Fluorinated mesogen-jacketed liquid-crystalline polymers as surface-modifying agents: Design, synthesis and characterization

Abstract

Monomers with semifluorinated tails on monomeric vinyl hydroquinone cores were synthesized and their polymerization behavior was examined. The resulting semifluorinated mesogen-jacketed liquid-crystalline polymers (MJLCPs) proved to form fairly hydrophobic surfaces with water contact angles of 110–118°. These polymers were studied for the role of the fluorinated groups on both liquid-crystalline (LC) behavior and surface properties. Initial surface stability studies showed that these fluorinated MJLCP surfaces are relatively more stable than comparable systems of side-chain fluorocarbon LC blocks. Our studies show that M(1), 2,5-bis[(10-perfluorohexyl-decanoyl)oxy]styrene, could not be homopolymerized, while M(2) incorporating benzoate groups, 2,5-bis[4-(10-perfluorohexyl-decanyloxy)benzyloxy]styrene, permitted facile homopolymerization and block copolymer preparation by stable free-radical polymerization. As determined by wide-angle X-ray diffraction, the SCN transition temperature of the block copolymer shifted to a higher temperature with an increase in the DP of M(2). NEXAFS studies showed no net orientation of the (CF2)n side chains towards the surface normal consistent with observed low order smectic phases, nevertheless pointed to the presence of fairly hydrophobic CF2-covered surfaces. The above evidence proved the materials are suitable for application as surface-modifying agents. Polarized optical micrograph of M(1) showing a mosaic texture due to a smectic mesophase obtained on slow cooling at 2 K min−1 from the isotropic phase.