Nonionic cleavable ortho ester surfactants

A new class of cleavable surfactants based on the ortho ester link is described. Ortho ester surfactants were synthesized from a short‐chain ortho ester, a fatty alcohol, and a poly(ethylene glycol) monomethyl ether. The triple functionality of the ortho ester link results in a mixture of surface‐active and nonsurface‐active species. Structures were confirmed by 1H and 13C nuclear magnetic resonance. Hydrolysis characteristics at pH values ranging from 2 to 8 were determined. It was shown that, after a steep rise, hydrolysis curves flattened out before complete hydrolysis was reached. Ortho ester surfactants hydrolyze more rapidly than corresponding acetal surfactants. Hydrolysis rates are higher for purified samples and at higher temeprature, while plateau levels are higher for the purified surfactant mixtures and at lower pH. The origin of these results is discussed. Data also indicate that the hydrolysis mechanism changes with pH. A test of the loss of emulsification capacity for an ortho ester surfactant with time at pH values from 2 to 11.5 and at 22 or 50°C was carried out, showing rapid breaking of the emulsion at mild acid conditions and a requirement of pH≥10 for long‐term stability. Surface tension and critical micelle concentration were determined for some of the surfactant mixtures. It was demonstrated that ortho ester surfactants possess excellent biodegradation properties. The new surfactants are promising candidates for use in industrial processes where temporary surfactant action is required.