Since chemical single network gel is a basic unit in the soft matter field, its mechanical performance plays decisive role on the property of various gel composite. Traditional chemical gels are generally brittle owing to the inhomogeneous structure. Tough gels reported thus far usually contain sacrificial species to dissipate energy, and thus compromising the fatigue resistance. This work attempts to explore and achieve the mechanical performance limit of a polymer network, by taking full advantage of the slide-ring effect. In this study, cyclodextrin (CD, the host)-based polyrotaxanes (PRs) with the same axis (polyethylene glycol (PEG)) but different host coverages are synthesized, and used to prepare the slide-ring gels. With the decreasing of the host coverage from 25% to 2%, the slide range of the CD cross-links is increased from 18% to 65% axis length in corresponding gels. The low coverage allows the crosslinks to freely slip along the chain in wide interval, and thus the polymer strands can be fully utilized to avoid the failure of the network under large deformation (Fig.1 (a)). The hydrogels based on 2% covered PR can withstand ~1MPa stress and more than 1200% strain, which is the best mechanical properties for all reported chemical single-network hydrogel and even comparable to some energy-dissipating gels, but still instantly recoverable (Fig.1 (b)). As the PEG axis in the low covered PR is almost exposed without the shelter of CDs, the DMSO gels based on 2% covered PR exhibits a reversible shape memory behavior due to the synergy of the slide-ring effect and orientation-induced PEG crystallization. It is noted that the slide-ring effect can be introduce into various structural materials by using polyrotaxane as crosslinker, and thus this work not only pushes the performance envelope of soft matters, but also provides a novel insight to design tough materials.

Slipping in wide interval: Polyrotaxane with low host coverage and its tough slide-ring gels

256th National Meeting (2018)

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