研究者詳細 - 野呂　篤史

論文 - 野呂　篤史

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Effect of Alkyl Side Chain Length on Microscopic Structures and Mechanical Properties of Ionically-Functionalized Block Polymer-Based Thermoplastic Elastomers 査読有り国際誌 Open Access

Suzuki,K.; Kajita,T.; Ota,M.; Nakama, Y.; Tamura, Y.; Kinoshita, S.; Kato,D.; Oda, R.; Hashimoto,S.; Noro, A.

POLYMER CHEMISTRY accepted 巻 2025年4月

Polymer Electrolyte Membranes of Polystyrene with Directly Bonded Alkylenephosphonate Groups on the Side Chains 査読有り Open Access

Nakayama, T; Kajita, T; Nishimoto, M; Tanaka, H; Sato, K; Marium, M; Mufundirwa, A; Iwamoto, H; Noro, A

ACS APPLIED POLYMER MATERIALS 6 巻 ( 24 ) 頁： 15150 - 15161 2024年12月

担当区分：筆頭著者,　責任著者記述言語：英語出版者・発行元：ACS Applied Polymer Materials

There is a pressing need for polymer electrolyte membranes (PEMs) for next-generation polymer electrolyte fuel cells that exhibit good conductivities even at temperatures >100 °C (the boiling point of water) under low humidity. Disadvantages of conventional PEMs made of sulfonic acid polymers generally include low conductivities and easy degradation at temperatures >100 °C under low humidity because of decomposition of the sulfonic acid groups. In this study, diethyl 4-(p-styryl)-1-butanephosphonate and poly(4-(p-styryl)-1-butanephosphonic acid) (sbPA) with phosphonic acid groups on the side chains through a hydrophobic alkylene spacer were synthesized by polymerization of the monomer and deprotection of the phosphonate esters. The sbPA membrane formed a phase-separated structure with a domain spacing of ∼2.5 nm between the hydrophobic part, consisting of phenylene groups and alkylene spacers in the polymer side chains, and the hydrophilic part of the phosphonic acid groups. The sbPA membrane did not dissolve even when immersed in water at 60 °C for 3 h. Despite a lower acid group density than the poly(p-styrenephosphonic acid) (sPA) membrane as a control sample, in which phosphonic acid groups were directly and covalently bonded to the polystyrene backbone, the sbPA membrane exhibited higher conductivities at 80 and 120 °C, especially under low humidity. For example, the sbPA membrane showed a moderate conductivity of 1.1 mS cm-1 at 120 °C and 20% relative humidity, approximately 2 orders of magnitude higher than the conductivity of the sPA membrane. The superior conductivity of the sbPA membrane could be explained by the ease of proton transport between the phosphonic acid groups even under low humidity due to the result of a high freedom of movement made possible by their connection to the polymer backbone directly through the alkylene spacer.

DOI： 10.1021/acsapm.4c02688

Next-Generation Structural Adhesives Composed of Epoxy Resins and Hydrogen-Bonded Styrenic Block Polymer-Based Thermoplastic Elastomers 査読有り Open Access

Yamada, S; Kajita, T; Nishimoto, M; Horiuchi, J; Fujii, Y; Sakaguchi, K; Hattori, K; Tamura, H; Kano, T; Sakai, T; Noro, A

