Simultaneous rheology and small-angle scattering experiments on block copolymer gels and melts in cubic phases

A new instrument for simultaneous small-angle X-ray scattering and rheology experiments on soft solids is described. This device is based on a commercial rheometer with a shear sandwich geometry in which the sample is subjected to a planar oscillatory deformation. This instrument has been used for time-resolved small-angle X-ray scattering/rheology experiments at the Synchrotron Radiation Source, Daresbury Laboratory, England. The focus has been in particular on the effect of large-amplitude shearing on the orientation of cubic phases in gels of block copolymers formed in concentrated solutions, and on the bicontinuous cubic phase of a block copolymer melt. Representative results are presented for face-centred cubic (f.c.c.) and body centred cubic (b.c.c.) phases in gels of poly(oxyethylene)-poly(oxybutylene) diblock copolymers, and for the bicontinuous cubic 'gyroid' structure in a poly(ethylene -alt-propylene)-poly (dimethylsiloxane) diblock copolymer melt. The orientations of the micellar b.c.c. phases in the gels and the gyroid structure (belonging to the b.c.c. space group Ia (3) over bar d) following large-amplitude shearing are shown to be the same, i.e. directionally oriented crystals are produced in both cases, in which (111) directions are oriented along the shear direction.