A., Alavi S., Ohmura R.

Frontiers in Chemistry （Frontiers in Chemistry） 8 2020年07月

© Copyright © 2020 Miyamoto, Koyama, Kurokawa, Hotta, Alavi and Ohmura. With increasing global power demand, thermal energy storage technology could play a role ensuring a sustainable energy supply in power generation from renewable energy sources and power demand concentration. Hydrates have high potential as phase change materials (PCMs) for the use as a thermal energy storage medium. To develop thermal energy storage technology using a hydrate-based material, further investigation of thermophysical properties and the selection of a suitable hydrate are required. Tetrabutylphosphonium oxalate (TBPOx) ionic semiclathrate hydrate contains oxalic acid in salt form, as a guest compound, which is classified as carboxylic acid group with low environmental impact. In the present study, the phase equilibrium temperature and the dissociation heat of TBPOx hydrate were measured. The highest equilibrium temperature of the solid hydrate formed was 9.4°C at the mass fraction 0.35 of TBPOx in aqueous solution. The largest dissociation heat was 186.0 ± 0.5 kJ·kg−1 at the mass fraction of 0.35. Comparing with other PCMs with close phase equilibrium temperatures, TBPOx hydrate is superior in safety and sustainability. These results indicate that TBPOx hydrate would be suitable as the thermal storage medium for the general air conditioning systems.

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Mechanical properties of poly(ε-caprolactone) composites with electrospun cellulose nanofibers surface modified by 3-aminopropyltriethoxysilane

Inukai S., Kurokawa N., Hotta A.

Journal of Applied Polymer Science （Journal of Applied Polymer Science） 137 （ 17 ） 2020年05月

ISSN 00218995

© 2019 Wiley Periodicals, Inc. To enhance the reinforcement effects of regenerated cellulose nanofibers (RC-NF) in poly(ε-caprolactone) (PCL), we synthesized RC-NF-3-aminopropyltriethoxysilane (APS), the surface-modified RC-NF by APS. The RC-NF were fabricated by the saponification of electrospun cellulose–acetate nanofibers. The surface modification by APS was confirmed by the X-ray photoelectron spectroscopy (XPS). To enhance the mechanical property of PCL, the RC-NF and the RC-NF-APS were separately compounded into PCL by compression molding. It was found that, when the fiber concentration of RC-NF-APS was 17 wt %, the Young's modulus at room temperature increased from 698.0 to 744.7 MPa, whereas the storage modulus at 55 °C almost increased from 180 to 220 MPa. The micrographs of the fracture surface of the composites revealed that the surface modification prevented the pull-out of RC-NF from PCL. It was concluded that the mechanical properties of the composites were enhanced due to the improvement of the compatibility between RC-NF and PCL by the surface modification with APS. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48599.

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Fabrication of radiopaque drug-eluting beads based on Lipiodol/biodegradable-polymer for image-guided transarterial chemoembolization of unresectable hepatocellular carcinoma: Fabrication of radiopaque DEBs by Lipiodol/biodegradable-polymer for TACE of HCC

Okamoto Y., Hasebe T., Bito K., Yano K., Matsumoto T., Tomita K., Hotta A.

Polymer Degradation and Stability （Polymer Degradation and Stability） 175 2020年05月

ISSN 01413910

© 2020 Elsevier Ltd New radiopaque/biodegradable drug-eluting beads (DEBs) for transarterial chemoembolization (TACE) were fabricated using Lipiodol and polycaprolactone (PCL) (Lipiodol/PCL beads) through a microfluidic device. TACE is the most extensively-applied therapy for unresectable hepatocellular carcinoma (HCC). DEBs are embolic microspheres with sustained and tumor-selective drug-delivery characteristics for tumor-feeding arteries. As the conventional DEBs are not radiopaque by themselves and not biodegradable, it is difficult to monitor bead localization and attenuation through CT images after DEB-TACE procedures, and the complication after non-target embolization becomes potentially more serious. In this work, we found that our new biodegradable Lipiodol/PCL lost 63.5% of their weight 11 days after immersion, simultaneously releasing 0.94 μg of miriplatin (a lipophilic platinum-based anticancer drug) from the Lipiodol/PCL beads in 11 days. We also found that the degradation speed could be controlled from 18.2% to 63.5% of the weight loss in 11 days by changing the molecular weight of PCL and the ratio of Lipiodol/PCL. The mean diameter of the bead could be well controlled by changing the flow-rate ratio of the microfluidic device. Regarding the radiopacity in vitro, the Lipiodol/PCL beads were clearly visualized through CT imaging, with a mean attenuation of over 5600 HU. Furthermore, it was found from the radiopacity experiments in vivo, that the embolization by the Lipiodol/PCL beads in the rabbit vessel was clearly recognized through CT images, indicating high potential of the newly synthesized biodegradable beads to improve the current TACE procedures by providing refined locational information on drug and embolic particles.

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Equilibrium temperature and dissociation heat of tetrabutylphosphonium acrylate (TBPAc) ionic semi-clathrate hydrate as a medium for the hydrate-based thermal energy storage system

Koyama R., Hotta A., Ohmura R.

Journal of Chemical Thermodynamics （Journal of Chemical Thermodynamics） 144 2020年05月

ISSN 00219614

© 2020 The hydrate-based thermal energy storage system is one of the most effective supplemental technologies to stabilize the energy supply for renewable energies. The system is expected to solve the global energy-management issues related to energy-demand increase and energy supply chain. In fact, this eco-friendly technology requires prospective hydrate candidates for the thermal energy storage media, followed by the extensive investigation of the thermophysical properties of the selected hydrates. In this study, to satisfy these requirements, the equilibrium temperature and the dissociation heat of tetrabutylphosphonium acrylate (TBPAc) ionic semi-clathrate hydrate were studied. It was found that the highest equilibrium temperature was 14.4 °C at the mass fractions from 0.37 to 0.40. It was also found that the largest dissociation heat was (210.4 ± 5.3) kJ kg−1 at the mass fraction 0.39. These values indicate that TBPAc hydrate could be a new promising thermal-storage medium for the general or data-centre air-conditioning systems. The experimental results of this study also revealed an underlying tendency between the thermophysical properties of the tetrabutylphosphonium (TBP) + carboxylate salt hydrates and the molar mass of the guest anion in salt.

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Regenerated cellulose nanofibers fabricated through electrospinning and saponification of cellulose acetate as reinforcement of polylactide composites

Kurokawa N., Hotta A.

Cellulose （Cellulose） 26 （ 13-14 ） 7797 - 7808 2019年09月

ISSN 09690239

© 2019, Springer Nature B.V. Cellulose-acetate nanofibers (CA-NF) and regenerated cellulose nanofibers (RC-NF) were separately compounded as reinforcement materials for enhancement of the mechanical property of polylactide (PLA). PLA has a great potential as an alternative to widely-used plastics such as polystyrene and poly(ethylene terephthalate), which are made from petroleum. PLA is well known for its biodegradability and renewability, but the mechanical property of PLA is not sufficient for industrial applications. In this study, CA-NF were successfully fabricated by electrospinning using 20 wt% cellulose-acetate solution with acetone/N,N-dimethylacetamide (6/4, wt/wt) mixture solvent, and RC-NF were synthesized by subsequent saponification, as reinforcement materials for PLA composites. The Young’s modulus of CA-NF/PLA composites increased linearly from 1670 to 1840 MPa with the increase in the nanofiber concentration to 15 wt%. In contrast, the Young’s modulus of RC-NF/PLA composites rapidly increased to ~ 1840 MPa at the relatively low nanofiber concentration of 5.0 wt%. Above 5.0 wt%, the Young’s modulus became stable and almost constant. RC-NF exhibited better reinforcing efficiency due to the excellent mechanical property of RC-NF, although the interfacial compatibility of RC-NF for PLA matrix was relatively poor as compared with that of CA-NF.

