Glass and Jamming Rheology in Soft Particles Made of PNIPAM and Polyacrylic Acid

TL;DR

This study investigates the complex flow behaviors of soft colloids made from PNIPAM and PAAc microgels, revealing transitions from fluid to glassy and jammed states as concentration increases.

Contribution

It provides new rheological data on interpenetrated polymer network microgels and identifies three distinct states with potential molecular mechanisms.

Findings

Identified Newtonian shear-thinning fluid behavior.

Detected attractive glass with yield stress.

Observed jamming transition at high concentrations.

Abstract

The phase behaviour of soft colloids has attracted great attention due to the large variety of new phenomenologies emerging from their ability to pack at very high volume fractions. Here we report rheological measurements on interpenetrated polymer network microgels composed of poly(Nisopropylacrylamide) (PNIPAM) and polyacrylic acid (PAAc) at fixed PAAc content as a function of weight concentration. We found three different rheological regimes characteristic of three different states: a Newtonian shear-thinning fluid, an attractive glass characterized by a yield stress, and a jamming state. We discuss the possible molecular mechanisms driving the formation of these states.