Mechanism of emulsion polymerization of styrene using a reactive surfactant

The emulsion polymerization of styrene using the reactive surfactant sodium dodecyl allyl sulfosuceinate (TREM LF-40) was studied. The polymerization kinetics were found to be unusual in that RP was not directly proportional to NP (RP, N-p(0.67)). Several reasons are stated to explain the unusual ki netics, including chain transfer to TREM LF-40, copolymerization of styrene with TREM LF-40, and the influence of the homopolymer of TREM LF-40 [poly( TREM)] and/or the copolymer [poly(TREM-co-styrene)] on the entry and exit r ates of free radicals. The possibility of both chain transfer and copolymer ization exists primarily at the oil/water interface, whereas both can also occur in the aqueous and monomer phases. Bulk polymerizations of styrene in the presence of TREM LF-40 and poly(TREM) were conducted, and the results show that the reaction rate decreased for the styrene/TREM LF-40 system. La tex characterization by serum replacement and titration measurements provid ed evidence for the chemical bonding of TREM LF-40 to the polymer particles . The fraction of chemically bound reactive surfactant decreased with incre asing surfactant concentration and increased with increasing initiator conc entration. Relatively high contact angles of water on films cast from the l atexes showed that TREM LF-40 did not migrate significantly to the surface of the film, which was consistent with the latex-surface characterization r esults. (C) 2001 John Wiley & Sons, Inc.