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SANS study on the nano-crystalline network structure of elastic physical gels made of syndiotactic polypropylene

Endo F., Kurokawa N., Tanimoto K., Iwase H., Maeda T., Hotta A.

Soft matter （Soft matter） 15 （ 27 ） 5521 - 5528 2019年07月

The structure-property relationship of an elastic physical gel, obtained by simply quenching syndiotactic polypropylene (sPP)/decahydronaphthalene solution with liquid nitrogen, was investigated based on small-angle neutron scattering (SANS) analysis. The SANS analysis revealed that sPP nanocrystals with a constant radius of 4-5 nm existed in the sPP gels regardless of the sPP concentration, whereas the correlation length of the nanocrystals drastically decreased from ∼130 to ∼20 nm upon increasing the sPP concentration from 2 to 12 wt%. The volume fraction and the number density of the sPP nanocrystals increased monotonously with the increase in the sPP concentration. The rheological properties and the melting behavior of the quenched sPP gels were highly consistent with the number density of the nanocrystals calculated from the SANS analysis, strongly suggesting that the sPP nanocrystals actually worked as crosslinking points by inducing elasticity in the quenched sPP gels.

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Thermophysical properties of trimethylolethane (TME) hydrate as phase change material for cooling lithium-ion battery in electric vehicle

Koyama R., Arai Y., Yamauchi Y., Takeya S., Endo F., Hotta A., Ohmura R.

Journal of Power Sources （Journal of Power Sources） 427 70 - 76 2019年07月

ISSN 03787753

© 2019 Elsevier B.V. Management for the temperature increase of lithium-ion batteries in electric vehicles (EV) is required for safety and energy efficiency. As a cooling medium for lithium-ion batteries, one suitable candidate is trimethylolethane (TME) hydrate, which may be utilized as a phase change material (PCM). This hydrate has a large dissociation heat and will form/dissociate at approximately 30 °C under atmospheric pressure conditions. A cooling system which uses TME hydrate can have a high performance with regards to the efficiency and the stability of heat transfer process. However, in previous studies, the equilibrium temperature and the dissociation heat of TME hydrate have been reported only for a TME mass fraction of 0.625. Since TME hydrate forms in an aqueous solution, it is necessary to know how these thermophysical properties change for a range of TME mass fractions. Therefore, in this study, the equilibrium temperatures and the dissociation heats were measured respectively by the visual observation method and differential scanning calorimetry measurements for TME mass fraction range from 0.20 to 0.80. The highest equilibrium temperature was 29.6 °C at the mass fraction of 0.60. For the cooling system, the largest dissociation heat was 190.1 kJ kg−1, also at the mass fraction of 0.60.

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Controlling the size of spherulite and the degradation of poly(butylene succinate-co-adipate) by solvent and gel preparation temperature

Yamazaki H., Kamitabira S., Maeda T., Hotta A.

Polymer Degradation and Stability （Polymer Degradation and Stability） 162 106 - 111 2019年04月

ISSN 01413910

© 2019 Elsevier Ltd The size of spherulites observed in the poly(butylene succinate-co-adipate) (PBSA) gel was found to be effectively controlled by the careful selection of the types of solvent and the gel preparation temperature. Additionally, the degradation behavior of the PBSA dried-gels with different sizes of spherulites was studied. By using different solvents, such as toluene (TOL), o-dichlorobenzene (o-DCB), and cyclohexanone (CHN), the diameter of the spherulites could be changed from 16.7 μm to 186.2 μm, while the gel preparation temperature was kept constant at 28 °C. The gel preparation temperature was then changed from −50 °C to 28 °C using CHN, and it was found that the diameter of the spherulites changed from 25.2 μm to 186.2 μm. Regarding the degradation behavior, the PBSA dried-gel with relatively smaller spherulites (∼20 μm in diameter) exhibited higher weight loss of over 80% at the immersion time of 6 days, while the PBSA dried-gels with relatively larger spherulites (∼186 μm in diameter) presented lower weight loss of below 30% at the immersion time of 6 days. It was therefore concluded that the degradation rate became lower with the increase in the size of spherulites.

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Thermophysical property measurements on tetrabutylphosphonium sulfate ionic semiclathrate hydrate consisting of the bivalent anion

Arai Y., Koyama R., Endo F., Hotta A., Ohmura R.

Journal of Chemical Thermodynamics （Journal of Chemical Thermodynamics） 131 330 - 335 2019年04月

ISSN 00219614

© 2018 Elsevier Ltd To develop the “hydrate thermal energy storage technology” it is desired to reveal the mechanism of the thermophysical property manifestation on ionic semiclathrate hydrate. The influence of valence on thermophysical properties has not been investigated so far. In the present study, the phase equilibrium temperatures and the dissociation heats of tetrabutylphosphonium sulfate ((TBP)2SO4) ionic semiclathrate hydrate were experimentally studied. (TBP)2SO4 hydrate consists of the bivalent anion, SO42−. The highest phase equilibrium temperature was 6.5 °C at the mass fraction range from 0.363 to 0.384. The largest dissociation heat was (168.8 ± 2.4) kJ·kg−1 at the mass fraction 0.374. These values of the phase equilibrium temperature and the dissociation heat were respectively lower and smaller than those of the ionic semiclathrate hydrates with the monovalent anion. As a new choice for thermal energy storage medium, (TBP)2SO4 hydrate would be suitable to the automotive air conditioner and the cold chain for blood or perishable foods.

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Micropatterning of a 2-methacryloyloxyethyl phosphorylcholine polymer surface by hydrogenated amorphous carbon thin films for endothelialization and antithrombogenicity

Bito K., Hasebe T., Maegawa S., Kitagawa T., Matsumoto T., Suzuki T., Hotta A.

Acta Biomaterialia （Acta Biomaterialia） 87 187 - 196 2019年03月

ISSN 17427061

© 2019 Acta Materialia Inc. The existing first-generation drug-eluting stent (DES) has caused late and very late stent thrombosis related to incomplete stent endothelialization. Hence, biomaterials that possess sufficient anti-thrombogenicity and endothelialization with the controlled drug release system have been highly required. In this work, we have developed a newly designed drug-release platform composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, a non-thrombogenic polymer, and micropatterned hydrogenated amorphous carbon (a-C:H), a cell-compatible thin film. The platelet adhesion and the endothelial cell adhesion behavior on the micropatterned substrates were investigated in vitro. The results indicated that the micropatterned a-C:H/MPC polymer substrates effectively supported the human umbilical vein endothelial cell (HUVEC) proliferation, while suppressing the platelet adhesion. Interestingly, the HUVEC exhibited different shape and behavior by changing the island size of the micropatterned a-C:H. By introducing both a non-thrombogenic polymer and cell-compatible thin films through a simple patterning method, we demonstrated that the platform had the potential to be utilized as a base material for DES with cell controllability. Statement of significance: The current first-generation drug-eluting stents (DES) would cause late and very late stent thrombosis due to the incomplete endothelialization of the metal stent material. In this work, we have developed a new DES platform composed of a 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer micropatterned by hydrogenated amorphous carbon (a-C:H). Two types of differently micropatterned a-C:H stent surface were made. Our studies revealed that the micropatterned a-C:H/MPC polymer substrates could effectively enhance the endothelial cell (EC) proliferation, simultaneously suppressing the platelet adhesion, becoming a highly biocompatible material especially for indwelling devices including a drug-release device. The new drug-release platform could be utilized as a base material for cell-controllable coating on DES.

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Thermo-responsive nanocomposite hydrogels based on PEG-b-PLGA diblock copolymer and laponite

Maeda T., Kitagawa M., Hotta A., Koizumi S.

