Poly(N-propargylamide)s bearing cholesteryl moieties: Preparation and optical activity

We synthesized a novel chiral cholesteryl-based N-propargylamide (Mch, HCCCH2NHCOCH2CH2COOch, ch = cholesteryl) from which homopolymers [P(Mch)] with different molecular weights (number-average molecular weight: 8600, 14100 and 30000) were prepared. The polymers formed helical structures with a preferential helicity. The three polymers increased in both helix content and specific rotation as the molecular weight increased. P(Mch)-8600 was studied in detail as the model polymer. P(Mch)-8600 adopted helical conformations in toluene, THF, CHCl3 and CH2Cl2, exhibited thermal stability with a decomposition temperature of 273 °C and formed a lyotropic liquid crystal under the studied conditions. Copolymers of different compositions of Mch and an achiral monomer (Met) were prepared. The copolymers formed helices to different degrees depending on the specific composition, indicating an effective approach for controlling the formation of helices in synthetic helical polymers.