Thermoplastic elastomers are typically block- or brush-copolymers that microphase separate into ‘hard’ glassy or crystalline domains embedded in a ‘soft’ rubbery matrix. However, it is difficult to introduce a large energy dissipation capacity, self-recovering and adhesive property due to a lack of mobility of polymer chains. We reasoned that if hard domains that do not have any covalent connectivity with soft segments using a polyrotaxane structure were introduced, we might be able to obtain a high stretchability as well as a self-recovering and adhesive property. Recently we synthesized a novel polyrotaxane made of 2-(trimethylsilyloxy)propyl a-cyclodextrins and poly(ethylene glycol) (TMSP-PR). TMSP-PR showed a large tan d value (&gt;0.5) and no distinguished relaxation over a wide range of frequencies (0.001 – 100 Hz). In order to investigate a self-recovering property of TMSP-PR, repeated cyclic stress–strain tests were conducted. TMSP-PR showed pronounced hysteresis with a maximum applied strain of 80%, which indicates energy dissipation. However, when the same film was allowed to rest for one hour, and stretched again, it showed self-recovery—that is, a very similar behavior to that of the original stress–strain ones (Figure). This material also showed adhesive property. In order to investigate self-assembled structure imparting the mechanical properties mentioned above, the size and regularity of the domains made of a-cyclodextrins were investigated using wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) under deformation of the sample and after the deformation. It was found that the SAXS profiles went back to the original SAXS profile after one hour of elongation, which indicates that the dynamic self-assembly of the a-cyclodextrins is contributing to the unique mechanical property of TMSP-PR.

Highly stretchable self-recovering and adhesive polyrotaxane thermoplastic elastomer

256th National Meeting (2018)

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