Synthesis of polymerizable anionic surfactants and their emulsion copolymerization with styrene

Abstract

Two polymerizable ionic surfactants sodium 4-(ω-acryloyloxyalkyl)oxy benzene sulfonate (SABS-n, n = 8 or 10) have been synthesized and polymerized. Their critical micelle concentrations (CMC) were determined to be 9.40 × 10-3 M and 2.02 × 10-3 M at 25 °C for SABS-8 and SABS-10, respectively. The rate of micellar polymerization of SABS-8 or SABS-10 was found to be proportional to half an order of the concentration of ammonium persulfate (APS) and first order of the surfactant concentration. Their activation energies of micellar polymerization were relatively low, that is, 58.2 kJ mol-1 for SABS-8 and 45.4 kJ mol-1 for SABS-10. The monomer reactivity ratios for emulsion copolymerization of SABS-8 (M1) and styrene (M2) were determined to be r1 = 0.47 and r2 = 3.91. These emulsion copolymerizations produced small latex particles ranging from 16 to 30 nm in diameter. XPS analysis shows that SABS-8 was significantly enriched on the surface of latex particles, for example, 63.4% surface coverage on latex particles by 16 wt % SABS-8 in the feed composition. The surface coverage of about 20% polymerized surfactant on the surface of latex particles was found to be sufficient to stabilize latexes under heating at 70 °C for at least one month.