PHASE-BEHAVIOR OF AQUEOUS SYSTEMS CONTAINING BLOCK-COPOLYMERS OF POLY(ETHYLENE OXIDE) AND POLY(PROPYLENE OXIDE)

Phase behavior of aqueous systems containing block, copolymers of poly (ethylene oxide (PEG) and poly(propylene oxide) (PPO) was evaluated by building up temperature-concentration phase diagrams. We have studied bifunctional triblock copolymers (HO-PEO-PPO-PEO-OH) and monofunction al diblock copolymers (R-PEO-PPO-OH and R-PPO-PEO-OH, where R length i s linear C-4 and C12-14) The cloud points of the polymer solutions dep ended on EO/PO ratio, polarity, R length and position of the hydrophil ic and hydrophobic segments along the molecule. Such factors influence on the solutions behavior was also analyzed in terms of critical mice lle concentration (CMC), which was obtained from surface tension vs. c oncentration plots. Salts (NaCl and KCl) added into the polymer soluti ons change the solvent polarity decreasing the cloud points. On the ot her hand, the cloud points of the polymer solutions increased as a hyd rotrope (sodium p-toluenesulfonate) was added. (C) 1997 John Wiley & S ons, Inc.