Title: Exploring the interplay between electrostatics and hydrophobicity on dense suspensions of thermo-responsive microgels

Authors: Sayantan Chanda 1, Chandeshwar Misra 1 and Ranjini Bandyopadhyay 1

1Rheology and Dynamic light scattering lab, Soft condensed matter department, Raman Research Institute, Bengaluru, India - 560080.

PNIPAMs are well known microgel particles which undergo a reversible volume phase transition from being hydrophilic to hydrophobic with increase in temperature above a critical value known as LCST [1]. We use rheology to study the modification in their inter-particle interaction by systematically adding various dissociative and non-dissociative additives into the suspension. In linear viscoelastic regime, elasticity of the suspensions goes down with increase in additive concentration below LCST. Above LCST though, there is an additive induced crossover from viscoelastic solid to viscoelastic liquid. Under high applied shear (non- linear regime) the suspensions show single step yielding below LCST and two-step yielding above LCST [2]. The values of yield strains both below and above LCST is governed by both the nature and quantity of additive used.

References:

1. Heskins et. al, 1968 J. Macromol Sci. 2 1441.

2. Zhou et.al, Langmuir, 2014, 30, 5739−5746.