Synthesis, helicity, and low infrared emissivity of optically active poly(N-propargylamide)s bearing stigmasteryl moieties

Abstract

Novel chiral N-propargylamide based on stigmasterol (M1, HCCCH2NHCOCH2CH2COO-R, R = stigmasteryl) and achiral N-propargylamide based on pivalic acid (M2) were prepared and (co)polymerized with rhodium zwitterions catalyst in CHCl3 to afford helical polyacetylenes with moderate molecular weights (8997–26777) in good yields. The polymers were characterized by Fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H NMR), gel permeation chromatography (GPC). Ultraviolet–visible spectroscopy (UV–Vis) and circular dichroism (CD) absorption spectra demonstrated that the as-prepared polymers could form helical structures with a preferential helicity. The formation of hydrogen bonds of poly(M1) in CHCl3 was investigated according to the solution sate IR spectroscopic data. The single-handed helical conformation and polymerization degree of the new-typed poly(N-propargylamide)s could be controlled by the changing the feed ratio of chiral and achiral monomers. Furthermore, the infrared emissivity values (0.536–0.798) of copolymers were investigated at 8–14 μm by the Infrared Emissometer.