The role of cationic monomers in emulsion polymerization

[2-(methacryloyloxy)ethyl] trimethylammonium chloride (MATMAC), and vinylbenzyl trimethyl ammonium chloride (VBTMAC) were chosen to be used as ionic comonomers in the emulsion polymerization of styrene. The cationic nature of the two comonomers is the same (quaternary ammonium salts), however the styrene derivate (VBTMAC) is more hydrophobic than the methacrylic one (MATMAC). With the more hydrophobic cationic comonomer (VBTMAC) higher conversions were obtained due to the in situ creation of an amphiphilic copolymer with styrene and faster rates of polymerization were observed by increasing the cationic comonomer concentration. The same behavior was observed with the more hydrophilic cationic comonomer (MATMAC) at concentrations up to 0.012 M. At higher concentrations the ionic strength controls the colloidal stability of the system and coagulation occurs.