SELF-ASSEMBLY OF Y(OXYBUTYLENE)-POLY(OXYETHYLENE)-POLY(OXYBUTYLENE) (B6E46B6) TRIBLOCK COPOLYMER IN AQUEOUS-SOLUTION

Laser light scattering and small-angle neutron scattering were used to study y(oxybutylene)-poly(oxyethylene)-poly(oxybutylene) triblock cop olymers (B6E46B6) in aqueous solution from low to high concentrations and over a range of temperatures from 5 to 35 degrees C. B6E46B6 molec ules exist as unimers at low concentrations and low temperatures. At h igher concentrations and at low temperature (less than or equal to 15 degrees C), they associate in small numbers and scattering evidence sh ows that molecular associates with open structures might form. At high er temperatures, typical flowerlike micelles form. The critical micell e concentration decreases with increasing temperature while the associ ation number increases. At high polymer concentrations (e.g., at 35% i n mass), further entanglements form among the micelles, yielding anoth er slow mode in dynamic light scattering, which can be attributed to t he bridging of two hydrophobic end blacks located iu two different hyd rophobic clusters by the hydrophilic middle block. However, these cros s-linkings were quite weak and free micelles were still the majority i n solution. When the temperature is lowered, a very slow process of mi crophase separation occurs. The self-assembly behavior of B6E46B6 is c ompared with that of other BEB type triblock copolymers.