Thermoresponsive redispersible polystyrene latexes

Redispersible polystyrene (PS) latexes with particle sizes in the range of 250 nm were prepared using low-molecular-weight amphiphilic thermoresponsive polymeric surfactants. A series of linear polymers with cetyl/stearyl as hydrophobic part and poly(2-methyloxazoline)/poly(2- ethyloxazoline) with about ten repeat units were synthesized through cationic ring opening polymerization (CROP) and were used as nonionic surfactants (NIS) in the preparation of poly(styrene) latexes by batch emulsion polymerization. Latexes prepared with surfactant containing thermoresponsive segments upon being heated yielded a white coagulant above its LCST temperature at 85 oC and redispersed upon cooling with minimal stirring. The particle sizes measured at 25 oC confirmed that the pristine and redispersed latex had almost similar size, whereas at 85 oC an abrupt change in the particle sizes were observed. This promising result shows the excellent use of thermoresponsive surfactant for the preparation of readily redispersible polystyrene latexes.