Synthesis, characterization, and temperature-dependent colloidal stability of poly(N-isopropylacrylamide)-grafted polystyrene/poly(styrene-co-4-vinylbenzyl N, N-diethyldithiocarbamate) hairy particles

Abstract

Poly(N-isopropylacrylamide)-grafted polystyrene/ poly(styrene-co-4-vinylbenzyl N, N-diethyldithiocarbamate) (PNIPAM-grafted PS/P(St-co-VBDC)) hairy particles were synthesized by photo-polymerizing N-isopropylacrylamide monomer in the presence of PS/P(St-co-VBDC) core par- ticles. Here, the VBDC unit, which was incorporated into the surface of core particles by seeded soap-free emulsion copolymerization, acted as a photo-iniferter. By varying the polymerization conditions, a series of hairy particles having different grafting heights and grafting densities was success- fullyobtained.Thehairyparticlesexhibitedwell-definedcore/ shell morphology. PS/P(St-co-VBDC) formed the core which was surrounded by PNIPAM shell. The determination of critical coagulation concentration (CCC) indicated that the hairy particles were stabilized via both electrostatic and steric mechanisms (i.e., electrosteric mechanism) at a temperature lower than LCST of PNIPAM. However, these particles gave muchlowerCCCs whenheatedtothe temperature higherthan LCST, exhibiting temperature-dependent colloidal stability.