Influence of particle size on the thermoresponsive and rheological properties of aqueous poly(N-isopropylacrylamide) colloidal suspensions

TL;DR

This study investigates how particle size, controlled by SDS concentration, affects the thermoresponsive swelling and rheological behavior of PNIPAM colloidal suspensions, revealing size-dependent properties.

Contribution

It introduces a one-pot synthesis method to produce PNIPAM particles of varying sizes and analyzes their thermoresponsive and rheological properties in detail.

Findings

Smaller particles have higher swelling ratios.

Particle size decreases with increased SDS concentration.

Rheological behavior varies with particle size.

Abstract

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) particles of different sizes are synthesized by varying the concentration of sodium dodecyl sulphate (SDS) in a one-pot method. The sizes, size polydispersities and the thermoresponsivity of the PNIPAM particles are characterized by using dynamic light scattering and scanning electron microscopy. It is observed that the sizes of these particles decrease with increase in SDS concentration. Swelling ratios of PNIPAM particles measured from the thermoresponsive curves are observed to increase with decrease in particle size. This observation is understood by minimizing the Helmholtz free energy of the system with respect to the swelling ratio of the particles. Finally, the dynamics of these particles in jammed aqueous suspensions are investigated by performing rheological measurements.