Helical and random coil conformations of N‐propargylamide polymer and copolymers |
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| Authors: | Jianping Deng Bo Chen Zhigang Zhang Wantai Yang |
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| Affiliation: | 1. State Key Laboratory of Chemical Resource Engineering, Beijing 100029, China;2. and College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China;3. From Hebei Normal University of Science and Technology, Hebei, Qinhuangdao 066004, China.;4. and College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, ChinaCollege of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China. |
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| Abstract: | An N‐propargylamide monomer, CH?CCH2NHCOC(CH3)2CH2CH3 (monomer 9), was polymerized in the presence of (nbd)Rh+B?(C6H5)4 (nbd represents norbornadiene) in CH2Cl2, CHCl3, tetrahydrofuran or dimethylformamide, to provide polymers with moderate number‐average molecular weights (Mn = 8700–12 100 g mol?1) in high yields (≥92%). The resulting poly(N‐propargylamide) (polymer 9) dissolves almost completely in CHCl3 (>95%). According to the UV‐visible spectra, measured at various temperatures, polymer 9 forms relatively stable helices over a wide temperature range (35–65 °C). Moreover, it exhibits reversible conformational transitions from an ordered helix to a random coil. On copolymerization of monomer 9 with CH?CCH2NHCO(CH2)3CH3 (monomer 4) or CH?CCH2NHCO(CH2)7CH3 (monomer 8), the solubility of polymer 9 improves noticeably. All the copolymers form helices under the experimental conditions. From the viewpoint of monomers 4 and 8, copolymerization with monomer 9 is favorable in terms of the copolymers forming helices. These findings reveal that the helical content and thermodynamic stability of the helices formed in the copolymers are likely to be controlled by selecting a suitable comonomer and by adjusting the composition of the copolymer. Copyright © 2007 Society of Chemical Industry |
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| Keywords: | helical conformation random coil N‐propargylamide rhodium‐based catalyst |
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