ACS APPLIED MATERIALS & INTERFACES 16 巻 ( 47 ) 頁： 65270 - 65280 2024年9月

担当区分：責任著者記述言語：英語出版者・発行元：ACS Applied Materials and Interfaces

Structural adhesives are currently applied in the assembly of automobiles, aircraft, and buildings. In particular, epoxy adhesives are widely used due to their excellent mechanical strength and durability. However, cured epoxy resins are typically rigid and inflexible; thus, they have low peel and impact strength. In this study, tough cured epoxy adhesives were developed by mixing a liquid epoxy prepolymer (EP) and polystyrene-b-polyisoprene-b-polystyrene (SIS). SIS is a block polymer-based thermoplastic elastomer (TPE) composed of polystyrene (S) soluble in liquid EP and polyisoprene (I) insoluble in liquid EP, where S and I have a glass transition temperature that is higher and lower than room temperature, respectively. In addition, cured adhesives tougher than the cured adhesives containing SIS were prepared by mixing liquid EP and SIS with hydrogen-bonding groups in the I block (h-SIS). Transmission electron microscopy (TEM) observations revealed mixed S/cured EP domains, with a d-spacing of several tens of nanometers, and cured EP domains, with diameters of one hundred to several hundred nanometers, that were macroscopically dispersed in the I or hydrogen-bonded I matrix of the cured adhesive containing SIS or h-SIS. The lap shear, peel, and impact strength of cured neat EP (EP*) were 23 MPa, 45 N/25 mm, and 0.62 kN/m, respectively. Meanwhile, the cured adhesive containing 16.5 wt % SIS exhibited the slightly lower lap shear strength of 17 MPa compared to that of cured EP*, whereas the peel and impact strength of the cured adhesive with SIS were 61 N/25 mm and 7.1 kN/m, respectively, both higher than those of EP*. Furthermore, the lap shear strength of the cured adhesive containing 15.5 wt % h-SIS was 21 MPa, which was similar to that of cured EP*. The cured adhesive with h-SIS also exhibited an excellent peel strength of 97 N/25 mm and an impact strength of 14 kN/m which was 22 times higher than that of cured EP*. Therefore, mixing liquid EP and SIS improved the cured adhesive properties and flexibility of the cured epoxy adhesives compared to the cured adhesive composed of neat EP, and further enhancement of the adhesive properties was achieved by mixing liquid EP and h-SIS with hydrogen-bonding groups instead of mixing with SIS.

DOI： 10.1021/acsami.4c12540

Synthesis of a Cross-Linked Polymer Electrolyte Membrane with an Ultra-High Density of Sulfonic Acid Groups 査読有り Open Access

Sato, K; Kajita, T; Noro, A

ACS APPLIED POLYMER MATERIALS 5 巻 ( 5 ) 頁： 3480 - 3488 2023年4月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Polymer Materials

Sulfonated cross-linked polystyrene membranes, one of the hydrocarbon-based polymer electrolytes membranes (PEMs), are typically synthesized via sulfonation of cross-linked polystyrene. However, it is difficult to prepare a sulfonated cross-linked polystyrene with a high sulfonation level, i.e., a high mole fraction of styrenesulfonic acid unit (fsSA), by using conventional synthetic methods. In this study, to synthesize a relatively homogeneous cross-linked poly(styrenesulfonic acid) (CL-sSA) membrane with an fsSA of 90 mol % or higher, sulfonic acid groups in a styrenesulfonate monomer were protected by esterification, and then a cross-linked polymer was synthesized using the monomer and divinylbenzene. Finally, the cross-linked polymer was converted to CL-sSA by deprotecting the alkyl groups with a base. The conductivity of the CL-sSA membrane at 80 °C and 90% RH was 0.93 S cm-1, which is extremely high and much higher than those of commercially available Nafion 212 and Selemion HSFN membranes with a low fsSA. The synthetic scheme of the CL-sSA membrane used in this study is a very effective route for preparing highly conductive cross-linked PEMs with a high fsSA

DOI： 10.1021/acsapm.3c00150

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85154545161&origin=inward

Effects of a Nanophase-Separated Structure on Mechanical Properties and Proton Conductivity of Acid-Infiltrated Block Polymer Electrolyte Membranes under Non-Humidification 査読有り Open Access

Kajita, T; Tanaka, H; Ohtsuka, Y; Orido, T; Takano, A; Iwamoto, H; Mufundirwa, A; Imai, H; Noro, A

ACS OMEGA 8 巻 ( 1 ) 頁： 1121 - 1130 2023年1月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Omega

