The University of Tokyo · 재료과학
카즈아키 카토 교수의 연구실은 주로 고분자 상전이와 유변학적 거동을 다루는 고도로 설계된 슬라이드링 고분자 시스템, 특히 폴리로타제인 젤의 동적 거동과 고무성질 간의 상관관계를 중심으로 연구를 전개하고 있습니다. 특히, 고리형 고분자(예: 시클로덱스트린)가 선형 고분자에 스며들어 상호 작용하는 '인터록킹 구조'를 통해 고체의 거칠기와 유동성의 균형을 제어하는 신개념 젤 및 고무 재료의 설계 원리를 규명하고 있습니다. 이들의 연구는 고분자 설계의 새로운 패러다임을 제시하며, 생체재료, 유연 전자소자, 스마트 염료 등 응용 분야로의 확장이 기대됩니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
A systematic study of the viscoelastic relaxation of slide-ring gels revealed the dynamics of chains sliding through the cross-links, based on a precise assignment of the plateau moduli and on detailed consideration of the correlation between relaxation times and the molecular weights between cross-links. The slide-ring gels exhibit finite equilibrium moduli that are much smaller than those of the rubbery plateau, indicating a significant contribution of the ring components’ entropy to the elast
Modification of the guest polymer ends efficiently and substantially decreases the density of the threaded rings. The minimized ring density drastically facilitates chain sliding through the cross-links in polyrotaxane gels. This molecular design is like regulating the "pressure" of the rings confined in the interlocked architecture, which counteracts the sliding.
The universal relationship between the elastic modulus and the cross-link density of a conventional rubber/gel has been demonstrated experimentally to be inapplicable to gels with slidable cross-links. Herein, we describe the synthesis of slide-ring (SR) gel networks devoid of intramolecular cross-links by the cross-coupling of two differently functionalized polyrotaxanes. The cross-link density was determined from the characteristic UV absorption attributed to the asymmetric cross-linked moiety
Double-digit relaxation of the elastic modulus and a previously unknown plateau are observed in a new class of slide-ring gels. Detailed consideration of the assignment of the two observed plateaus and the relaxation dynamics reveals that the relaxation is attributable to the sliding dynamics of partial chains through cross-links. This suggests a transition between one state where the cross-links behave as fixed ones and another where they slide freely.
A novel polyrotaxane consisting of poly(dimethylsiloxane) (PDMS) and γ-cyclodextrin (γ-CD) is synthesized, and the threaded γ-CDs of polyrotaxane are intermolecularly cross-linked in solution to yield a new class of slide-ring gel. Synthesis of the polyrotaxane is achieved by an end-capping reaction of pseudo-polyrotaxane whose both ends are preliminarily activated as p-nitrophenyl ester with p-methoxytritylamine derivatives. The obtained polyrotaxane is soluble in N,N-dimethylformamide (DMF) an
We report herein a versatile synthesis of cyclodextrin-based polyrotaxanes (CD-PRs). Three different CD-PRs were synthesized from different linear polymers and different CDs with relatively good yields by a novel single method. This method requires no additional capping reagents, because CDs play a dual role as both the cyclic components and the end-capping groups. The end-capping is achieved by transesterification with excess CDs at both ends of pseudopolyrotaxanes activated with p-nitrophenyl
A new class of ductile glasses is created from a thermoplastic polyrotaxane. The hard glass, which has a Young's modulus of 1 GPa, shows crazing, necking, and strain hardening with a total elongation of 330%. Stress concentration is prevented through a unique stretch-induced intramolecular phase separation of the cyclic components and the exposed backbone. In situ synchrotron X-ray scattering studies indicate that the backbone polymer chains slip through the cyclic components in the regions wher
The molecular dynamics of condensed polymers are directly linked to practically important mechanical properties, such as glass transition behavior and impact strength. We present a unique viscoelastic glass-forming polyrotaxane that is comprised of a main chain polymer and threaded cyclodextrins. The abnormally broad glass transition phase is attributed to the segment motion, which is unprecedentedly insusceptible to cooperative motion with neighboring chains until vitrification is completed. Ev
Topological constraints in polyrotaxanes significantly affected their glass transition dynamics. The effects of the constraints were systematically studied using a series of different coverage glass-forming polyrotaxanes consisting of a common polymer and threaded ring molecule of varying ratios. Although their ratios were similar and hence exhibited similar <i>T</i><sub>g</sub> values by differential thermal analysis, mechanical relaxation was considerably prolonged with increasing coverage. Th
A simple molecular design based on the size of the cyclic components of polyrotaxanes achieved a significant variation of mechanical relaxation dynamics of polyrotaxane gels.
A series of polyrotaxane glasses composed of poly(ethylene glycol) backbones and threaded α-cyclodextrins (α-CDs) with different substituents were found to exhibit unique viscoelasticities attributed to their interlocked structures, beyond a mere miscible blend of the different components. Differences in the interactions between CDs, which occupied 80 wt % or more of the materials, brought about wide variations in the glass transition temperature and also influenced the cooperativity of segmenta
Pure (2R,3S)-3-methyl-2-pentanol is resolved from the racemates by a steroidal host; the interpretation of the recognition mechanism based on the crystal structure reveals that CH/O interaction between the host and guest plays a decisive role in enantio-selective enclathration of the small aliphatic secondary alcohol.
