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 pol ymerization were studied. For comparison, the data for the CiH2i + iOH (CiO H; i = 4, 6) systems obtained from the literature were also included in thi s work. Sodium dodecyl sulfate was used as the surfactant. The pseudo three -component phase diagram (macroemulsion, microemulsion and lamellar gel pha ses) was constructed for each cosurfactant. The primary parameters selected for the polymerization study are the concentrations of cosurfactant and st yrene. The number of latex particles nucleated is much smaller than that of the microemulsion droplets initially present in the reaction system. Limit ed flocculation of the latex particles occurs to some extent during polymer ization. Among the cosurfactants investigated, the C4OH-containing polymeri zation system is the least stable. By contrast, the diethylene glycol monoa lkyl ether group of CiEj tends to enhance the latex stability. CiEj is more effective in stabilizing the ST microemulsion and the subsequent polymeriz ation in comparison with the CiOH counterpart.