Acid-infiltrated block polymer electrolyte membranes adopting a spherical or lamellar nanophase-separated structure were prepared by infiltrating sulfuric acid (H2SO4) into polystyrene-b-poly(4-vinylpyridine)-b-polystyrene (S-P-S) triblock copolymers to investigate the effects of its nanophase-separated structure on mechanical properties and proton conductivities under non-humidification. Lamellae-forming S-P-S/H2SO4 membranes with a continuous hard phase generally exhibited higher tensile strength than sphere-forming S-P-S/H2SO4 membranes with a discontinuous hard phase even if the same amount of Sa was infiltrated into each neat S-P-S film. Meanwhile, the conductivities of lamellae-forming S-P-S/H2SO4 membranes under non-humidification were comparable or superior to those of sphere-forming S-P-S/H2SO4 membranes, even though they were infiltrated by the same weight fraction of H2SO4. This result is attributed to the conductivities of S-P-S/H2SO4 membranes being greatly influenced by the acid/base stoichiometry associated with acid-base complex formation rather than the nanophase-separated structure adopted in the membranes. Namely, there are more free H2SO4 moieties that can release free protons contributing to the conductivity in lamellae-forming S-P-S/H2SO4 membranes than sphere-forming S-P-S/H2SO4, even when the same amount of H2SO4 was infiltrated into the S-P-S.

DOI： 10.1021/acsomega.2c06514

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85144834768&origin=inward

Development of Toughening Technology for Styrenic Thermoplastic Elastomers by Incorporating Non-Covalent Interactions 招待有り Open Access

Oda, R; Noro, A; Kajita, T; Hashimoto, S

NIHON REOROJI GAKKAISHI 51 巻 ( 5 ) 頁： 269 - 272 2023年

担当区分：筆頭著者,　責任著者記述言語：日本語出版者・発行元：Nihon Reoroji Gakkaishi

We have developed schemes for synthesizing polystyrene-b-polyisoprene-b-polystyrene (SIS) with non-covalent bonding groups via the post-polymerization chemical modification that is an industrially-friendly scheme. SIS was first reacted with maleic anhydride in a diluent, followed by reacting with alkylamine. By neutralizing the carboxy group with a metal alkoxide, ionically-modified SIS (i-SIS) was also prepared. i-SIS with a sodium cation (i-SIS(Na)) or a barium cation (i-SIS(Ba)) exhibited excellent tensile toughness of 480 and 230 MJ m–3, respectively. Drop weight impact tests also revealed that i-SIS(Ba) exhibited higher impact resistance than that of typical high-strength glass fiber-reinforced plastic. In the future, by achieving optimization of production of i-SIS in an industrial scale, i-SIS can be used for production of lightweight automobiles, resulting in contribution to achieving net-zero carbon and sustainable society.

DOI： 10.1678/rheology.51.269

Highly Impact-Resistant Block Polymer-Based Thermoplastic Elastomers with an Ionically Functionalized Rubber Phase 査読有り Open Access

Kajita, T; Noro, A; Oda, R; Hashimoto, S

ACS OMEGA 7 巻 ( 3 ) 頁： 2821 - 2830 2022年1月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Omega

There has been a great deal of interest in incorporating noncovalent bonding groups into elastomers to achieve high strength. However, the impact resistance of such elastomers has not been evaluated, even though it is a crucial mechanical property in practical usage, partly because a large-scale synthetic scheme has not been established. By ionizing the rubber component in polystyrene-b-polyisoprene-b-polystyrene (SIS), we prepared several tens of grams of SIS-based elastomers with an ionically functionalized rubber phase and a sodium cation (i-SIS(Na)) or a bulky barium cation (i-SIS(Ba)). The i-SIS(Na) and i-SIS(Ba) exhibited very high tensile toughness of 520 and 280 MJ m-3, respectively. They also exhibited excellent compressive resistance. Moreover, i-SIS(Ba) was demonstrated to have a higher impact resistance, that is, more protective of a material being covered compared to covering by typical high-strength glass fiber-reinforced plastic. As such elastomers can be produced at an industrial scale, they have great market potential as next-generation elastomeric materials.