Polymers （Polymers） 11 （ 2 ） 2019年02月

© 2019 by the authors. Poly(ethylene glycol)-b-poly(D,L-lactide-co-glycolide) (PEG-b-PLGA) diblock copolymers are widely known as polymeric surfactants for biomedical applications, and exhibit high solubility in water compared to PLGA-b-PEG-b-PLGA triblock copolymers known as gelation agents. In order to overcome the difficulties in the preparation of thermo-responsive hydrogels based on PLGA-b-PEG-b-PLGA due to the low solubility in water, the fabrication of thermo-responsive hydrogels based on PEG-b-PLGA with high solubility in water was attempted by adding laponite to the PEG-b-PLGA solution. In detail, PEG-b-PLGA with high solubility in water (i.e., high PEG/PLGA ratio) were synthesized. Then, the nanocomposite solution based on PEG-b-PLGA and laponite (laponite/PEG-b-PLGA nanocomposite) was fabricated by mixing the PEG-b-PLGA solutions and the laponite suspensions. By using the test tube inversion method and dynamic mechanical analysis (DMA), it was found that thermo-responsive hydrogels could be obtained by using PEG-b-PLGA, generally known as polymeric surfactants, and that the gelation temperature was around the physiological temperature and could be regulated by changing the solution composition. Furthermore, from the structural analysis by small angle neutron scattering (SANS), PEG-b-PLGA was confirmed to be on the surface of the laponite platelets, and the thermosensitive PEG-b-PLGA on the laponite surface could trigger the thermo-responsive connection of the preformed laponite network.

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Radiopaque and biodegradable beads fabricated with Lipiodol and polycaprolactone for transarterial chemoembolization

Okamoto Y., Bito K., Hasebe T., Matsumoto T., Hotta A.

MRS Advances （MRS Advances） 4 （ 20 ） 1187 - 1192 2019年

Copyright © Materials Research Society 2019. Embolic beads for transarterial chemoembolization (TACE) should possess radiopacity and biodegradability at the same time, to be visualized in a body under fluoroscopy and CT scanning to avoid complicating disease. In this study, we fabricated radiopaque and biodegradable beads composed of Lipiodol (LPD) (ethiodized oil) and polycaprolactone (PCL), a biocompatible and biodegradable polymer. LPD/PCL beads were first fabricated with a home-made microfluidic device. By changing the flow-rate ratio in the microfluidic device, the mean diameter of LPD/PCL beads could be well controlled. The radiopacity was evaluated by the fluoroscopic imaging and the CT number measurements. Furthermore, the biodegradability was evaluated by collecting the weight loss data of LPD/PCL immersed in lipase/PBS solution and PBS. The results showed that LPD/PCL beads obtained in this study had sufficient radiopacity and biodegradability, which would be an alternative embolic agent for TACE.

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Enhancement of the mechanical property of poly(ϵ-caprolactone) composites with surface-modified cellulose nanofibers fabricated via electrospinning

Ichimura H., Kurokawa N., Hotta A.

MRS Advances （MRS Advances） 4 （ 7 ） 385 - 391 2019年

Copyright © Materials Research Society 2019. Poly(ϵ-caprolactone) (PCL) is one of the leading biocompatible and biodegradable polymers. However, the mechanical property of PCL is relatively poor as compared with that of polyolefins, which has limited the active applications of PCL as an industrial material. In this study, to enhance the mechanical property of PCL, cellulose nanofibers (C-NF) with high mechanical property, were employed as reinforcement materials for PCL. The C-NF were fabricated via the electrospinning of cellulose acetate (CA) followed by the subsequent saponification of the CA nanofibers. For the enhancement of the mechanical property of the PCL composite, the compatibility of C-NF and PCL was investigated: the surface modification of the C-NF was introduced by the ring-opening polymerization of the ϵ-caprolactone on the C-NF surface (C-NF-g-PCL). The polymerization was confirmed by the Fourier transform infrared (FTIR) spectroscopy. Tensile testing was performed to examine the mechanical properties of the C-NF/PCL and the C-NF-g-PCL/PCL. At the fiber concentration of 10 wt%, the Young's modulus of PCL compounded with neat C-NF increased by 85% as compared with that of pure PCL, while, compounded with C-NF-g-PCL, the increase was 114%. The fracture surface of the composites was analyzed by scanning electron microscopy (SEM). From the SEM images, it was confirmed that the interfacial compatibility between PCL and C-NF was improved by the surface modification. The results demonstrated that the effective surface modification of C-NF contributed to the enhancement of the mechanical property of PCL.

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Annealing and saponification of electrospun cellulose-acetate nanofibers used as reinforcement materials for composites

Inukai S., Kurokawa N., Hotta A.

Composites Part A: Applied Science and Manufacturing （Composites Part A: Applied Science and Manufacturing） 113 158 - 165 2018年10月

ISSN 1359835X

© 2018 Elsevier Ltd To enhance the mechanical properties of regenerated cellulose nanofibers (RC-NF), the annealing and the saponification of electrospun cellulose-acetate nanofibers (CA-NF) have been investigated. It was found that, by increasing the annealing time of CA-NF at 50 °C from 0 to 12 h, the crystallinity of RC-NF increased from 37% to 41%, which became constant after 12 h. By applying the theory proposed by Tsai, the Young's modulus of RC-NF was found to increase from 9.0 to 28.0 GPa by increasing the annealing time from 0 to 12 h, which also became constant after 12 h. The optimized annealing time for the maximum crystallinity and Young's modulus became shorter by increasing the annealing temperature, indicating that the crystallinity and the Young's modulus of RC-NF were strongly correlated. Eventually, the Young's modulus of RC-NF/PVA increased from 2.1 to 3.0 GPa at the maximum, while that of pure PVA was 1.5 GPa.

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Thermomechanical properties of highly transparent self-reinforced polylactide composites with electrospun stereocomplex polylactide nanofibers

Kurokawa N., Hotta A.

Polymer （Polymer） 153 214 - 222 2018年09月

ISSN 00323861

© 2018 Elsevier Ltd Stereocomplex polylactide (sc-PLA) nanofibers with the average diameter of 367 nm were prepared by the conductivity-controlled electrospinning using 7 wt% PLA solution in the mixed solvents of dichloromethane and pyridine. The sc-PLA nanofibers were used as reinforcement materials for poly(L-lactide) (PLLA) to fabricate a self-reinforced PLA composite, while the fibers were compounded into the PLLA by compression molding. Thermomechanical and optical properties of the resulting self-reinforced PLA composites were investigated. It was found that highly transparent (above 75%) self-reinforced PLA composites were obtained up to the sc-PLA fiber concentration of 15 wt%. Also, at higher temperature in the rubbery state, the storage moduli of the composites increased by adding sc-PLA nanofibers. At the fiber concentration of 15 wt%, the storage modulus of the composite became 70 MPa, which was 24.1 times higher than that of the original pure PLLA. It was therefore concluded that the self-reinforced PLA composite with high transparency and high thermomechanical properties was successfully obtained.

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Uniformly dispersed polymeric nanofiber composites by electrospinning: Poly(vinyl alcohol) nanofibers/polydimethylsiloxane composites

Watanabe K., Maeda T., Hotta A.

Composites Science and Technology （Composites Science and Technology） 165 18 - 23 2018年09月

ISSN 02663538

© 2018 Elsevier Ltd A method for the fabrication of homogeneous and well-dispersed polymeric nanofiber composites was investigated. Nanofiber fillers can be used to produce polymeric nanocomposites by mixing the fillers to base polymers, eventually enhancing the mechanical property of the matrix polymers. To produce such composites, nanofibers were usually sandwiched by molten matrix polymers at high temperature before molding. The traditional so-called sandwich method, however, was found to produce rather biased and inhomogeneous composites due largely to the solid entanglement of the nanofibers. In this work, unwoven polymer nanofibers were synthesized through electrospinning by controlling the electrostatic repulsion of the nanofibers. We modified the electrospinning apparatus for the direct synthesis of homogenous composites: nanofibers were electrospun and directly ejected from the electrospinning syringe to the matrix polymer solution (not in a solid state), where a regular metal electrode plate was replaced by an optimized metal container containing the base polymer solution. It was found that this new fabrication method could realize homogeneous mixing of the nanofibers that were eventually uniformly dispersed in the polymer solution. Poly(vinyl alcohol) (PVA) was used for nanofibers and polydimethylsiloxane (PDMS) was used for polymer matrix. The field emission scanning electron microscopy (FE-SEM) revealed the homogeneous and well-dispersed PVA nanofibers in the resulting PDMS composites. The composites also presented higher mechanical properties as compared with the composites fabricated by the traditional sandwich method.

