Synthesis and Hierarchical Superstructures of Side-Chain Liquid Crystal Polyacetylenes Containing Galactopyranoside End-Groups

Abstract

Three kinds of chiral saccharide-containing liquid crystalline (LC) acetylenic monomers were prepared by click reaction between 2-azidoethyl-2,3,4,6-tetraacetyl-beta-D-galactopyranoside and 1-biphenylacetylene 4-alkynyloxybenzoate. The obtained monomers were polymerized by WCl(6)-Ph(4)Sn to form three side-chain LC polyacetylenes containing 1-[2-(2,3,4,6-tetraacetyl-beta-D-galactopyranos-1-yl)-ethyl]-1H-[1,2,3]-triazol-4'-biphenyl 4-alkynyloxybenzoate side groups. All monomers and polymers show a chiral smectic A phase. Self-assembled hiearchical superstructures of the chiral saccharide-containing LCs and LCPs in solution state were studied by field-emission scanning electron microscopy. Because of the LC behavior, the LC molecules exhibit a high segregation strength for phase separation in dilute solution (THF/H(2)O = 1:9 v/v). The self-assembled morphology of LC monomers was dependent upon the alkynyloxy chain length. Increasing the alkynyloxy chain length caused the self-assembled morphology to change from a platelet-like texture (LC-6) to helical twists morphology (LC-11 and LC-12). Furthermore, the helical twist morphological structure can be aligned on the polyimide rubbed glass substrate to form two-dimensional ordered helical patterns. In contrast to LC monomers, the LCP-11 self-assembled into much more complicate morphologies, including nanospheres and helical nanofibers. These nanofibers are evolved from the helical cables ornamented with entwining nanofibers upon natural evaporation of the solution in a mixture with a THF/methanol ratio of 3:7. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47:6596-6611, 2009