DOI： 10.1021/acsomega.1c05609

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85122003077&origin=inward

Acidity effects of medium fluids on anhydrous proton conductivity of acid-swollen block polymer electrolyte membranes 査読有り Open Access

Kajita, T; Noro, A; Seki, T; Matsushita, Y; Nakamura, N

RSC ADVANCES 11 巻 ( 31 ) 頁： 19012 - 19020 2021年6月

担当区分：筆頭著者,　責任著者記述言語：英語出版者・発行元：RSC Advances

Proton-conductive polymer electrolyte membranes (PEMs) were prepared by infiltrating sulfuric acid (Sa) or phosphoric acid (Pa) into a polystyrene-b-poly(4-vinylpyridine)-b-polystyrene (S-P-S) triblock copolymer. When the molar ratio of acid to pyridyl groups in S-P-S,i.e., the acid doping level (ADL), is below unity, the P-block/acid phase in the PEMs exhibited a moderately high glass transition temperature (Tg) of ∼140 °C because of consumption of acids for forming the acid-base complexes between the pyridyl groups and the acids, also resulting in almost no free protons in the PEMs; therefore, the PEMs were totally glassy and exhibited almost no anhydrous conductivity. In contrast, when ADL is larger than unity, theTgs of the phase composed of acid and P blocks were lower than room temperature, due to the excessive molar amount of acid serving as a plasticizer. Such swollen PEMs with excessive amounts of acid releasing free protons were soft and exhibited high conductivities even without humidification. In particular, an S-P-S/Sa membrane with ADL of 4.6 exhibited a very high anhydrous conductivity of 1.4 × 10−1S cm−1at 95 °C, which is comparable to that of humidified Nafion membranes. Furthermore, S-P-S/Sa membranes with lowerTgs exhibited higher conductivities than S-P-S/Pa membranes, whereas the temperature dependence of the conductivities for S-P-S/Pa is stronger than that for S-P-S/Sa, suggesting Pa with a lower acidity would not be effectively dissociated into a dihydrogen phosphate anion and a free proton in the PEMs at lower temperatures.

DOI： 10.1039/d1ra01211h

その他リンク： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85106893999&origin=inward

Extremely tough block polymer-based thermoplastic elastomers with strongly associated but dynamically responsive noncovalent cross-links 査読有り

Kajita, T; Tanaka, H; Noro, A; Matsushita, Y; Nozawa, A; Isobe, K; Oda, R; Hashimoto, S

POLYMER 217 巻頁： 123419 2021年3月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymer

To develop elastomers with excellent mechanical properties and processability, block copolymer-based thermoplastic elastomers (TPEs) with dynamic noncovalent cross-links have been actively studied in recent years. Most previous studies on such block copolymer-based TPEs have focused on incorporation of hydrogen-bonded cross-links into the block with a glass transition temperature lower than room temperature; however, the difference between the mechanical properties of hydrogen-bonded TPEs and those of other noncovalent-bonded TPEs has been hardly discussed. This work uses the polystyrene-b-polyisoprene-b-polystyrene (SIS) triblock copolymer produced in industry to synthesize hydrogen-bonded (hSIS) and ionically functionalized thermoplastic elastomers (iSIS) and compares their mechanical properties. iSIS is much tougher than hSIS; remarkably, iSIS exhibits an excellent toughness of 480 MJ m−3, because the ionic multiplets in iSIS serve as much more strongly associated but reversible cross-links. Since the elastomers can be produced at industry scale, they have great market potential for becoming next-generation elastomeric materials.

DOI： 10.1016/j.polymer.2021.123419

DOI： 10.1016/j.polymer.2021.123419

その他リンク： https://doi.org/10.1016/j.polymer.2021.123419

Self-Assembled Hybrids Composed of Block Copolymer/Porphyrin-Metal Complex via Hydrogen Bonding 査読有り

Noro A., Asai H., Higuchi K., Matsushita Y.

