Synthesis and crosslinking of vinyl-terminated biphenyl and naphthalene liquid-crystalline poly(epichlorohydrin) derivatives:: Effect of nonmesogenic nonvinylic units on the mesogenic properties

Two series of vinyl-terminated side-chain liquid-crystalline polyethers containing ethylene oxide or glycidyl aromatic carboxylates as spacers were synthesized. The mesogenic cores were 4,4'-biphenyl or 2,6-naphthalene moieties. The polymers were synthesized by chemically modifying poly(epichlorohydrin) or poly(epichlorohydrin)-poly(ethylene oxide) with the corresponding mesogenic carboxylic acids or with mixtures of these acids and the nonmesogenic non-crosslinkable analogous 4-biphenyl- and 2-naphthalenecarboxylic acids. In most cases the degree of modification achieved was higher than 90%. The polymers were characterized by chlorine analysis, IR, and H-1 and C-13 NMR spectroscopies; viscosimetry; size exclusion chromatography; multi-angle laser light scattering; and thermogravimetric analysis. The liquid-crystal behavior, shown by most polymers, was examined by differential scanning calorimetry, polarized optical microscopy (POM), and X-ray diffraction on mechanically oriented samples. The crosslinking of most polymers was done by peroxide-type initiators that led to liquid-crystal thermosets or elastomers. The freezing of the mesophase organization on the crosslinked materials was confirmed by POM and X-ray diffraction. (C) 2002 Wiley Periodicals, Inc.