title: Synthesis and helical structures of poly(ω-alkynamide)s having chiral side chains: effect of solvent on their screw-sense inversion.
abstract: New ω-alkynamides, (S)-HC≡CCH2CONHCH2CH(CH3)CH2CH3 (1) and (S)-HC≡CCH2CH2CONHCH(CH3)CH2CH2CH2CH2CH3 (2) were synthesized and polymerized with a rhodium catalyst in CHCl3 to obtain cis-stereoregular poly(ω-alkynamide)s (poly(1) and poly(2)). Polarimetric, CD, and IR spectroscopic studies revealed that in solution the polymers adopted predominantly one-handed helical structures stabilized by intramolecular hydrogen bonds between the pendent amide groups. This behavior was similar to that of the corresponding poly(N-alkynylamide) counterparts (poly(3) and poly(4)) reported previously, whereas the helical senses were opposite to each other. The helical structures of the poly(ω-alkynamide)s were stable upon heating similar to those of the poly(N-alkynylamide)s, but the solvent response was completely different. An increase in MeOH content in CHCl3/MeOH resulted in inversion of the predominant screw-sense for poly(1) and poly(2). Conversely, poly(3) was transformed into a random coil, and poly(4) maintained the predominant screw-sense irrespective of MeOH content. The solvent dependence of predominant screw-sense for poly(1) and poly(2) was reasonably explained by molecular orbital studies using the conductor-like screening model (COSMO).
authors.affiliation: Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto 615-8510 (Japan).
authors.forename: Yuji
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Yu
authors.initials: Y
authors.lastname: Miyagi
authors.forename: Masashi
authors.initials: M
authors.lastname: Shiotsuki
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Inai
authors.forename: Toshio
authors.initials: T
authors.lastname: Masuda
authors.forename: Fumio
authors.initials: F
authors.lastname: Sanda
mesh_terms: D000480:Alkynes / Q000138:chemical synthesis / Q000737:chemistry*; D002384:Catalysis; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D009757:Nylons / Q000138:chemical synthesis* / Q000737:chemistry; D058105:Polymerization; D012238:Rhodium / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry
chemical_list: D000480:Alkynes; D009757:Nylons; D012997:Solvents; D012238:Rhodium
keywords: chirality; helical structures; hydrogen bonding; polymers; rhodium