ASSOCIATION BEHAVIOR OF A TRIBLOCK COPOLYMER OF OXYETHYLENE (E) AND OXYBUTYLENE (B) - A STUDY OF B(5)E(91)B(5) IN AQUEOUS-SOLUTION

Static and dynamic light-scattering experiments were performed to stud y the association behavior of a BEB-type (B and E represent poly(oxybu tylene) and poly(oxyethylene), respectively) triblock copolymer, B(5)E (91)B(5), in aqueous solution from dilute to concentrated solution reg ions over a range of temperature (15.5-45.0 degrees C). B(5)E(91)B(5) is soluble in water at low temperatures. At 15.5 degrees C and concent rations below 3% (w/v), only unimers are present. At higher temperatur es and in the dilute solution region, the degree of association and th e aggregation number increase, while the critical micelle concentratio n decreases with increasing temperature. The existence of branched ass ociated structures is suggested in the concentrated solution region, w here interconnected micelles are in coexistence with small molecular a ssociates (or premicelles) and the average size of these interconnecte d micelles appears to increase with increasing concentration.