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Mechanically Tough Syndiotactic Polypropylene (sPP) Gels Realized by Fast Quenching Using Liquid Nitrogen

F. Endo, R. Okoshi, K. Takaesu, N. Kurokawa, H. Iwase, T. Maeda, A. Hotta

Macromolecules （ACS Publications） 51 2321 - 2327 2018年02月

研究論文（学術雑誌）, 共著, 査読有り

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Impact of hot wire and material gas species on the Cat-CVD coating of gas barrier SiOC thin films onto PET bottles

M. Nakaya, S. Yasuhara, T. Maeda, A. Hotta

Surface and Coatings Technology （Elsevier） 344 21 - 29 2018年02月

研究論文（学術雑誌）, 共著, 査読有り

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Thermophysical property measurements of tetrabutylphosphonium acetate (TBPAce) ionic semiclathrate hydrate as thermal energy storage medium for general air conditioning systems

Y. Arai, Y. Yamauchi, H. Tokutomi, F. Endo, A. Hotta, S. Alavi, R, Ohmura

International Journal of Refrigeration （Elsevier） 88 102 - 107 2018年01月

研究論文（学術雑誌）, 共著, 査読有り

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Nanocomposite injectable gels capable of self-replenishing regenerative extracellular microenvironments for in vivo tissue engineering

K. Nagahama, N. Oyama, K. Ono, A. Hotta, K. Kawauchi, T. Nishikata

Biomaterials Science （Royal Society of Chemistry） 6 550 - 561 2018年01月

研究論文（学術雑誌）, 共著, 査読有り

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Self-assembly of peptide amphiphiles by vapor pressure osmometry and dissipative particle dynamics

Seki T., Arai N., Suh D., Ozawa T., Shimada T., Yasuoka K., Hotta A.

RSC Advances （RSC Advances） 8 （ 47 ） 26461 - 26468 2018年

© The Royal Society of Chemistry. Peptide amphiphiles are one of the most promising materials in the biomedical field, so much effort has been devoted to characterizing the mechanism of their self-assembly and thermosensitive gelation. In this work, vapor pressure osmometry measurements were carried out to parameterize the thermosensitivity of interactions between peptide amphiphiles in an aqueous solution. The osmometry measurement verified that the peptides became more hydrophobic as temperature increased, which was quantitatively described with the Flory-Huggins χ parameter. Thereafter, a coarse-grained molecular model was used to simulate peptide amphiphiles dissolved in an aqueous solution. The temperature sensitive coarse-grained parameter aHW, which is the repulsive force between the hydrophilic head of the peptide amphiphile and water was estimated from the aforementioned experimentally obtained χ. Furthermore, the effects of concentration and temperature on the self-assembly behavior of peptide amphiphiles were quantitatively studied by dissipative particle dynamics. The simulation results revealed that aHW plays an important role in self-assembly characteristics and in the resulting microstructure of the peptide amphiphiles, which coincides with previous experimental and computational findings. The methodology in quantitatively linking the coarse-grained parameter from experiment and theory provides a sensible foundation for bridging future simulation studies with experimental work on macromolecules.

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PEG-based nanocomposite hydrogel: Thermo-responsive sol-gel transition and degradation behavior controlled by the LA/GA ratio of PLGA-PEG-PLGA

M. Kitagawa, T. Maeda, A. Hotta

Polymer Degradation and Stability （Elsevier） 147 222 - 228 2017年12月

研究論文（学術雑誌）, 共著, 査読有り

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Thermal effects on the strain-induced β to α form crystalline structural transition observed in solid-state syndiotactic polystyrene

F. Endo, A. Hotta

Polymer （Elsevier） 135 （ 17 ） 103 - 110 2017年12月

研究論文（学術雑誌）, 共著, 査読有り

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Gas and flavor barrier thin film coating to plastic closures

M. Nakaya, K. Motomura, T. Maeda, A. Hotta

Quarterly Physics Review （KEI Journals） 4 （ 1 ） 1590 2017年12月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 2572-701X

Thermodynamic Properties of Ionic Semiclathlate Hydrate Formed with Tetrabutylammonium Propionate

Y. Yamauchi, T. Yamasaki, F. Endo, A. Hotta, R. Ohmura

Chemical Engineering & Technology （Wiley） 40 （ 10 ） 1810 - 1816 2017年08月

研究論文（学術雑誌）, 共著, 査読有り

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In vitro basic fibroblast growth factor (bFGF) delivery using micro-patterning of hydrogenated amorphous carbon (a-C:H) film and anti-thrombogenic 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer for stent coating

K. Bito, T. Hasebe, T. Maeda, S. Maegawa, T. Matsumoto, T. Suzuki, A. Hotta

Journal of Biomedical Materials Research Part A （Wiley） 105 （ 12 ） 3384 - 3391 2017年08月

研究論文（学術雑誌）, 共著, 査読有り

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Biocompatibility Tests and Adhesion Improvements for Hydrogen-Free Amorphous Carbon for Blood-Contacting Medical Devices

Y. Yamato, T. Hasebe, S. Maegawa, K. Bito, T. Matsumoto, T. Mine, T. Hayashi, A. Hotta, T. Suzuki

Sensors and Materials （MYU K.K.） 29 （ 6 ） 843 - 854 2017年06月

研究論文（学術雑誌）, 共著, 査読有り

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Composition-dependent sol-gel transition of amphiphilic blend of PEG with hydrophobic gallamide components

A. Aso, K. Taki, T. Maeda, K. Toma, H. Tamiaki, A. Hotta

Journal of Applied Polymer Science （Wiley） 135 （ 24 ） 45402 2017年06月

研究論文（学術雑誌）, 共著, 査読有り

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Mechanical properties of poly(butylene succinate) composites with aligned cellulose-acetate nanofibers

N. Kurokawa, S. Kimura, A. Hotta

Journal of Applied Polymer Science （Wiley） 135 （ 24 ） 45429 2017年06月

研究論文（学術雑誌）, 共著, 査読有り

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Thermoplastic polydimethylsiloxane with L-phenylalanine based hydrogen-hond networks

S. Tazawa, A. Shimojima, T. Maeda, A. Hotta

Journal of Applied Polymer Science （Wiley） 135 （ 24 ） 45419 2017年06月

研究論文（学術雑誌）, 共著, 査読有り

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PEG-based nanocomposite hydrogel: Thermoresponsive sol-gel transition controlled by PLGA-PEG-PLGA molecular weight and solute concentration

M. Miyazaki, T. Maeda, K. Hirashima, N. Kurokawa, K. Nagahama, A. Hotta

Polymer （Elsevier） 115 246 - 254 2017年03月

研究論文（学術雑誌）, 共著, 査読有り

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Phase equilibrium temperature and dissociation heat of ionic semiclathrate hydrate formed with tetrabutylammonium butyrate

Y. Yamauchi, Y. Arai, T. Yamasaki, F. Endo, A. Hotta, R. Ohmura

Fluid Phase Equilibria （Elsevier） 441 （ 15 ） 54 - 58 2017年02月

研究論文（学術雑誌）, 共著, 査読有り

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Time course analysis of antithrombogenic properties of fluorinated diamond-like carbon coating determined via accelerated aging tests: Quality control for medical device commercialization

