Simple synthesis of a library of zwitterionic surfactants via Michael-type addition of methacrylate and alkane thiol compounds.

A library of zwitterionic phosphorylcholine surfactants with various alkyl chain lengths and compositions was readily prepared from a combination of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and various alkanethiol compounds via Michael-type addition. The critical micelle concentration (CMC) was evaluated by surface tensiometry. At the CMC, the surface tension of these aqueous solutions decreased significantly to below 40 mN/m. For the zwitterionic surfactants composed of MPC, and fluoroalkane and alkanedithiol, the surface tension was approximately 24, and 50 mN/m, respectively. From the equation log (CMC) = A - Bn, where n is the number of carbon atoms in the alkyl chain, A and B were calculated as 1.09 and 0.44, respectively. The value of the slope B was between that of ionic (B = 0.30) and nonionic surfactants (B = 0.50). Despite the ionic nature of the surfactants, their behavior was closer to that of nonionic surfactants.