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

Polymers with dynamic bonds attractsignificant attention due totheir many unique properties, such as self-healing and recycling.However, understanding microscopic mechanisms controlling their dynamicsand viscoelastic properties, especially in the case of phase-separateddynamic bonds, remains rather limited. We present analysis of modelpolymer systems with phase-separating dynamic bonds (stickers) placedalong the chain (pendant stickers) or at the end of the chain (telechelicsystems). We demonstrate that the bond rearrangement process in thesesystems is controlled by the pullout of a sticker from a cluster,with the characteristic time defined by structural relaxation in clustersand miscibility of stickers in the polymer matrix. This enables decouplingof terminal relaxation from segmental dynamics of the polymer. Theanalysis revealed the critical role of the total concentration ofstickers that controls dynamics of the polymer in the broad time rangefrom segmental relaxation up to the time of sticker pullout from acluster, regardless of the sticker placement on the chain and thelength of the chain. Only at longer time scales, the molecular lengthand sticker placement influence viscoelastic properties. Based onthese results, we suggest a general scenario for mechanisms controllingthe dynamics and viscoelasticity of polymers with phase-separateddynamic bonds. This scenario can be helpful in guiding the designof dynamic polymers with desired viscoelastic properties.