Selective Sorption and Desorption of Organic Solvent for δ-Syndiotactic Polystyrene

The desorption and sorption kinetics of organic solvents in the cavity of δ- and empty δ-forms of syndiotactic polystyrene (sPS) were investigated as a function of molar volume and shape of the solvent molecules. The desorption process was performed for films cast from chloroform, benzene, chlorobenzene, toluene, and p-xylene in supercritical CO2 at 40 °C and 10 MPa. The nanoporous structure of δ-sPS after extraction of solvent molecules was dependent on the solvent used. Large size solvent molecules were slowly excluded from δ-sPS. The relation between the cavity volume of δ-sPS and the dimensions of the solvent molecule suggests that desorption is slow for solvent molecules that are tightly packed in the cavities. The sorption kinetics of alcohols was investigated as a function of chain length using the nanoporous structure of empty δ-sPS. When empty δ-sPS was soaked in a linear alcohols with carbon numbers from 1 to 10, the alcohols with carbon number less than 6 could be incorporated in the cavity of empty δ-sPS. The diffusion coefficient of alcohols into the cavity was estimated using the Fickian equation. The diffusion became slower for longer chain length alcohols. In order to compare the sorption of different molecular shaped alcohols, structural isomers of 4 and 5 carbon number alcohols were investigated. These isomers were classified into two categories; alcohols with hydroxyl side groups and those with methyl side groups. Alcohols with hydroxyl side groups could be incorporated into empty δ-sPS; however, the methyl side group prevented the insertion of alcohol molecules into the cavity of empty δ-sPS.