Macromolecules, Vol.39, No.9, 3377-3385, 2006
Observation of nematic texture in a diblock copolymer melt
We have observed nematic textures in polarized optical microscopy and "plus" (+) patterns in depolarized light scattering (four lobes parallel to polarizer/analyzer axes) from a deeply quenched diblock copolymer melt with a cylindrical microstructure. Both of these features are similar to those found in nematic liquid crystalline polymers. In contrast, this same polymer sample exhibits a more conventional grain structure at shallower quench depths, characterized by an "X" pattern in depolarized light scattering (lobes at 45 degrees to polarized analyzer axes). A theoretical model is used to analyze the "plus" scattering patterns obtained from nematic textures in the single scattering limit. This model is used to quantify the nature of local correlations in our deeply quenched block copolymer melt. We show that the nematic texture is easy to align by shear flow while the granular structure is not.