Reactive surfactants in heterophase polymerisation - XXIII. Synthesis and characterisation of novel dialkyl maleate cationic surfmers

A series of alkyl pyridinium bromide maleate diester surfmers were synthesised together with their saturated non-polymerisable succinate analogues. Each series consisted of four surfactants with the maleate or succinate function at different positions on the alkyl chain with the integrated length of the alkyl chain being more or less constant. The surface activity was evaluated and the critical micelle concentration (cmc) was found to be dramatically affected by the position of the maleate or succinate group. For the cases in which the pyridinium ring was close to the carboxylate group of the maleate or succinate, all the experimental observations could be explained if there was an interaction between the cationic N centre and the ester(s) reducing the charge density of the headgroup and, for example, allowing a closer packing of the molecules at the air-water interface. Overall, however, these species behaved similarly to conventional surfactants such as cetylpyridinium bromide. Those species in which the maleate or succinate,group was placed in the terminal position of the hydrophobic tail showed abnormally high (similar to X 10) critical micelle concentrations suggesting that the polar group in this position reduced considerably the overall hydrophobic nature of the surfactant tail. These molecules also appear to adopt a looped conformation at the air-water interface. (C) 1998 Elsevier Science Ltd. All rights reserved.