Impact of Fluorination and Side-Chain Length on Poly(methylpropenoxyalkylsiloxane) and Poly(alkyl methacrylate) Solubility in Supercritical Carbon Dioxide

A great deal of interest has been generated within the past few decades on supercritical fluid technology applied to polymerization processes, polymer purification and fractionation processes, and solution coatings and powder formation processes. A critical issue for each of these potential applications is the determination of polymer solubility in supercritical carbon dioxide, a highly preferred processing solvent. There exists a fair amount of experimental data on solubility of polymers and copolymers in CO₂ from which it is possible to obtain insight into the properties of the polymer that control solubility. It is now well-known that fluorinating a polymer enhances its solubility in supercritical CO₂; however, it is also accepted that polymer polarity and backbone flexibility also have a strong influence on the temperatures and pressures needed to dissolve a polymer in supercritical CO. In addition, it has been shown that fluorinating an alkyl side chain improves polymer solubility, and likewise, it has been shown that polymer solubility decreases significantly as the length of a nonfluorinated alkyl side chain is increased.