PHASE-BEHAVIOR OF TELECHELIC POLYISOBUTYLENE (PIB) IN SUBCRITICAL ANDSUPERCRITICAL 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), mo nohydroxy, and dihydroxy telechelic polyisobutylene were measured in e thane, propane, chlorodifluoromethane, dimethyl ether, and carbon diox ide up to 200 degrees C and 2000 bar. These amorphous polyisobutylene samples of molecular weight around 1000 are nearly monodisperse and ha ve zero, one, or two terminal hydroxy groups. In nonpolar solvents, th e 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 stati stical associating fluid theory (SAFT).