Cationic Polymerizations in Supercritical Carbon Dioxide

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Carbocationic polymerizations are used extensively in large volume industrial processes (for example, butyl rubbers and isobutylene-based industries). These polymerizations are commonly carried out in toxic chlorinated hydrocarbon solvents, many thousands of pounds of which end up yearly in the atmosphere. This project is an investigation into the possibility of replacing these polluting solvents with the environmentally neutral, inexpensive carbon dioxide as the all-purpose solvents for Friedel-Crafts acids mediated polymerizations, and beyond these, to Friedel-Crafts acid catalyzed reactions in general. The first specific thrust will be the demonstration that the toxic solvents can be replaced with supercritical carbon dioxide in carbocationic polymerizations and copolymerizations, and to elucidate the scope and fundamentals of these processes. This will be followed by explorations into Friedel-Crafts acid catalyzed reactions, such as alkylation, sulfonation, acetylation, etc. The effects of pressure, temperature, and reagent concentrations in supercritical carbon dioxide will be explored. The initial phase of the polymerization studies will concern common monomers (isobutylene, styrene and its derivatives, and conjugated dienes such as isoprene), coinitiators, and small amounts of additives (cosolvents, proton traps, electron donors, and salts).