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Poly(phenylacetylene)s and poly(1-alkyne)s containing chiral sterol pendant groups with molecular structures of
-[HC=C-C6H4-CO2-R]n-, -[HC=C-C6H4-O(CH2)10-CO2-R]n- and -[HC=C(CH2) mCO2-R]n-, (where R =
cholesterol, stigmasterol, ergosterol and m = 2, 3, 8} are designed and synthesized. The monomers are prepared by esterifications of acetylenic acids with cholesterol, stigmasterol, and ergosterol and exhibit cholestericity at high
temperatures. Polymerizations of the monomers are effected by WCl6-Ph4Sn, MoCl5-Ph4Sn, and organorhodium
catalysts, giving high molecular weight (Mw up to 8.0 × 105) polymers in high yields (up to 99%). The structures and
properties of the polymers are characterized and evaluated by IR, NMR, TGA, DSC, POM, X-ray, UV, and CD
analyses. All the polymers are thermally stable (greater than or equal to 300 °C). Polymers with long flexible alkyl chains form smectic and
cholesteric phases at elevated temperatures. With an increase in the spacer length in poly(1-alkyne)s, the packing
arrangements of the mesogenic pendants in the mesophases change from bilayer or mixed mono- and bilayer into
homogeneous monolayer structures. Few poly(phenylacetylene)s show CD bands in the absorption region of the
polyacetylene backbones, revealing that the main chains are helically rotating with a preferred screw sense.
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