S. Maegawa, T. Hasebe, Y. Yamato, K. Bito, S. Nagashima, T. Hayashi, T. Mine, T. Matsumoto, A. Hotta, T. Suzuki

Diamond and Related Materials （Elsevier） 70 33 - 38 2016年11月

研究論文（学術雑誌）, 共著, 査読有り

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Recent Progress in Gas Barrier Thin Film Coatings on PET Bottles in Food and Beverage Applications

M. Nakaya, A. Uedono, A. Hotta

Coatings （MDPI） 5 987 - 1001 2015年11月

研究論文（学術雑誌）, 共著, 査読有り

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Syndiotactic polypropylene nanofibers obtained from solution electrospinning process at ambient temperature

T. Maeda, K. Takaesu, and A. Hotta

Journal of Applied Polymer Science （Wiley） 133 43238 2015年10月

研究論文（学術雑誌）, 共著, 査読有り

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Enhancement of the gas barrier property of polypropylene by introducing plasma-treated silane coating with SiOx-modified top-surface

K. Tsuji, M. Nakaya, A. Uedono, A. Hotta

Surface and Coating Technology （Elsevier） 284 377 - 383 2015年08月

研究論文（学術雑誌）, 共著, 査読有り

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Biodegradability, reprocessability, and mechanical properties of polybutylene succinate (PBS) photografted by hydrophilic or hydrophobic membranes

S. Mizuno, T. Maeda, C. Kanemura, and A. Hotta

Polymer Degradation and Stability （Elsevier） 117 58 - 65 2015年03月

研究論文（学術雑誌）, 共著, 査読有り

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Poly(2-methacryloyloxyethyl phosphorylcholine) (MPC) nanofibers coated with micro-patterned diamond-like carbon (DLC) for the controlled drug release

K. Bito, T. Maeda, K. Hagiwara, S. Yoshida, T. Hasebe, A. Hotta

Journal of Biorheology （J-STAGE） 29 51 - 55 2015年02月

研究論文（学術雑誌）, 共著, 査読有り

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Structural and mechanical properties of cellulose composites made of isolated cellulose nanofiber and poly(vinyl alcohol)

Y. Oishi, M. Nakaya, E. Matsui, A. Hotta

Composites Part A （Elsevier） 73 72 - 79 2015年02月

研究論文（学術雑誌）, 共著, 査読有り

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Electrospray formation of ring-shaped silica nanoparticles

K. Uchida, K. Higashi, K. Hishida, A. Hotta, N. Miki

Japanese Journal of Applied Physics （IOP Publishing Ltd） 54 020302 2015年02月

研究論文（学術雑誌）, 共著, 査読有り

Effects of Salt Concentrations of the Aqueous Peptide-Amphiphile Solutions on the Sol-Gel Transitions, the Gelation Speed, and the Gel Characteristics

T. Otsuka, T. Maeda, A. Hotta

The Journal of Physical Chemistry　Part B （American Chemical Society） 118 （ 39 ） 11537 - 11545 2014年09月

研究論文（学術雑誌）, 共著, 査読有り

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A nanocomposite approach to develop biodegradable thermogels exhibiting excellent cell-compatibility for injectable cell delivery

N. Oyama, H. Minami, D. Kawano, M. Miyazaki, T. Maeda, K. Toma, A. Hotta, K. Nagahama

Biomaterials Science （Royal Society of Chemistry） 2 （ 8 ） 1057 - 1062 2014年06月

研究論文（学術雑誌）, 共著, 査読有り

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Preparation and characterization of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer nanofibers prepared via electrospinning for biomedical materials

T. Maeda, K. Hagiwara, S. Yoshida, T. Hasebe, A. Hotta

Journal of Applied Polymer Science （Wiley） 131 40606 2014年02月

研究論文（学術雑誌）, 共著, 査読有り

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The Structure and the Mechanical Properties of a Newly Fabricated Cellulose-Nanofiber/Polyvinyl-Alcohol Composite

Y. Oishi, A. Hotta

Mater. Res. Soc. Symp. Proc. （Cambridge Journals） 1621 mrsf13-1621-c06-12 2014年01月

研究論文（学術雑誌）, 共著, 査読有り

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Effects of Salt Concentrations on the Structural Transitions of Peptide-Amphiphile Solution

T. Otsuka, A. Hotta

Mater. Res. Soc. Symp. Proc. （Cambridge Journals） 1622 mrsf13-1622-e11-02 2014年01月

研究論文（学術雑誌）, 共著, 査読有り

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Basic fibroblast growth factor as a potential stent coating material inducing endothelial cell proliferation

N. Kitamura, T. Hasebe, T. Matsumoto, A. Hotta, T. Suzuki, T. Yamagami, H Terada

Journal of Atherosclerosis and Thrombosis （Japan Atherosclerosis Society） 21 （ 5 ） 477 - 485 2013年12月

研究論文（学術雑誌）, 共著, 査読有り

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Hydrophobicity and non-thrombogenicity of nanoscale dual rough surface coated with fluorine-incorporated diamond-like carbon films: Biomimetic surface for blood-contacting medical devices

Terumitsu Hasebe, So Nagashima, Aki Kamijo, Myoung-Woon Moon, Yousuke Kashiwagi, Atsushi Hotta, Kwang-Ryeol Lee, Koki Takahashi, Takuji Yamagami, Tetsuya Suzuki

Diamond and Related Materials （Elsevier） 38 14-18 2013年06月

研究論文（学術雑誌）, 共著, 査読有り

Micropatterning of Silica Nanoparticles by Electrospray Deposition through a Stencil Mask

K. Higashi, K. Uchida, K. Hishida, A. Hotta, N. Miki.

Journal of Laboratory Automation （the Society for Laboratory Automation and Screening） 19 75 - 81 2013年06月

研究論文（学術雑誌）, 共著, 査読有り

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Hydrophobicity and non-thrombogenicity of nanoscale dual rough surface coated with fluorine-incorporated diamond-like carbon films: Biomimetic surface for blood-contacting medical devices

T. Hasebe, S. Nagashima, A. Kamijo, MW. Moon, Y. Kashiwagi, A. Hotta, KR. Lee, K. Takahashi, T. Yamagami, T. Suzuki

Diamond and Related Materials （Elsevier） 38 14 - 18 2013年06月

研究論文（学術雑誌）, 共著, 査読有り

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Syndiotactic polypropylene nanofibers fabricated by a solution electrospinning method with single solvent at ambient temperature

T. Maeda, K. Takaesu, A. Hotta

Polymeric Materials: Science & Engineering （American Chemical Society） 245 402 2013年04月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Controlling the biodegradability of poly(butylene succinate) by photoinduced graft polymerization

T. Maeda, C. Kanemura, A. Hotta

Polymeric Materials: Science & Engineering （American Chemical Society） 245 199 2013年04月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Enhancement of the gas barrier property of polymers by DLC coating with organosilane interlayer

H. Tashiro, M. Nakaya, A. Hotta

Diamond and Related Materials （Elsevier） 35 7-23 2013年03月

研究論文（学術雑誌）, 共著, 査読有り

Surface modification of polymers by plasma treatments for the enhancement of biocompatibility and controlled drug release

S. Yoshida, K. Hagiwara, T. Hasebe, A. Hotta

Surface and Coating Technology （Elsevier） 233 99 - 107 2013年03月

研究論文（学術雑誌）, 共著, 査読有り

Manufacture of glass nanoparticles by electrospraying

K. Uchida, A. Hotta, K. Hishida, N. Miki

Journal of Micromechanics and Microengineering （Institute of Physics） 23 025023 2013年02月

研究論文（学術雑誌）, 共著, 査読有り

Improvement of Gas Barrier Property of Polyolefins by Diamond-Like Carbon Deposition and Photografting Polymerization

