Three oxyethylene/oxybutylene triblock copolymers of similar E-block length but different B-block lengths (B4E40B4, B5E39B5, and B7E40B7) were prepared by sequential anionic polymerization and characterized by gel permeation chromatography and NMR spectroscopy. Their association in aqueous solution was investigated by static and dynamic light scattering, and evidence was found for small molecular associates, micelles, and micelle clusters (bridged micelles). Values of the critical micelle concentrations and micellar association numbers were determined and compared with those for related diblock (EmBn) and triblock (EmBnEm) copolymers.

The association properties of block copolymers of ethylene oxide (E) and 1,2-butylene oxide (B) manufactured by The Dow Chemical Company were studied by static and dynamic light scattering. The critical micelle concentrations and micelle association numbers so obtained were combined with literature values for related copolymers in order to discuss the effect of block architecture on the association properties of linear diblock and triblock copolymers. The measurements significantly increase the available data for E m B n E m triblock copolymers and provide new insight into effects caused by E-block distributions originating from the different rates of reaction of ethylene oxide with primary and secondary oxyanions during copolymerization.

A series of diblock copolymers E,oBn, with n in the range 3 to 16, was prepared by sequential anionic polymerization, and the association behavior of the copolymers in aqueous solution was investigated, as was the gelation of their concentrated micellar solutions. At temperatures in the range 30-50 'C, a minimum B-block length of four to five units was required for micellization. Gelation of micellar solutions of the copolymers was observed for copolymers with B-block lengths of six to seven units or more. The relationships between (i) standard Gibbs energy of micellization and molecular characteristics and (ii) critical gelation concentration and micellar characteristics were explored.

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Gels of a poly(oxyethylene)−poly(oxybutylene) diblock copolymer in aqueous solution forming a bcc phase have been examined using small-angle X-ray scattering (SAXS) with simultaneous rheology. Application of large amplitude oscillatory shear is observed to induce macroscopic alignment of twinned bcc crystals. Alignment at relatively low frequency leads to a structure in which {200} planes are oriented normal to the shear direction. At high frequency, large amplitude shearing leads to a transition to flow with the [111] plane parallel to the shear direction. Flow occurs in the {110} and {211} planes which intersect along the same [111] direction, leading to a high-symmetry SAXS pattern with numerous sharp reflections. These results highlight the similarity between the defect mechanics of cubic phases in block copolymer gels and those in metals.