How to toughen polymer gels with entropy-mediated reversible crosslinking*

Materials composed of polymers that are permanently crosslinked into a network, such as gels and rubbers, eventually break if strained enough. This is because the network irreversibly ruptures once the local forces acting on the polymers and crosslinks become too large for the bonds to withstand. Recent experiments have revealed that adding *reversible* crosslinks to a gel allows it to be strained to a much larger extent, yet without altering its small-strain elasticity [1]. We are using theory, molecular simulation, and polymer self-consistent field theory for networks, to explore reversible crosslinking as a design paradigm for creating polymer materials that are tough but elastic [2]. Emphasis will be placed on how entropy itself drives reversible crosslinks to toughen the material, while preserving its intrinsic elasticity. Practical guidelines will be outlined to optimise this design in experiment, along with a discussion of key kinetic and timescale considerations.

[1] Kean, Z. S.; et al. Adv. Mat. 2014, 26, 6013. Mayumi, K.; et al. Extreme Mech. Lett. 2016, 6, 52.
[2] Tito, N. B.; Creton, C.; Storm, C; Ellenbroek, W. G. arXiv preprint (https://arxiv.org/abs/1810.10079).