Microemulsion polymerization of styrene stabilized by sodium dodecyl sulfate and diethylene glycol monoalkyl ether

The effects of the cosurfactants diethylene glycol monoalkyl ether [CiH2i (+) O-1(CH2CH2O)(j)OH (CiEj; i = 4, 6 and j = 1, 2)] on the formation of an oil-in-water styrene (ST) microemulsion and the subsequent free radical polymerization were studied. For comparison, the data for the CiH2i + iOH (CiOH; i = 4, 6) systems obtained from the literature were also included in this work. Sodium dodecyl sulfate was used as the surfactant. The pseudo three-component phase diagram (macroemulsion, microemulsion and lamellar gel phases) was constructed for each cosurfactant. The primary parameters selected for the polymerization study are the concentrations of cosurfactant and styrene. The number of latex particles nucleated is much smaller than that of the microemulsion droplets initially present in the reaction system. Limited flocculation of the latex particles occurs to some extent during polymerization. Among the cosurfactants investigated, the C4OH-containing polymerization system is the least stable. By contrast, the diethylene glycol monoalkyl ether group of CiEj tends to enhance the latex stability. CiEj is more effective in stabilizing the ST microemulsion and the subsequent polymerization in comparison with the CiOH counterpart.