Influence of Molecular Architecture on the Viscoelastic Properties of Polymers with Phase-Separated Dynamic Bonds

Abstract

Polymers with dynamic bonds attract significant attention due to their many unique properties, such as self-healing and recycling. However, understanding microscopic mechanisms controlling their dynamics and viscoelastic properties, especially in the case of phase-separated dynamic bonds, remains rather limited. We present analysis of model polymer systems with phase-separating dynamic bonds (stickers) placed along the chain (pendant stickers) or at the end of the chain (telechelic systems). We demonstrate that the bond rearrangement process in these systems is controlled by the pullout of a sticker from a cluster, with the characteristic time defined by structural relaxation in clusters and miscibility of stickers in the polymer matrix. This enables decoupling of terminal relaxation from segmental dynamics of the polymer. The analysis revealed the critical role of the total concentration of stickers that controls dynamics of the polymer in the broad time range from segmental relaxation up to the time of sticker pullout from a cluster, regardless of the sticker placement on the chain and the length of the chain. Only at longer time scales, the molecular length and sticker placement influence viscoelastic properties. Based on these results, we suggest a general scenario for mechanisms controlling the dynamics and viscoelasticity of polymers with phase-separated dynamic bonds. This scenario can be helpful in guiding the design of dynamic polymers with desired viscoelastic properties.