Behavior of thermo- and pH-responsive copolymer of N-isopropylacrylamide and maleic acid in aqueous solutions

ABSTRACT

A thermo- and pH-responsive copolymer of N-isopropylacrylamide with maleic acid was studied using light scattering and turbidimetry methods. Aqueous solutions with pH values from 1.8 to 10.9 and in the concentration range from 0.001 to 0.015 g/cm³ were investigated. At all pH values and concentrations, phase separation was observed at temperatures T > 33°C. The temperatures of the start and the width of the phase separation interval increased with decrease of copolymer concentration and increase in pH. The redistribution of scattering entities, namely, macromolecular unimers, micelle-like structures, and loose aggregates, and growth of aggregate hydrodynamic radius took place during heating.

KEYWORDS:

• Aggregation
• copolymer of N-isopropylacrylamide and maleic acid
• light scattering and turbidimetry
• phase separation
• thermo- and pH-responsive polymers