Encapsulated Clay Particles in Polystyrene by RAFT Mediated Miniemulsion Polymerization

RAFT grafted montmorillonite (MMT) clays [i.e., NN-dimethyl-N-(4(((phenylcarbonothioyl)thio)methyl)benzyl)ethanammonium-MMT (PCDBAB-MMT) and N-(4-((((dodecylthio)carbonothioyl)thio)methyl)benzyl)-N,N-dimethylethanammonium-MMT (DCTBAB-MMT)] of various loadings were dispersed in styrene (S) monomer and the resultant mixtures emulsified and sonicated in the presence of a hydrophobe (hexadecane) into miniemulsions. The stable miniemulsions thus obtained were polymerized to yield encapsulated polystyrene-clay nanocomposites (PS-CNs). The molar mass and polydispersity index (PDI) of the PS-CNs depended on the amount of RAFT agent in the system, in accordance with the features of the RAFT process. The morphology of the PS-CNs ranged from partially exfoliated to an intercalated morphology, depending on the percentage clay loading. The thermomechanical properties of the PS-CNs were better than those of the neat PS polymer, and were dependent on the molar mass, PS-CN morphology and clay loading. The similarities and differences of the PS-CNs prepared here by miniemulsion polymerization were compared to those prepared using the same RAFT agents and polymer system by bulk polymerization (as reported by us in a previous article). (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7114-7126, 2008