Polyacetylenes bearing mesogenic side groups: Synthesis and properties, 1 - Mesogenic substituents with a short flexible spacer

We report on the synthesis and polymerization of novel acetylenic monomers derived from 3-butyn-1-ol and bearing different potentially mesogenic substituents. Polymerization is carried out in solution with typical metathesis catalysts based on Mo and W and yields polyacetylenes with fairly high molecular weight and soluble in common organic solvents. Polymers are fully characterized by the point of view of the molecular structure, by GPC, FT-IR, NMR and UV/VIS techniques, and of the thermal and morphological behavior, by TGA, DSC, POM and X-ray diffraction experiments. Polymers with different amounts of cis and trans units are obtained, depending upon polymerization conditions. Although the monomers do not show any liquid crystalline behavior, polymers P2 and P3, containing in the side-chain respectively biphenyl and benzoyloxy benzoate as mesogenic cores, exhibit an enantiotropic smectic phase.