Percolation in a Model Transient Network: Rheology and Dynamic Light Scattering

TL;DR

This study investigates the viscoelastic behavior and dynamic structure of a percolating droplet microemulsion with telechelic polymers, revealing relaxation dynamics and critical behavior near the percolation threshold.

Contribution

It provides new insights into the relaxation dynamics and critical exponents of transient networks formed in microemulsions with telechelic polymers, challenging mean field models.

Findings

Both stress relaxation time and dynamic structure factor slow time vanish at the percolation threshold.

Relaxation times follow power-law behavior with different exponents.

The system exhibits two-step relaxation dynamics in the structure factor.

Abstract

Step strain experiments and dynamic light scattering measurements are perfomed to characterize the dynamic behavior of an o/w droplet microemulsion into which is incorporated a telechelic polymer. At sufficient droplet and polymer concentrations, above the percolation threshold, the system is viscoelastic and its dynamic structure factor shows up two steps for the relaxation of concentration fluctuations: the fast one is dominated by the diffusion but the slower one is almost independent of the wave vector. The terminal time of the stress relaxation tR and the slow time of the dynamic structure factor tS are both presumably controlled by the residence time of a sticker in a droplet: consistently, tR and tS are of the same order, they both vanishes at the percolation threshold according to power laws but with different exponents. We discuss these features in terms of deviations at the transition, from the usual mean field description of the dynamics of transient networks.