PHASE-BEHAVIOR OF INVERSE MICROEMULSIONS FOR THE POLYMERIZATION OF ACRYLAMIDE IN NEAR-CRITICAL AND SUPERCRITICAL CONTINUOUS PHASES

The inverse microemulsion polymerization of water-soluble acrylamide monomers within near-critical and supercritical alkane continuous phases provides a potential route for production of polymers with novel physical properties and at high reaction rates. In order to define conditions for a model polymerization process, the phase behavior of a nonionic surfactant/acrylamide/water system in near-critical and supercritical mixtures of ethane and propane was examined. Acrylamide was found to act as a cosurfactant due to its short chain length and hydrophilic character and thus is probably coordinated about the surfactant's ethylene oxide units at the interface, rather than residing in the micelle core. The effects of temperature and composition on the phase behavior can be qualitatively explained from results on CiEj/water/alkane systems at atmospheric pressure by using either generalized ternary liquid-phase diagrams or a model that considers micelle-micelle and micelle-fluid interactions.