PHASE-BEHAVIOR OF TELECHELIC POLYISOBUTYLENE (PIB) IN SUBCRITICAL ANDSUPERCRITICAL FLUIDS .2. PIB SIZE, SOLVENT POLARITY, AND INTER-ASSOCIATION AND INTRA-ASSOCIATION EFFECTS FOR BLANK, MONOHYDROXY, AND DIHYDROXY PIB(11K) IN ETHANE, PROPANE, CARBON-DIOXIDE, AND DIMETHYL ETHER

Cloudpoints for monohydroxy, dihydroxy, and nonfunctional (referred tb as blank) telechelic polyisobutylene df molecular weight 11000 g/mol (PIB(11K)) were measured up to 200 degrees C and 2000 bar in ethane, p ropane, and dimethyl ether and compared to those for polyisobutylene o f molecular weight 200 g/mol (PIB(200)) and 1000 g/mol (PIB(1K)). The PIB size, solvent polarity,and,hydroxy group density were found to inf luence the balance of self-association, cross-association, or intra-as sociation. Each of these types of association uniquely shifts the clou d-point curves relative to the nonassociating system. The statistical associating fluid theory (SAFT) rigorously accounts for these shifts i f they are due to intermolecular association. If these shifts are due to intramolecular association as found in polar solutions, effective S AFT sites and parameters have to be used to fit the experimental data.