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 commerc ial rheometer with a shear sandwich geometry in which the sample is subject ed to a planar oscillatory deformation. This instrument has been used for t ime-resolved small-angle X-ray scattering/rheology experiments at the Synch rotron 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 solution s, and on the bicontinuous cubic phase of a block copolymer melt. Represent ative results are presented for face-centred cubic (f.c.c.) and body centre d cubic (b.c.c.) phases in gels of poly(oxyethylene)-poly(oxybutylene) dibl ock copolymers, and for the bicontinuous cubic 'gyroid' structure in a poly (ethylene -alt-propylene)-poly (dimethylsiloxane) diblock copolymer melt. T he orientations of the micellar b.c.c. phases in the gels and the gyroid st ructure (belonging to the b.c.c. space group Ia (3) over bar d) following l arge-amplitude shearing are shown to be the same, i.e. directionally orient ed crystals are produced in both cases, in which (111) directions are orien ted along the shear direction.