Radical generation process studies of the cationic surfactants in ultrasonically irradiated emulsion polymerization

Without any chemical initiators added, ultrasonically irradiated emulsion copolymerization of styrene and a cationic polymerizable surfactant (methacryloxyethyl dodecydimethyl ammonium bromide, C12N+) was successfully employed to prepare copolymer nanolatexes. Compared with the conventional ionic surfactants, C12N+ has much higher initiation efficiency and C12N+ system exhibits shorter induction period, much higher styrene conversions and polymerization rate Rp in short reaction time. A radical trapping experiment and gas chromatograph–mass spectrograph analysis proved that under ultrasonic irradiation, C12N+ undergoes bond scission between the two alkyl and ionic group, where both C–N bonds are weak along the chain, thereby producing much more original radicals to initiate the emulsion polymerization.