A SAXS study of the structure of gels formed by mixtures of polyoxyalkylene triblock copolymers

Abstract

Small-angle X-ray scattering was used to characterise aqueous micellar gels of triblock copolymers E137S18E137, E82S9E82, E76S5E76, E62P39E62, and of two mixtures: E137S18E137 and E62P39E62 (Mix 1) and E82S9E82 and E62P39E62 (Mix 2), each 50/50 wt%. E = oxyethylene, CH2CH2O; S = oxyphenylethylene, OCH2CH(C6H5); and P = oxypropylene, OCH2CH(CH3). Within the concentration and temperature ranges investigated (30-40 wt% copolymer, 20-80 °C), spherical micelles of copolymers E137S18E137, E82S9E82 and E62P39E62 packed into body-centred cubic (BCC) structures. Gels of E76S5E76 were stable only at high concentrations and low temperatures, and a 70 wt% copolymer solution at T = 30°C formed a hexagonal gel consistent with cylindrical micelles. It is likely that the mixed copolymers would form two distributions of micelles, and more complex structures were expected. However, gels of Mix 2 had well-ordered BCC structures, while the less ordered gels of Mix 1 were also best characterised as BCC. © 2006 Society of Chemical Industry.