PHASE-BEHAVIOR OF TELECHELIC POLYISOBUTYLENE (PIB) IN SUBCRITICAL AND SUPERCRITICAL FLUIDS .1. INTER-ASSOCIATION AND INTRA-ASSOCIATION EFFECTS FOR BLANK, MONOHYDROXY, AND DIHYDROXY PIB(1K) IN ETHANE, PROPANE, DIMETHYL ETHER, CARBON-DIOXIDE, AND CHLORODIFLUOROMETHANE

The cloud-point pressures for nonfunctional (referred to as blank), monohydroxy, and dihydroxy telechelic polyisobutylene were measured in ethane, propane, chlorodifluoromethane, dimethyl ether, and carbon dioxide up to 200 degrees C and 2000 bar. These amorphous polyisobutylene samples of molecular weight around 1000 are nearly monodisperse and have zero, one, or two terminal hydroxy groups. In nonpolar solvents, the hydroxy groups increase the cloud-point pressures. In polar solvents, however, one group increases but two groups decrease the cloud-point pleasures. These shifts in pressures are interpreted on the basis of intermolecular and intramolecular association estimated from the statistical associating fluid theory (SAFT).