EFFECT OF CYCLIZATION ON THE ASSOCIATION BEHAVIOR OF BLOCK-COPOLYMERSIN AQUEOUS-SOLUTION - COMPARISON OF OXYETHYLENE OXYPROPYLENE BLOCK-COPOLYMERS CYCLO-P34E104 AND E52P34E52/

Triblock copolymer E52P34E52 was prepared by sequential anionic polyme rization of propylene oxide followed by ethylene oxide. Some of this c opolymer was cyclized via acetal closure to yield a cyclic diblock cop olymer, cyclo-P34E104, which was characterized by gel permeation chrom atography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. Lig ht scattering methods were used to study the micellization and micella r properties of the two copolymers: dynamic light scattering for hydro dynamic properties of the micelles, static light scattering for micell ar molar mass and critical micellization conditions. The gelation of c oncentrated solutions was also studied. The critical micelle concentra tions (cmc) of the two copolymers were similar for solutions at 40-50 degrees C, but the temperature dependence of the cmc was smaller for t he linear copolymer. The cyclic copolymer in solution at 50-55 degrees C formed micelles with larger association numbers and hard-sphere vol umes than its linear triblock counterpart.