Glass and Jamming Rheology in Soft Particles Made of PNIPAM and Polyacrylic Acid
Silvia Franco, Elena Buratti, Valentina Nigro, Emanuela Zaccarelli, Barbara Ruzicka, Roberta Angelini
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(N-isopropylacrylamide) (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.