Shear-induced ordering, block copolymers

As discussed below, the quality of the alignment (and even its direction in the case of lamellar morphology), is influenced by temperature, as well as the frequency and strain amplitude of the aligning shear field. No general theory for the alignment of block-copolymer phases has yet been developed. However, studies of a number of different block-copolymer systems show that in ordered states with cylindrical domains, shear orients the cylinders parallel to the flow, while for lamallar microdomains, two different shear-induced orientations are commonly found, depending on alignment conditions in both of these orientations, the flow direction lies in the plane of the lamellae. 

Simultaneous measurements together with small-angle X-ray or neutron scattering were performed for more than ten years, as exemplified by the studies of Okamoto et al. [146,147] and those of Bates et al. [148]. The latter examined the influence of mechanical deformation on the melt-phase behaviour of a block copolymer poly(ethylene-propylene)-6/ocA -poly(ethylethylene) (PEP-PEE), which contains 77 vol. % PEP with an overall molecular weight of 1.0 x 10 and a molecular-weight distribution with Mw/Mn = 1.07. The order-disorder transition (ODT) temperature was increased by shear deformation in the weak segregation regime, i.e. the microphase separation was induced by the... 

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