ACS Applied Polymer Materials 1 巻 ( 12 ) 頁： 3432 - 3442 2019年12月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Applied Polymer Materials

Macroscopically homogeneous hybrids comprising a block copolymer/porphyrin-metal complex were prepared by mixing a polystyrene-b-poly(4-vinylpyridine) (SP) block copolymer and a porphyrin metal complex with carboxyl groups. The selective and uniform incorporation of a porphyrin metal complex into the poly(4-vinylpyridine) phase of a nanophase-separated structure was achieved by hydrogen bonding between the pyridyl groups of the poly(4-vinylpyridine) block and the carboxyl groups of the porphyrin-metal complex. The phase-separated structures of the hybrids were observed by multiple structural observation tools. The morphology transition depends on the amount of the porphyrin-metal complex added. Furthermore, increasing the amount of added porphyrin-metal complex was found to lead to its precipitation. This result was attributed to a molar amount of pyridyl groups in the poly(4-vinylpyridine) block that was insufficient for hydrogen bonding compared with the amount of carboxyl groups on the porphyrin-metal complex. The precipitation of the porphyrin-metal complex was also affected by the molecular weight of the poly(4-vinylpyridine) block and was observed even when the molar ratio of pyridyl groups to carboxyl groups was larger than unity, suggesting there were still some free pyridyl groups that could be hydrogen-bonded with carboxyl groups. This result could be explained in terms of the effective concentration of the porphyrin-metal complex in solutions during solvent casting.

DOI： 10.1021/acsapm.9b00861

Acidic liquid-swollen polymer membranes exhibiting anhydrous proton conductivity higher than 100 mS cm<SUP>-1</SUP> at around 100 °C 査読有り Open Access

Kajita, T; Tanaka, H; Noro, A; Matsushita, Y; Nakamura, N

JOURNAL OF MATERIALS CHEMISTRY A 7 巻 ( 26 ) 頁： 15585 - 15592 2019年7月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Chemistry A

Anhydrous proton-conductive membranes are prepared by incorporating sulfuric acid (H2SO4) into cross-linked poly(4-vinylpyridine) (CL-P), where H2SO4 mixes CL-P homogeneously at the molecular level, and therefore incorporated H2SO4 does not leach out from CL-P, even when the weight ratio of H2SO4 to CL-P is about four. The membranes are soft but self-standing and exhibit anhydrous conductivity higher than 100 mS cm-1 at around 100 °C. Furthermore, a membrane composed of polystyrene-b-poly(4-vinylpyridine)-b-polystyrene triblock copolymers and H2SO4 achieves not only high anhydrous conductivity but also good mechanical properties as a membrane.

DOI： 10.1039/c9ta01890e

DOI： 10.1039/c9ta01890e

その他リンク： https://pubs.rsc.org/en/content/articlepdf/2019/ta/c9ta01890e

Design and properties of supramolecular elastomers 招待有り査読有り

Kajita, T; Noro, A; Matsushita, Y

POLYMER 128 巻頁： 297 - 310 2017年10月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Polymer

Supramolecular elastomers are supramolecular soft polymeric materials with both transient cross-links and (semi)permanent cross-links, where transient cross-links have a finite relaxation time and are typically composed of noncovalent bonds such as hydrogen bonds, metal–ligand coordination bonds, etc., whereas (semi)permanent cross-links such as covalent bonds, crystalline segments and glassy hard domains have an infinite relaxation time. Excellent elastomeric properties were induced by a combination of all the above molecular features. However, if soft polymeric materials have only supramolecular/transient cross-links with a finite relaxation time, the materials eventually flow within a finite time and cannot behave as elastomers; in other words, they are merely supramolecular polymers that have only transient cross-links or bonds. Therefore, the key to preparing higher-performance supramolecular elastomers is their molecular design. Here, we firstly review the fundamental design of supramolecular polymers to make the differences between supramolecular polymers and supramolecular elastomers clear. Second, we discuss the simultaneous incorporation of (semi)permanent cross-links and supramolecular cross-links into polymeric materials to prepare supramolecular elastomers. Finally we summarized their properties and potential applications.

DOI： 10.1016/j.polymer.2017.03.010

Block copolymer-based supramolecular elastomers

Noro A., Kajita T., Matsushita Y.