J. Takahashi, M. Nakaya, E. Matsui, A. Hotta

Journal of Applied Polymer Science （Wiley） 129 2591-2597 2013年01月

研究論文（学術雑誌）, 共著, 査読有り

Ultrastructural Characterization of Surface-Induced Platelet Activation on Artificial Materials by Transmission Electron Microscopy

Y. Yoshimoto, T. Hasebe, K. Takahashi, M. Amari, S. Nagashima, A.Kamijo, A.Hotta, K. Takahashi, T. Suzuki

Microscopy Research and Technique （Wiley） 76 342-349 2013年01月

研究論文（学術雑誌）, 共著, 査読有り

Anti-bacterial property of hydrogen-free amorphous carbon coatings on Ar plasma-pretreated polytetrafluoroethylene (PTFE) with a-C:H:F interlayer

H. Umemoto, T. Hasebe, R. Kasai, Y. Yoshimoto, S. Nagashima, A. Hotta, T. Suzuki

Mater. Res. Soc. Symp. Proc. （MRS） 1505 opl.2013.526 2012年11月

研究論文（学術雑誌）, 共著, 査読有り

Effects of plasma treatments on the controlled drug release from poly(ethylene-co-vinyl acetate)

K. Hagiwara, T. Hasebe, A. Hotta

Surface and Coatings Technology （Elsevier） 216 318-323 2012年11月

研究論文（学術雑誌）, 共著, 査読有り

Human Umbilical Vein Endothelial Cell Interaction with Fluorine-Incorporated Amorphous Carbon Films

Y. Yoshimoto, T. Hasebe, S. Nagashima, A. Kamijo, T.Nakatani, T. Yamagami, N. Kitamura, T. Kitagawa, A. Hotta, K. Takahashi, T. Suzuki

Japanese Journal of Applied Physics （Tha Japan Society of Applied Physics） 51 090129 2012年08月

研究論文（学術雑誌）, 共著, 査読有り

Solution parameters for the fabrication of thinner silicone fibers by electrospinning

A. Nakano, N. Miki, K. Hishida, A. Hotta

Physical Review E （American Physical Society） 86 011801 2012年07月

研究論文（学術雑誌）, 共著, 査読有り

Adhesion enhancement of polyolefins by diamond like carbon coating and photografting polymerization

J. Takahashi, A. Hotta

Diamond and Related Materials （Elsevier） 26 55-59 2012年06月

研究論文（学術雑誌）, 共著, 査読有り

Laminin active peptide/agarose matrices as multifunctional biomaterials for tissue engineering

Y. Yamada, K. Hozumi, A. Aso, A. Hotta, K. Toma, F. Katagiri, Y. Kikkawa, M. Nomizu

Biomaterials （Elsevier） 33 4118-4125 2012年06月

研究論文（学術雑誌）, 共著, 査読有り

Mechanical properties and chemical structures of biodegradable poly(butylene-succinate) for material reprocessing

C. Kanemura, S. Nakashima, A. Hotta

Polymer Degradation and Stability （Elsevier） 97 972-980 2012年06月

研究論文（学術雑誌）, 共著, 査読有り

Controlled formation of wrinkled diamond-like carbon (DLC) film on grooved poly(dimethylsiloxane) substrate

S. Nagashima, T. Hasebe, D. Tsuya, T. Horikoshi, M. Ochiai, S. Tanigawa, Y. Koide, A. Hotta, T. Suzuki

Diamond and Related Materials （Elsevier） 22 48-51 2012年02月

研究論文（学術雑誌）, 共著, 査読有り

Gas permeability and mechanical properties of PDMS mixed with PMPS nanofibers produced by electrospinning

A. Nakano, N. Miki, A. Hotta

Mater. Res. Soc. Symp. Proc. （Materiasl Research Society） 1410 opl.2012.663 2011年11月

研究論文（学術雑誌）, 共著, 査読有り

石器の使用痕形成におよぼす材料特性の影

米倉薫 , 堀田篤 , 鈴木哲也

第四紀研究（日本第四紀学会） 50 （ 4 ） 195-204 2011年08月

研究論文（学術雑誌）, 共著, 査読有り

Tailoring surface topographies of polymers by using ion beam: Recent advances and the potential applications in biomedical and tissue engineering

T. Hasebe, S. Nagashima, Y. Yoshimoto, A. Hotta, T. Suzuki

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms （Elsevier） 282 134-136 2011年07月

研究論文（学術雑誌）, 共著, 査読有り

Fluid Mechanical Shear Induces Structural Transitions in Assembly of a Peptide-Lipid Conjugate

T. Shimada, K.Megley, M. Tirrell, A. Hotta

Soft Matter （RSC (Royal Society of Chemistry) publishing） 7 8856-8861 2011年07月

研究論文（学術雑誌）, 共著, 査読有り

Stress-strain behavior, elastic recovery, fracture points, and time-temperature superposition of an OOT-possessing triblock copolymer

Y. Orimo, A.Hotta

Macromolecules （American Chemical Society） 44 （ 13 ） 5310-5317 2011年06月

研究論文（学術雑誌）, 共著, 査読有り

Design for improved adhesion of fluorine-incorporated hydrogenated amorphous carbon on metallic stent: three-layered structure with controlled surface free energy

T. Hasebe, K. Murakami, S. Nagashima, Y. Yoshimoto, A. Ihara, M.Otake, R. Kasai, S. Kasuya, N. Kitamura, A. Kamijo, H. Terada, A. Hotta, K.Takahashi, T. Suzuki

Diamond and Related Materials （Elsevier） 20 （ 7 ） 902-906 2011年05月

研究論文（学術雑誌）, 共著, 査読有り

Adhesion of amorpous carbon deposited polyolefin materials by the plasma enhanced CVD method

J. Takahashi, Y. Nakamura, A. Hotta

Polymer Preprints （American Chemical Society） 241 35 - 36 2011年03月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Combining polymers with diamond-like carbon (DLC) for highly functionalized materials

R. Asakawa, S. Nagashima, Y. Nakamura, T. Hasebe, T. Suzuki, A. Hotta

Surface and Coatings Technology （Elsevier） 206 （ 4 ） 676-685 2011年03月

研究論文（学術雑誌）, 共著, 査読有り

beta to alpha form transition observed in the crystalline structures of syndiotactic polystyrene (sPS)

T. Ouchi, S. Nagasaka, A. Hotta

Macromolecules （American Chemical Society） 44 （ 7 ） 2112-2119 2011年03月

研究論文（学術雑誌）, 共著, 査読有り

Influence of stereoregularity on heat contraction behavior of polypropylene

M. Akiyama, A. Hotta

Polymeric Materials: Science & Engineering （ACS (American Chemical Society)） 241 406 - 408 2011年03月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Crystalline orientation after heat contraction observed in elongated polypropyelenes

M. Akiyama, A. Hotta

Polymeric Materials: Science & Engineering （American Chemical Society） 241 33 2011年03月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

beta to alpha crystalline phase transition of syndiotactic polystyrene (sPS) induced by mechanical strain

T. Ouchi, S. Nagasaka, A. Hotta

Polymer Preprints （ACS） 241 2011年03月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Thermal and mechanical properties of polypropylene gels and homo polypropylenes

T. Ouchi, M. Yamazaki, A. Hotta

Polymeric Materials: Science & Engineering （American Chemical Society） 241 219 - 220 2011年03月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Adhesion enhancement of polyolefins by chemical vapor deposition and photografting polymerization

J. Takahashi, A. Hotta

Polymeric Materials: Science & Engineering （American Chemical Society） 241 335 2011年03月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

