Synthesis and characterization of a novel addition-fragmentation reactive surfactant (TRANSURF) for use in free-radical emulsion polymerizations

The synthesis and characterization of a new type of chain-transfer-active surfactant (i.e., TRANSURF) is reported. The compound was designed on the basis of the chemistry of macromers, which undergo free-radical chain-transfer addition–fragmentation reactions. In effect this allows incorporation of the surfactant molecule into the polymer backbone, and thus reduces the influence of surfactant migration during film formation. Surfactants of this type, containing two hydrophilic head groups, can have a marked influence on the polymer and latex properties (e.g., molecular weight distributions and particle size). Characterization of the physical properties of this surfactant was therefore carried out using surface tension, conductivity, and fluorescence techniques. Because of the surfactant's unusual "bolaform" (a, ¿) (Zana, R., in "Structure–Performance Relationships in Surfactants" (K. Esumi and M. Ueno, Eds.), Surfactant Science Series 70, Dekker, New York, 1997) structure the micelle formation process has been found to be quite different from that of the conventional surfactant, sodium dodecyl sulfate (SDS). From the surface tension data a flat molecular conformation was evident at 1×10-3 mol dm-3 (131 Å2 surface area), which we assumed to correspond to the low aggregation number of premicellar aggregates. There is evidence to suggest formation of a larger volume of the microdomains in these micelles compared to that in SDS. At higher TRANSURF concentrations, however, we find no clear indication of a switch to a "wicket"-type conformation, although such conformational changes cannot be ruled out.