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arXiv · 1601.07706

Glass-like dynamics of the strain-induced coil/helix transition on a permanent polymer network

O. Ronsin·C. Caroli·T Baumberger
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Abstract

We study the stress response to a step strain of covalently bonded gelatin gels in the temperature range where triple helix reversible crosslink formation is prohibited. We observe slow stress relaxation towards a $T$-dependent finite asymptotic level. We show that this is assignable to the strain-induced coil $\rightarrow$ helix transition, previously evidenced by S. Courty, J.L. Gornall and E.M. Terentjev (PNAS, {\bf 102}, 13453 (2005)), of a fraction of the polymer strands. Relaxation proceeds, in a first stage, according to a stretched exponential dynamics, then crosses over to a terminal simple exponential decay. The respective characteristic times $τ_{K}$ and $τ_{f}$ exhibit an Arrhenius-like $T$-dependence with an associated energy $\cal E$ incompatibly larger than the activation barrier height for the isomerisation process which sets the clock for an elementary coil $\to$ helix transformation event. We tentatively assign this glass-like slowing down of the dynamics to the long-range couplings due to the mechanical noise generated by the local elementary events in this random elastic medium.

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O. Ronsin, C. Caroli, T Baumberger. 2016-01-28. Glass-like dynamics of the strain-induced coil/helix transition on a permanent polymer network. https://doi.org/10.1063/1.4941456

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