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Helical and random coil conformations of N ‐propargylamide polymer and copolymers
Author(s) -
Deng Jianping,
Chen Bo,
Zhang Zhigang,
Yang Wantai
Publication year - 2007
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.2267
Subject(s) - comonomer , copolymer , monomer , polymer chemistry , polymer , materials science , random coil , polymerization , helix (gastropod) , tetrahydrofuran , solubility , crystallography , chemistry , circular dichroism , organic chemistry , ecology , solvent , snail , composite material , biology
An N ‐propargylamide monomer, CHCCH 2 NHCOC(CH 3 ) 2 CH 2 CH 3 (monomer 9), was polymerized in the presence of (nbd)Rh + B − (C 6 H 5 ) 4 (nbd represents norbornadiene) in CH 2 Cl 2 , CHCl 3 , tetrahydrofuran or dimethylformamide, to provide polymers with moderate number‐average molecular weights ( M n = 8700–12 100 g mol −1 ) in high yields (≥92%). The resulting poly( N ‐propargylamide) (polymer 9) dissolves almost completely in CHCl 3 (>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 CHCCH 2 NHCO(CH 2 ) 3 CH 3 (monomer 4) or CHCCH 2 NHCO(CH 2 ) 7 CH 3 (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