SYNTHESIS AND EVALUATION OF A SURFACE-ACTIVE PHOTOINITIATOR FOR MICROEMULSION POLYMERIZATION

The first water-soluble perester that can serve as a surface-active ph otoinitiator for polymerization has been synthesized. This photoinitia tor showed a good solubility in water and a sufficient molar absorptiv ity in the WA region. While heat-activated decomposition of this perox ide in an aqueous solution leads mainly to heterolytic cleavage of the dioxy bond, its photochemical decomposition gives predominately homol ytic cleavage. When the perester was used as an initiator in microemul sion polymerization of styrene, stable and relative monodispersed poly styrene latices were Obtained. The produced polystyrene has a high mol ecular weight in the range of 10(4)-10(6) and a narrow molecular weigh t distribution (MWD = M-W/M-n similar to 2.5). The initiator is locate d at the interface, and the polymerization may be initiated with the s eparation of two radicals which are generated at the interface. The la tex characteristics such as particle size, polydispersity, molecular w eight, and molecular weight distribution depend on the nature of the s urfactant and the way by which the radicals are generated.