BEHAVIOR OF AQUEOUS-SOLUTIONS OF POLY(ETHYLENE OXIDE-B-PROPYLENE OXIDE) COPOLYMERS CONTAINING A HYDROTROPIC AGENT

The effect of the hydrotropic agent, sodium p -toluenesulfonate (NaPTS ), was evaluated on the micelle formation process and on phase behavio r of aqueous solutions containing poly(ethylene oxide-b-propylene oxid e) (PEO-PPO) copolymers. We have studied monofunctional diblock copoly mers coupled with hydrocarbons groups (R-PEO-PPO-OH and R-PPO-PEO-OH, where R length is linear C-4 and C12-14) The critical micelle concentr ation (CMC) and critical micelle temperature (CMT) values of the aqueo us copolymers solutions were obtained from both surface tension versus concentration plots and the dye solubilization method. The influence of the hydrocarbons groups length and PPO segment position in the stru cture of the copolymers were also analyzed. The same measures were obt ained for the aqueous solutions of hydrotropic agent which, in turn, a lso presented molecular aggregation. The presence of the hydrotropic a gent in the aqueous copolymers solutions altered the surface tension o f these solutions and the occupied molecular area per copolymer molecu le at air-water interface and CMC and CMT values of the copolymers. On the other hand, the aggregation points and the surface tension of the NaPTS solutions were dependent on the copolymer structure and composi tion. (C) 1998 John Wiley & Sons, Inc.