We demonstrate that block copolymers of the poly(ethylenepropylene)-co-poly(ethylene oxide) (PEP−PEO) type dramatically enhance the solubilization capacity of medium-chain surfactants in microemulsions, for example, in the ternary system water−n-decane−C10E4. The effect exhibits itself in an enormous increase of the swelling of the middle phase with an associated increase in the structural length scale of the microemulsion, while at the same time the (already ultralow) interfacial tension between water- and oil-rich phases decreases even further. Typically, the surfactant mass fraction γ0 = 0.13 sufficient to form the balanced one-phase microemulsion in the ternary system can be replaced by γ = 0.035 of surfactant plus polymer. If δ is the polymer mass fraction in the surfactant/polymer mixture, the overall mass fraction of polymer in the microemulsion amounts only to γδ = 0.004. Accordingly, in this example the polymer is f B = 24 times more efficient than the surfactant, where we define an efficiency boost factor by f B = (γ0 − γ(1 − δ))/γδ. The magnitude of the effect depends to some extent on the overall molar mass of the polymer but rather weakly on the relative size of the hydrophilic and hydrophobic blocks. Interestingly, the lamellar phase, which usually develops as surfactants become more efficient, is suppressed.

The phase behavior of ternary water−alkyl methacrylate−alkyl polyglycol ether (C i E j ) systems has been examined. Specifically, using seven different alkyl methacrylates ranging from methyl to hexadecyl methacrylate and C10E6 as surfactant, vertical sections through the phase prism were determined, from which the phase inversion temperature, the upper and lower critical temperature of the three-phase body, and the efficiency of the surfactant and its monomeric solubility in the oil were obtained. Keeping hexyl methacrylate as oil-fixed, 18 different surfactants were applied including short- and long-chain surfactants such as C4E3 and C14E8. The microemulsion systems examined here show the same general patterns as the well-known nonionic microemulsions with alkanes as oil. Notably, the phase inversion temperature is highly dependent on the alkyl chain length of the oil, a fact that is often left out of consideration when choosing a surfactant in emulsion polymerization. For a given oil the phase inversion temperature can be adjusted by appropriate 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 striking parallel between efficiency of a surfactant and its monomeric solubility in the oil. Finally, in preparation for applying these systems to the synthesis of nanoscaled latexes in microemulsion polymerization the water-rich part of the phase prism was examined. Both the expected shape of the emulsification failure phase boundary and the near-critical phase boundary with its nonmonotonic decay characteristic of branched network structures are delineated. The results of some preliminary polymerizations are briefly discussed.