By cross-linking multiple pairs of cyclodextrin (CD) molecules on polyethylene glycol (PEG) based polyrotaxane (PR) chains, and letting solvent intrude into the obtained PR network, slide-ring (SR) gels are prepared. The sliding movement of figure-of-eight cross-links within SR gels reduces stress concentration in deformed polymer network. Therefore, compared with fixed cross-link (FC) gels cross-linked by covalent bonds, improved fracture toughness has recently been reported for SR gels. In this work, we try to reveal the influence of CD coverage on the fracture toughness of SR gels and thus the influence on the sliding movement of figure-of-eight cross-links. With the amount of CDs on one PR chain decreases from 100 to around 10, the fracture energy increases from 4 J/m2 to 50 J/m2. During the fracture process, the stress-strain distribution at the crack-tip of SR gels is for the first time directly observed via polarized light high-speed camera. Reduced stress concentration and around 10 times enlargement of fracture zone suggest wider slidable range of cross-links as the CD coverage decreases. The positive effort of unique molecular behavior leads one toward new strategies of enhancing fracture toughness of polymer networks.

Large deformation and fracture behavior of slide-ring gels with different cyclodextrin coverages

256th National Meeting (2018)

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