Synthesis and Characterization of a Novel Addition-Fragmentation Reactive Surfactant (TRANSURF) for Use in Free-Radical Emulsion Polymerizations

摘要

The synthesis and characterization of a new type of chain- transfer-active surfactant (i.e., TRANSURF) is reported. The com- pound 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 influ- ence of surfactant migration during film fonnation. Surfactants of this type, containing two hydrophilic head groups, can have a marked influence on the polymer and latex properties (e.g., molec- ular 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 "bolafonn" (a, w) (Zana, R., in "Structure-Perfonnance Relationships in Surfactants" (K. Esumi and M. Ueno, Eds.), Surfactant Science Series 70, Dekker, New York, 1997) structure the micelle fonnation 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 molecularconfonnation was evident at 1 x 10-3 moldm-3 (131 A2 surface area), which we assumed to correspond to the low aggrega- tion 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.