Polymerizable nonionic microemulsions: Phase behavior of H2O-n-alkyl methacrylate-n-alkyl poly(ethylene glycol) ether (CiEj)

The phase behavior of ternary water-alkyl methacrylate-alkyl polyglycol eth er (CiEj) systems has been examined. Specifically, using seven different al kyl methacrylates ranging from methyl to hexadecyl methacrylate and C10E6 a s surfactant, vertical sections through the phase prism were determined, fr om which the phase inversion temperature, the upper and lower critical temp erature of the three-phase body, and the efficiency of the surfactant and i ts monomeric solubility in the oil were obtained. Keeping hexyl methacrylat e as oil-fixed, 18 different surfactants were applied including short- and long-chain surfactants such as C4E3 and C14E8 The microemulsion systems exa mined here show the same general patterns as the well-known nonionic microe mulsions with alkanes as oil. Notably, the phase inversion temperature is h ighly dependent on the alkyl chain length of the oil, a fact that is often left out of consideration when choosing a surfactant in emulsion polymeriza tion. For a given oil the phase inversion temperature can be adjusted by ap propriate choice of the number of ethylene glycol units of the surfactant. The efficiency of the surfactant systematically depends on the alkyl chain length of both the surfactant and the oil. Interestingly, there is a striki ng parallel between efficiency of a surfactant and its monomeric solubility in the oil. Finally, in preparation for applying these systems to the synt hesis of nanoscaled latexes in microemulsion polymerization the water-rich part of the phase prism was examined. Both the expected shape of the emulsi fication failure phase boundary and the near-critical phase boundary with i ts nonmonotonic decay characteristic of branched network structures are del ineated. The results of some preliminary polymerizations are briefly discus sed.