International Polymer Science and Technology 44 巻 ( 9 ) 頁： 1 - 6 2017年9月

Enthalpy-Driven Swelling of Photonic Block Polymer Films 査読有り

Noro, A; Tomita, Y; Matsushita, Y; Thomas, EL

MACROMOLECULES 49 巻 ( 23 ) 頁： 8971 - 8979 2016年12月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Macromolecules

Nonvolatile, soft photonic films that reflect UV/vis light were prepared by enthalpy-driven swelling of lamellar-forming polystyrene-b-poly(2-vinylpyridine) (PS-P2VP) block copolymer thin films with a neat protic solvent. These films are very sensitive to further swelling with the addition of a small amount of acid. Transmission electron microscopy and ultrasmall-angle X-ray scattering of the films before and after the addition of the neat protic solvent revealed selective swelling of the P2VP phase while maintaining the lamellar morphology due to the presence of the layered glassy PS domains. P2VP is swollen due to the hydrogen bonding between a hydroxy group of a protic solvent and the pyridyl group of P2VP. The interdomain distance of the neat PS-P2VP film as measured by U-SAXS increased by about 200% and the films acted as a 1D photonic crystal reflecting UV light. Moreover, by exposing the neat PS-P2VP films to a mixture of a protic solvent and a small amount of sulfonic acid that can protonate the pyridyl groups of the P2VP block, the degree of swelling, therefore the interdomain distance and the wavelength of the reflection light, became significantly larger, resulting in color variations across the visible spectrum and suggesting that such a nonvolatile material system can be a sensor of the acid concentration in the millimolar regime for anhydrous solutions.

DOI： 10.1021/acs.macromol.6b01867

Highly Extensible Supramolecular Elastomers with Large Stress Generation Capability Originating from Multiple Hydrogen Bonds on the Long Soft Network Strands 査読有り

Hayashi, M; Noro, A; Matsushita, Y

MACROMOLECULAR RAPID COMMUNICATIONS 37 巻 ( 8 ) 頁： 678 - 684 2016年4月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Macromolecular Rapid Communications

Highly extensible supramolecular elastomers are prepared from ABA triblock-type copolymers bearing glassy end blocks and a long soft middle block with multiple hydrogen bonds. The copolymer used is polystyrene-b-[poly(butyl acrylate)-co-polyacrylamide]-b-polystyrene (S-Ba-S), which is synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Tensile tests reveal that the breaking elongation (ϵb) increases with an increase in the middle block molecular weight (Mmiddle). Especially, the largest S-Ba-S with Mmiddle of 3140k, which is synthesized via high-pressure RAFT polymerization, achieves ϵb of over 2000% with a maximum tensile stress of 3.6 MPa, while the control sample without any middle block hydrogen bonds, polystyrene-b-poly(butyl acrylate)-b-polystyrene with Mmiddle of 2780k, is merely a viscous material due to the large volume fraction of soft block. Thus, incorporation of hydrogen bonds into the large molecular weight soft middle block is found to be beneficial to prepare supramolecular elastomers attaining high extensibility and sufficiently large stress generation ability simultaneously. This outcome is probably due to concerted combination of entropic changes and internal potential energy changes originating from the dissociation of multiple hydrogen bonds by elongation.

DOI： 10.1002/marc.201500663

ブロック共重合体超分子エラストマー招待有り査読有り

野呂篤史，梶田貴都，松下裕秀

日本ゴム協会誌 90 巻 ( 1 ) 頁： 9-13 2015年12月

高分子自己組織化と分子間相互作用制御を基盤とした高性能ソフト材料の創製招待有り

野呂篤史

東海化学工業会報 287 巻頁： 5-8 2015年7月

Mechanical Property Enhancement of ABA Block Copolymer-Based Elastomers by Incorporating Transient Cross-Links into Soft Middle Block 査読有り

Hayashi, M; Matsushima, S; Noro, A; Matsushita, Y

MACROMOLECULES 48 巻 ( 2 ) 頁： 421 - 431 2015年1月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Macromolecules

