For the development of pH-sensitive surfactants to be used in water-in-oil fermentation, the free-radical terpolymerization of methacrylic acid (MAA), methoxy poly(ethylene glycol) methacrylate (MPEGMA), and lauryl methacrylate (LMA), at a molar ratio of 1.0:0.04:0.76, was studied with two initiators, azobisisobutyronitrile (AIBN) and hydrogen peroxide, at different concentrations. The polymer synthesized with 0.45% AIBN as the initiator was the most promising, giving similar conversions of all three monomers throughout the 10-h polymerization. The subsequent study on AIBN-initiated systems indicated that MPEGMA caused an increase-then-decrease profile of the MAA conversion with a plateau around an ethylene glycol/MAA ratio of 1-2. This observation was fairly consistent with the well-known type II template polymerization of poly(ethylene glycol) (PEG)-MAA systems. The reactivity ratios obtained in this study suggested that the polymer synthesized with AIBN as the initiator had a structure of alternating blocks of AMA and LMA, with isolated PEG grafts. (C) 2004 Wiley Periodicals, Inc.