Dynamic Light Scattering Study of Temperature and pH Sensitive Colloidal Microgels

TL;DR

This study uses dynamic light scattering to analyze how temperature, pH, and concentration affect the swelling behavior of IPN microgels made of PNIPAM and PAAc, revealing reversible volume phase transitions and pH-dependent differences.

Contribution

It provides new insights into the combined temperature and pH sensitivity of IPN microgels and their transition behavior under different conditions.

Findings

Identification of thermoreversible swelling-shrinking transition.

pH influences the transition process due to PAAc presence.

Distinct behaviors observed at acidic and neutral pH.

Abstract

Microgel particles composed of Interpenetrated Polymer Networks (IPN) of poly(N-isopropylacrylamide) (PNIPAM) and poly(acrylic acid) (PAAc) dispersed in water have been investigated through dynamic light scattering. The study of the temperature, concentration and pH dependence of the relaxation time has highlighted the existence of a thermoreversible transition corresponding to the swollen-shrunken volume phase transition. The presence of PAAc introduces an additional pH-sensitivity with respect to the temperature-sensitivity due to PNIPAM and leads to interesting differences in the transition process at acid and neutral pH.