Textures and defects of the hexagonal columnar phase of phthalocyaninato-poly(siloxane) derivatives (PCPS)

Samples of alkyloxy derivatives of phthalocyaninato-poly(siloxane) (PCPS) with various patterns of substitution were prepared by solution casting. After this history of treatment they form lyotropic hexagonal columnar mesophases. Textures and defects were analyzed in the “frozen” state (with the solvent evaporated) by optical and electron microscopy. With the exception of the space occupied by a single molecule, significant differences of the behavior in the liquid crystalline state were not found among the PCPS derivatives. The side chains of the samples under investigation are too short to be ordered but in the frozen liquid crystalline state the main chains are in register. Both optical and electron microscopy provide evidence for undulations of the molecular trajectories with preferential orientation. Defects typical of hexagonal columnar phases, e.g. walls of various origin and developable domains, where observed. Together with the undulations, transversal edge dislocations occur, as can be demonstrated by high resolution electron microscopy. Inserted lattice half-planes enable the system to minimize the elastic energy of the highly persistent molecules in the bent director field.