Relationship between the network dynamics, supramolecular relaxation time and healing kinetics of cobalt poly(butyl acrylate) ionomers

The aim of this work is to contribute to the understanding of the relationship between the timescales of molecular processes in ionomers and that of macroscale autonomous healing. For this purpose, poly(butyl acrylate-co-acrylic acid) model ionomers with varying fractions of cobalt counter ions were used. Three temperature dependent timescales were quantified and linked: (i) the terminal relaxation time (t(d)) as determined by creep relaxation experiments; (ii) the supramolecular relaxation timescale (tau) as determined by frequency sweeps in oscillatory shear rheology; and (iii) the macroscopic healing timescale (t(heal)) as obtained by quantifying the time for full interfacial strength recovery for two ionomer surfaces brought in contact. Using the temperature dependent values of t(d), tau, and t(heal), the activation energies of the ionic cluster formation, the flow of the polymer backbone, and the interfacial recovery respectively, were calculated. It was found that the kinetics of healing closely follows the timescales of network and cluster formation. (C) 2015 Elsevier Ltd. All rights reserved.