炭素系素材の将来展望—2050年に向けて−DLC薄膜を用いた新世代医療器具の開発

長谷部光泉，吉本幸洋，永島壮，上條亜紀，堀田篤，髙橋孝喜，鈴木哲也

New Diamond （ニューダイヤモンドフォーラム） 27 （ 1 ） 66-78 2011年01月

研究論文（学術雑誌）, 共著, 査読有り

Characterization of a bonding-in-liquid technique for liquid encapsulation into MEMS devices

Y. Okayama, K. Nakahara, X. Arouette, T. Ninomiya, Y. Matsumoto, Y. Orimo, A. Hotta, M. Omiya, N.Miki

Journal of Micromechanics and Microengineering （IOP (Institute Of Physics)） 20 095018 2010年08月

研究論文（学術雑誌）, 共著, 査読有り

Processing-Structure-Mechanical Property Relationships of Semicrystalline Polyolefin-Based Block Copolymers

F. Deplace, ZG. Wang, NA. Lynd, A. Hotta,JM. Rose, PD. Hustad,J. Tian, H. Ohtaki, GW. Coates, F. Shimizu, K. Hirokane, F. Yamada, YW. Shin, LX. Rong, J. Zhu, S. Toki, BS. Hsiao, GH. Fredrickson, EJ. Kramer

Journal of Polymer Science Part-B Polymer Physics （Wiley） 48 1428-1437 2010年07月

研究論文（学術雑誌）, 共著, 査読有り

Controlling the drug release rate from biocompatible polymers with micropatterned　Diamond-Like Carbon (DLC) coating

K. Enomoto, T. Hasebe, R. Asakawa, A. Kamijo, Y. Yoshimoto, T. Suzuki, K. Takahashi, A. Hotta

Diamond and Related Materials （Elsevier） 19 806-813 2010年07月

研究論文（学術雑誌）, 共著, 査読有り

Effect of Oxygen Plasma Treatment on Non-thrombogenicity of Diamond-like Carbon Films

S. Nagashima, T. Hasebe,A. Kamijo, Y. Yoshimoto,A. Hotta, H. Morita, H. Terada, M. Tanaka, K. Takahashi, T. Suzuki

Diamond and Related Materials （Elsevier） 19 861-865 2010年07月

研究論文（学術雑誌）, 共著, 査読有り

Supramolecular gelation of alcohol and water by synthetic amphiphilic gallic acid derivatives

H. Tamiaki, K. Ogawa, K. Enomoto, K. Taki, A. Hotta, K. Toma

Tetrahedron （Elsevier） 66 1661-1666 2010年01月

研究論文（学術雑誌）, 共著, 査読有り

Wormlike Micelle Formation in Peptide-Lipid Conjugates Driven by Secondary Structure Transformation of the Headgroups

T. Shimada, S. Lee, F.S. Bates, A. Hotta, M. Tirrell

The Journal of Physical Chemistry B （ACS） 113 13711-13714 2009年07月

研究論文（学術雑誌）, 共著, 査読有り

Dissipative Particle Dynamics Studies on the Self-Assembling Dynamics of the Peptide Amphiphiles

T. Seki, N. Arai, T. Ozawa, T. Shimada, K. Yasuoka and A. Hotta

Mater. Res. Soc. Symp. Proc. （MRS (Materials Research Society)） 1135E 1135-CC06-02 2009年06月

研究論文（学術雑誌）, 共著, 査読有り

ダイヤモンドライクカーボン膜を被覆したメディカルデバイスの開発

長谷部光泉、吉本幸洋、上條亜紀、堀田篤、児玉英之、田中実、石川治、今野謙次郎、北村範子、寺田一志、斉藤延人、高橋孝喜、鈴木哲也

工業材料 57 （ 6 ） 42 - 47 2009年06月

研究論文（学術雑誌）, 共著, 査読有り

DLC薄膜とポリマー複合化材料を用いた薬剤溶出システムの研究

長谷部光泉、浅川玲奈、榎本圭佑、上條亜紀、鈴木哲也、堀田篤

New Diamond 25 （ 2 ） 26-28 2009年04月

研究論文（学術雑誌）, 共著, 査読有り

Effects of bilayer thickness and post-deposition annealing on the mechanical and structural properties of (Ti, Cr, Al)N/(Al, Si)N multilayer coatings

N. Fukumoto, H. Ezura, K. Yamamoto, A. Hotta, T. Suzuki

Surface and Coatings Technology （Elsevier） 203 （ 10 ） 1343-1348 2009年02月

研究論文（学術雑誌）, 単著

Structural, Thermal and Rheological Studies on Newly Developed Polyesters Randomly Copolymerized with Poly(tetramethylene glycol) (PTMG)

O. Matsumoto, A. Hotta

Mater. Res. Soc. Symp. Proc. （Materials Research Society） 1151E 1151-SS01-04 2009年01月

研究論文（学術雑誌）, 共著, 査読有り

C-2-Symmetric Ni(II) alpha-Diimines Featuring Cumyl-Derived Ligands: Synthesis of Improved Elastomeric Regioblock Polypropylenes

JM. Rose, F. Deplace, NA. Lynd, ZG. Wang, A. Hotta, EB. Lobkovsky, EJ. Kramer, GW. Coates

Macromolecules （ACS (American Chemical Society)） 41 （ 24 ） 9548-9555 2008年12月

研究論文（学術雑誌）, 共著, 査読有り

Investigation of heterostructure between diamond and iridium on sapphire

A. Samoto, S. Ito, A. Hotta, T. Hasebe, Y. Ando, A. Sawabe, T. Suzuki

Diamond and Related Materials （Elsevier） 17 （ 7-10 ） 1039-1044 2008年10月

研究論文（学術雑誌）, 共著, 査読有り

A Novel Approach to Studies of Prehistoric Exploitation of Stone Tool Materials Using Material Composition, Surface Morphology, Microstructure and Mechanical Properties

K. Yonekura, H. Hasegawa, A. Hotta, T.Suzuki

Archaeometry （Wiley） 50 727-746 2008年08月

研究論文（学術雑誌）, 共著, 査読有り

Micro-hardness, microstructures and thermal stability of (Ti,Cr,Al,Si)N films deposited by cathodic arc method

H. Ezura, K. Ichijo, H. Hasegawa, K. Yamamoto, A. Hotta, T. Suzuki

Vacuum （Elsevier） 82 （ 5 ） 476-481 2008年01月

研究論文（学術雑誌）, 共著, 査読有り

Recent advances in diamond-like carbon films in the medical and food packing fields

T. Hasebe, A. Hotta, H. Kodama, A. Kamijo, K. Takahashi, T. Suzuki

New Diamond and Frontier Carbon Technology （MYU） 17 （ 6 ） 263 - 279 2007年12月

研究論文（学術雑誌）, 共著, 査読有り

Fluorine doping into diamond-like carbon coatings inhibits protein adsorption and platelet activation

T. Hasebe, S. Yohena, A. Kamijo, Y. Okazaki, A. Hotta, K. Takahashi, T. Suzuki

Journal of Biomedical Materials Research Part A （Wiley） 83A （ 4 ） 1192-1199 2007年12月

研究論文（学術雑誌）, 共著, 査読有り

Depth profiling of fluorine-doped diamond-like carbon (F-DLC) film: Localized fluorine in the top-most thin layer can enhance the non-thrombogenic properties of F-DLC

T. Hasebe, S. Nagashima, A. Kamijo, T. Yoshimura, T. Ishimaru, Y. Yoshimoto, S. Yohena, H. Kodama, A. Hotta, K. Takahashi, T. Suzuki

Thin Solid Films （Elsevier） 516 299-303 2007年12月

研究論文（学術雑誌）, 共著, 査読有り

Controlling the Adhesion between Diamond-like Carbon (DLC) Film and High-Density Polyethylene (HDPE) Substrate

