Robust Phase Behavior of Model Transient networks

TL;DR

This study investigates the phase behavior of model transient networks formed by microemulsion droplets linked with telechelic polymers, revealing a large monophasic region with distinct fluid and gel phases, and a two-phase region at low volume fractions.

Contribution

It presents a detailed experimental analysis of four different microemulsion-polymer systems, highlighting their phase behavior and the influence of molecular variations on network dynamics.

Findings

Identification of a large monophasic region with fluid and gel sub-phases

Observation of a two-phase region at low volume fractions

Correlation between molecular structure and phase behavior

Abstract

In order to study the viscoelastic properties of certain complex fluids which are described in terms of a multiconnected transient network we have developed a convenient model system composed of microemulsion droplets linked by telechelic polymers. The phase behavior of such systems has two characteristic features: a large monophasic region which consists of two sub-regions (a fluid sol phase and a viscoelastic gel phase) separated by a percolation line and a two phase region at low volume fraction with separation into a dilute sol phase and a concentrated gel phase. From the plausible origin of these features we expect them to be very similar in different systems. We describe here the phase behavior of four different systems we prepared in order to vary the time scale of the dynamical response of the transient network; they consist of the combination of two oil(decane) in water microemulsions differing by the stabilizing surfactant monolayer (Cetyl pyridinium chloride/octanol or TX100/TX35) and of two telechelic polymers which are end-grafted poly (ethylene oxide) chains, differing by the end-grafted hydrophobic aliphatic chains (C12H25 or C18H37).