SAXS study of the swelling and shear orientation of the lamellar phase formed by a diblock copolymer

The swelling of the lamellar phase of a diblock copolymer, E18B10, has been studied using small-angle X-ray scattering (SAXS). Deviations from the expected swelling law for constant thickness bilayers are ascribed to the formation of pore defects in the lamellar phase (so-called ‘mesh’ phase), as temperature is increased. This is supported by deuterium NMR data for the diblock in D2O, which indicate well-ordered lamellae at low temperature, but increasing fractions of mobile D2O at high temperature. The orientation of the lamellar phase under steady shear is studied via SAXS. At high shear rates, the lamellae are predominantly oriented with their normals along the neutral direction (perpendicular orientation). At lower shear rates, the unfavourable orientation with lamellar normals along the shear direction is observed as a transient state.