title: Glass-like dynamics of the strain-induced coil/helix transition on a permanent polymer network.
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 → helix transition, previously evidenced by Courty et al. [Proc. Natl. Acad. Sci. U. S. A. 102, 13457 (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 τK and τf exhibit an Arrhenius-like T-dependence with an associated energy E incompatibly larger than the activation barrier height for the isomerisation process which sets the clock for an elementary coil → 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.
authors.affiliation: Institut des NanoSciences de Paris, CNRS, Sorbonne Université-Pierre et Marie Curie, UMR 7588, 4 Place Jussieu, 75005 Paris, France.
authors.forename: O
authors.initials: O
authors.lastname: Ronsin
authors.affiliation: Institut des NanoSciences de Paris, CNRS, Sorbonne Université-Pierre et Marie Curie, UMR 7588, 4 Place Jussieu, 75005 Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Caroli
authors.affiliation: Institut des NanoSciences de Paris, CNRS, Sorbonne Université-Pierre et Marie Curie, UMR 7588, 4 Place Jussieu, 75005 Paris, France.
authors.forename: T
authors.initials: T
authors.lastname: Baumberger
mesh_terms: D004548:Elasticity; D005780:Gelatin / Q000737:chemistry*; D005898:Glass / Q000737:chemistry*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*
chemical_list: D011108:Polymers; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D005780:Gelatin