Journal of Polymer Science Part A: Polymer Chemistry, Vol.39, No.18, 3093-3105, 2001
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 kinetics, 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 rates of free radicals. The possibility of both chain transfer and copolymerization 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. Latex characterization by serum replacement and titration measurements provided evidence for the chemical bonding of TREM LF-40 to the polymer particles. The fraction of chemically bound reactive surfactant decreased with increasing surfactant concentration and increased with increasing initiator concentration. Relatively high contact angles of water on films cast from the latexes showed that TREM LF-40 did not migrate significantly to the surface of the film, which was consistent with the latex-surface characterization results.