Cationic Thermoresponsive Poly(N-vinylcaprolactam) Microgels Synthesized by Emulsion Polymerization Using a Reactive Cationic Macro-RAFT Agent

Abstract

A series of reactive poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) (P(AETAC)) cationic polymers with varying degrees of polymerization were synthesized by RAFT/MADIX polymerization and investigated as stabilizers for the emulsion polymerization of N-vinylcaprolactam (PVCL) in the presence of a cross-linker. It was demonstrated that the xanthate chain end of the cationic P(AETAC-X) polymers played a crucial role to produce stable cationic PVCL-based microgels at higher initial solids content (5–10 wt %) than usually reported for the synthesis of PVCL microgels. The thermoresponsive PVCL microgels with cationic shell undergo a reversible volume shrinkage upon heating in the absence of any hysteresis in accordance with the narrow particle size distribution. The values of the volume phase transition temperature ranged between 28 and 30 °C for the microgels synthesized using 4 and 8 wt % of P(AETAC-X) based on VCL. The presence of a cationic outer shell onto the microgels was evidenced by the positive...