Mesophase Structure of Low-Wetting Liquid Crystalline Polyacrylates with New Perfluoroalkyl Benzoate Side Groups

The synthesis, thermal behavior, bulk microstructure and wettability of new polyacrylates carrying spaced 4-perfluorohexylpropyl benzoate and 4-perfluorooctylpropyl benzoate units in the side groups were investigated. X-ray diffraction analysis proved the formation of different smectic mesophases (SmI2, SmF2, SmC2) and the evolution of their structures and lattice parameters with temperature. The mesophase polymorphic behavior depended on the length of the perfluorinated chain segment in the repeat unit. The electron density profiles along the smectic layer normal were drawn and provided a deeper insight into the packing of the side chains in a tilted, double layer structure. Thin polymer films were cast from solution, and their low wettability was established by measurements of contact angles with different probing liquids. We suggest that the hydrophobicity and lipophobicity of the films are enhanced by the mesophase surface structure which is mediated by the high-order, mesophase bulk structure.