Dynamics of Associative Polymers with High Density of Reversible Bonds

TL;DR

This study explores how high densities of reversible hydrogen bonds in associative polymers influence their dynamics, revealing a universal exponential increase in relaxation time and challenging classic models.

Contribution

It introduces a new renormalized Rouse model to explain the dynamics of high-sticker-density associative polymers, surpassing traditional sticky-Rouse model limitations.

Findings

Reversible bonds slow down polymer dynamics significantly.

Structural relaxation time increases exponentially with sticker fraction.

Viscoelastic spectra shape remains largely unchanged.

Abstract

We design and synthesize unentangled associative polymers carrying unprecedented high fractions of stickers, up to eight per Kuhn segment, that can form strong pairwise hydrogen bonding of $\sim20k_BT$ without microphase separation. The reversible bonds significantly slow down the polymer dynamics but nearly do not change the shape of linear viscoelastic spectra. Moreover, the structural relaxation time of associative polymers increases exponentially with the fraction of stickers and exhibits a universal yet non-Arrhenius dependence on the distance from polymer glass transition temperature. These results cannot be understood within the framework of the classic sticky-Rouse model but are rationalized by a renormalized Rouse model, which highlights an unexpected influence of reversible bonds on the structural relaxation rather than the shape of viscoelastic spectra for associative polymers with high concentrations of stickers.