Neutron scattering study of the shear induced behaviours of the smectic phase of a side chain liquid crystal polymers

We study the shear induced behaviour of a side-chain liquid crystal polymer, PA-OCH3, within the smectic (S-A) phase using small angle neutron scattering technique. We show that the formation of multilayer cylinders oriented along the velocity direction is a stable geometry which can be observed at different shear rates and temperatures in the S-A phase. A careful examination of the scattering intensities displayed on both ((z) over right arrow, (v) over right arrow) and ((v) over right arrow, <(<del>)over right arrow>v) planes indicates that the population of layers is higher along the neutral axis (z) over right arrow. The perpendicular orientation is thus more favoured than the parallel one. In the vicinity of the nematic (N)- S-A phase transition a shear induced S-A phase is observed, followed by a shear induced nematic phase reentrance at higher shear rates. A comparison with low molecular weight liquid crystals is carried out.