Intramolecular hydrogen bonding among the side-chain amide groups in isotactic poly[(S)-1-(1-naphthyl)-ethyl methacrylamide] (1) and poly[(S)-1-phenylethyl methacrylamide] (2) were examined in films cast from 1,2-dichloroethane (EDC). Curve fitting of the amide I band shows that the peaks for the full hydrogen bonds are broader as compared with those in EDC solution, suggesting that the hydrogen bonds formed in film are looser and less extensive than those in solution. X-Ray diffraction (XRD) measurements show that these polymers give hexagonal-like aggregates in film, indicating that they form rod-like helical structures as suggested by molecular mechanics calculations. Isotactic 2 film shows a positive circular dichroic (CD) peak at ca. 230 nm, characteristic of the fully hydrogen-bonded helical structure, which disappears upon annealing. Isotactic 1 film shows two CD positive peaks at ca. 210 nm and at ca. 230 nm, their relative intensities changing upon annealing, which together with the CD measurements in solution suggests that the hydrogen-bonded and non-hydrogen bonded structures of isotactic 1 give, in the 1Bb band of the naphthyl group, exciton coupling of positive chirality and that of negative chirality, respectively, the overall CD being determined by their relative contents.
All Science Journal Classification (ASJC) codes
- Polymers and Plastics
- Materials Chemistry