Dynamical signatures of the vulcanization transition

TL;DR

This paper models the dynamical behavior of vulcanized polymer networks, revealing critical slowing down at the vulcanization transition and distinct relaxation features in sol and gel phases.

Contribution

It introduces a Rouse-type model incorporating permanent random crosslinks to analyze dynamical signatures of the vulcanization transition.

Findings

Kohlrausch relaxation in the sol phase at any nonzero crosslink density

Divergence of the longest relaxation time at the critical point

Algebraic decay of scattering function at the transition, persistent gel fraction in the gel phase

Abstract

Dynamical properties of vulcanized polymer networks are addressed via a Rouse-type model that incorporates the effect of permanent random crosslinks. The incoherent intermediate scattering function is computed in the sol and gel phases, and at the vulcanization transition between them. At any nonzero crosslink density within the sol phase Kohlrausch relaxation is found. The critical point is signalled by divergence of the longest time-scale, and at this point the scattering function decays algebraically, whereas within the gel phase it acquires a time-persistent part identified with the gel fraction.