T. Hoshida, D. Tsubone, K. Takada, H. Kodama, T. Hasebe, A. Kamijo, T. Suzuki, A. Hotta

Surface and Coatings Technology （Elsevier） 202 1089-1093 2007年12月

研究論文（学術雑誌）, 共著, 査読有り

Pseudo-tetrablock copolymers with ethylene and a functionalized comonomer

Robert C. Coffin, Steve J. Diamanti, Atsushi Hotta, Vikram Khanna, Edward J. Kramer, Glenn H. Fredrickson and Guillermo C. Bazan

Chemical Communications （RSC (Royal Society of Chemistry)） 34 3550-3552 2007年09月

研究論文（学術雑誌）, 共著, 査読有り

Effect of surface roughness on antithrombogenicity of diamond-like carbon films

T. Hasebe, T. Ishimaru, A. Kamijo, Y. Yoshimoto, T. Yoshimura, S. Yohena, H. Kodama, A. Hotta, K. Takahashi, T. Suzuki

Diamond and Related Materials （Elsevier） 16 1343-1348 2007年01月

研究論文（学術雑誌）, 共著, 査読有り

Fracture Mechanics of Diamond-Like Carbon (DLC) Films Coated on Flexible Polymer Substrates

D. Tsubone, T. Hasebe, A. Kamijo, A. Hotta

Surface and Coatings Technology （Elsevier） 201 6423 - 6430 2007年01月

研究論文（学術雑誌）, 共著, 査読有り

Gas barrier properties and periodically fractured surface of thin DLC films coated on flexible polymer substrates

D. Tsubone, H. Kodama, , T. Hasebe, A. Hotta

Surface and Coatings Technology （Elsevier） 201 6431-6436 2007年01月

研究論文（学術雑誌）, 共著, 査読有り

Properties of Amorphous Carbon Films Synthesized by Atmospheric Pressure Glow Plasma CVD Method

H. Kodama, S. Iizumi, M. Nakaya, A. Shirakura, A. Hotta, T. Suzuki

Journal of photopolymer science and technology （Technical Assoc Photopolymers） 19 673-678 2006年11月

研究論文（学術雑誌）, 共著, 査読有り

生体利用を目指した炭素材料:DLCの医療機器への応用

T. Hasebe, A. Kamijo, A.Hotta, K. Takahashi, T. Suzuki

化学と工業、日本化学会 59 1064-1068 2006年10月

研究論文（学術雑誌）, 共著, 査読有り

Semi-crystalline Thermoplastic Elastomeric Polyolefins: Advances Through Catalyst Development and Macromolecular Design

A. Hotta, E. Cochran, J. Ruokolainen, V. Khanna, GH. Fredrickson, EJ. Kramer, YW. Shin, F. Shimizu, AE. Cherian, JM. Rose, GW. Coates

Proceedings of the National Academy of Sciences of the United States of Amercia (PNAS, 米科学アカデミー紀要) （National Academy of Sciences of the USA） 103 15327-15332 2006年10月

研究論文（学術雑誌）, 共著, 査読有り

Gas Barrier Properties of Carbon Films Synthesized by Atmospheric Pressure Glow Plasma

H. Kodama, A. Shirakura, A. Hotta, T. Suzuki

Surface and Coatings Technology （Elsevier） 201 931-917 2006年09月

研究論文（学術雑誌）, 共著, 査読有り

On the glassy state of multi-phase and pure polymer materials

S. Baeurle, A. Hotta, A. Gusev

Polymer （Elsevier） 17 6243-6253 2006年05月

研究論文（学術雑誌）, 共著, 査読有り

Fibril Formation on an Alanine-Based Peptide Attached to an Alkyl Tail

T. Shimada, A. Hotta, M. Tirrell

Polymeric Materials: Science & Engineering （American Chemical Society） 94 90-91 2006年03月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Tapered block copolymers containing ethylene and a functionalized comonomer

SJ. Diamanti, V. Khanna, A.Hotta, RC. Coffin, D. Yamakawa, EJ. Kramer, GH.Fredrickson, GC. Bazan

Macromolecules （American Chemical Society） 39 3270-3274 2006年02月

研究論文（学術雑誌）, 共著, 査読有り

Synthesis of Practical High-Gas-Barrier Carbon Films at Low and Atmospheric Pressure for PET Bottles

H. Kodama, M. Nakaya, A. Shirakura, A. Hotta, T. Hasebe, T. Suzuki

New Diamond and Frontier Carbon Technology 16 107-119 2006年02月

研究論文（学術雑誌）, 共著, 査読有り

ダイヤモンドライクカーボン薄膜の食品包装および医療機器への応用

児玉英之、中谷正樹、白倉晶、長谷部光泉、堀田篤、鈴木哲也

塗装工学 41 （ 1 ） 14-24 2006年01月

研究論文（学術雑誌）, 共著, 査読有り

Diamond-like carbon and fluorinated diamond-like carbon films for cardiovascular medical devices

長谷部光泉、上條亜紀、堀田篤、高橋孝喜、鈴木哲也

表面技術誌 56 （ 12 ） 897-905 2005年12月

研究論文（学術雑誌）, 共著, 査読有り

ポリマーの自己組織的構造形成

堀田篤

化学工学会ナノプロセシング D317 1-10 2005年09月

研究論文（研究会，シンポジウム資料等）, 単著, 査読有り

Thermal and Mechanical Properties of Gradient Copolymers containing Ethylene and 5-Norbornen-2yl Acetate

A. Hotta, SJ. Diamanti, V. Khanna, GC. Bazan, GH Fredrickson and EJ. Kramer

Polymer Preprints （American Chemical Society） 46 1084-1085 2005年09月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

Synthesis of block copolymers segments containing different ratios of ethylene and 5-norbornen-2-yl acetate

SJ. Diamanti, V. Khanna, A. Hotta, D. Yamakawa, F. Shimizu, EJ. Kramer, G. Fredrickson and GC. Bazan

J. Am. Chem. Soc. 126 10528-10529 2004年10月

研究論文（学術雑誌）, 共著, 査読有り

A new semi-phenomenological approach to predict the stress relaxation behavior of thermoplastic elastomers

S. Baeurle, A. Hotta and A. Gusev

Polymer 46 4344-4354 2004年08月

研究論文（学術雑誌）, 共著, 査読有り

Dynamic soft elasticity in monodomain nematic elasotmers

A. Hotta and E.M. Terentjev

Euro. Phys. J. E 10 291-301 2003年04月

研究論文（学術雑誌）, 共著, 査読有り

Liquid crystalline elastomers: dynamics and relaxation of microstructure

E.M. Terentjev, A. Hotta, S. M. Clarke and M. Warner

Philos. T Roy. Soc. A 361 653-664 2003年02月

研究論文（学術雑誌）, 共著, 査読有り

Effect of Crosslinker Geometry on Dynamic Mechanical Properties of Nematic Elastomers

S.M. Clarke, A. Hotta, A.R. Tajbakhsh and E.M. Terentjev

Phys. Rev. E 65 （ 021804 ） 1-6 2002年01月

研究論文（学術雑誌）, 共著, 査読有り

Long-time Stress Relaxation in Polyacrylate Nematic Liquid Crystalline Elastomers

A. Hotta and E.M. Terentjev

J. Phys. Cond. Mat. 13 11453-11464 2001年11月

研究論文（学術雑誌）, 共著, 査読有り

Effect of Crosslinker Geometry on Equilibrium Thermal and Mechanical Properties of Nematic Elastomers

S.M. Clarke, A. Hotta, A.R. Tajbakhsh and E.M. Terentjev

Phys. Rev. E 64 （ 061702 ） 1-8 2001年11月

研究論文（学術雑誌）, 共著, 査読有り

Stress Relaxation in Transient Networks of Symmetric Triblock SIS Copolymers

A. Hotta, S.M. Clarke and E.M. Terentjev

Macromolecules 35 271-277 2001年09月

研究論文（学術雑誌）, 共著, 査読有り

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