Volume phase transitions of poly(N-isopropylacrylamide) latex particles in mixed water-N,N-dimethylformamide solutions

Volume phase transitions of poly(N-isopropylacrylamide) (PNIPAM) latex particles in mixed water-N,N-dimethylformamide (DMF) solutions were studied at different temperatures and crosslink densities using dynamic light scattering. A collapse-swelling behaviour was observed on the addition of N,N-dimethylformamide to an aqueous dispersion medium. The degree of swelling was found to be dependent on the temperature and crosslink density. The transition between the collapsed state and the swollen state was continuous. The cononsolvency of water and DMF for PNIPAM latex particles has been interpreted in terms of the changes in the interactions between their components.