We propose a new strategy to enhance mechanical properties of ABA triblock copolymer-based elastomers by incorporating transient cross-links into the soft middle block. An ABA triblock-type copolymer, poly(4-vinylpyridine)-b-[(poly(butyl acrylate)-co-polyacrylamide]-b-poly(4-vinylpyridine) (P-Ba-P), was synthesized via RAFT polymerization. In the molecular design, the poly(4-vinylpyridine) (P) end blocks with a high Tg formed pseudo-crosslink domains due to segregation against the soft Ba middle block, while acrylamide units on the middle block formed self-complementary hydrogen bonding, serving as transient crosslinks. According to tensile tests, the Young's modulus, elongation at break, maximum stress, and material toughness were 1.9 MPa, 200%, 2.6 MPa, and 2.8 MJ/m3, respectively. Comparison between mechanical properties of P-Ba-P and those of another triblock copolymer, poly(4-vinylpyridine)-b-poly(butyl acrylate)-b-poly(4-vinylpyridine) (P-B-P), revealed that P-Ba-P showed larger Young's modulus, longer elongation at break, and larger maximum tensile stress than P-B-P. Particularly, the material toughness of P-Ba-P (2.8 MJ/m3) was more than 100 times larger than that of P-B-P (0.02 MJ/m3). Rheological analysis on the basis of sticky Rouse relaxation of Ba middle block of P-Ba-P suggested that the hydrogen bonds on the middle block serve as dynamic stickers in elastic strands of elastomers under stress. Such dynamic behavior of the hydrogen bonds could prevent local concentration of applied stress for activating break/failure of the materials during elongation, leading to mechanical property enhancement of the materials. In addition, zinc chloride was blended with P-Ba-P to form metal-ligand coordination in the P end block domains, which also affected the mechanical properties of the elastomers. (Chemical Equation Presented).

DOI： 10.1021/ma502239w

Design and viscoelasticity control of supramolecular soft materials bearing noncovalent cross-links 招待有り査読有り

Noro A.

Nihon Reoroji Gakkaishi 43 巻 ( 5 ) 頁： 125 - 133 2015年

担当区分：筆頭著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Nihon Reoroji Gakkaishi

Well-controlled molecular design of supramolecular polymer gels, which can be prepared by incorporating noncovalent cross-links strategically, was proposed. In fact, supramolecular polymer gels were prepared by blending poly(2-vinylpyridine)-b-poly(ethyl acrylate)-b-poly(2-vinylpyridine) triblock copolymer (V-EA-V), poly(4-hydroxystyrene) homopolymer (H), and a nonvolatile ionic liquid (IL), where the two polymers were synthesized via reversible addition fragmentation chain transfer polymerization. The supramolecular polymer gels contained an IL as a solvent; therefore, they were called supramolecular supramacromolecular ion gels. The supramolecular ion gels represented gel-like behavior at lower temperatures whereas they flowed within a normal timescale (several seconds) at higher temperatures. Such behavior was found to be thermoreversible. Master curves prepared from frequency-dependent viscoelastic spectra on the basis of time-temperature superposition principle exhibit the plateau modulus with approximately 10 orders of magnitude in reduced frequency. It was also revealed from temperature dependency of shift factors that the longest relaxation time at a low temperature such as 50 °C was as long as 109 s. Decrement of shift factors at lower temperatures was smaller than that of shift factors at higher temperatures. This is because the origin of relaxation is formation 7 dissociation of hydrogen bonds. When the concentration of H in solution blends was varied and that of V-EA-V was kept almost the same, the temperature at G' G" (TG'=G") increased with an increase in H concentration. The sharpness of the change in G' against the temperature near TG'=G" depends on the phenol pyridine stoichiometric ratio and the number of branches of V end blocks from one H polymer. Furthermore, it was also revealed from small angle X-ray scattering measurements that supramolecular gelationlsupramolecular cross-linking was associated with formation of nanophase-separated structure. Knowledge acquired here is useful for development of novel functional soft materials and analysis interpretation of viscoelastic behavior of such materials.

DOI： 10.1678/rheology.43.125

Design and Viscoelasticity Control of Supramolecular Soft Materials Bearing Noncovalent Cross-Links

Noro, A

NIHON REOROJI GAKKAISHI 43 巻 ( 5 ) 頁： 125 - 133 2015年

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