Mesophase behavior of aqueous micellar solutions of triblock copolymers of ethylene oxide and 1,2-butylene oxide (type EmBnEm)

Solutions of copolymers E21B10E21 and E35B10E35 were studied by rheometry, polarized light microscopy, small-angle X-ray scattering, and small-angle neutron scattering. With increase in concentration, both copolymers first form a body-centered cubic hard gel. Comparison is made with published results (Langmuir 1998, 14, 5782) for the related copolymer E16B10E16, which first forms a hexagonal hard gel. Published values of the association numbers of the micelles were used to characterize the stretching of the B blocks in the micelle cores, hence the tendency to form cylindrical micelles and so hexagonal hard gels. Soft gels were detected at concentrations below and at temperatures below and above the boundaries for hard gel formation.