Effects of side-chain structure and solvent on intramolecular hydrogen bonding in isotactic poly(methacrylamide)s

Intramolecular hydrogen bonding in isotactic poly(methacrylamide)s, i.e., p oly[(S)-1-phenylethyl methacrylamide] (1) and isotactic poly[(S)-1-(1-napht hyl)ethyl methacrylamide] (2), was examined by IR,H- 1 NMR, and CD in non-h ydrogen bonding and hydrogen bonding solvents and in mixtures thereof Isota ctic 1 was found to form intramolecular hydrogen bonds more extensively tha n isotactic 2; the former even forms a stable hydrogen-bonded structure in a hydrogen bonding solvent, i.e., dioxane, suggesting that the phenyl group s as well as the methyl groups in the side chains provide adequate steric e ffects for stabilization of the hydrogen-bonded structure. Formation. in so lution, of helical structures of one prevailing handedness with specific ch romophore orientation is suggested. The hydrogen-bonded structures were fou nd to break down on addition of a helix-breaking solvent. trifluoroacetic a cid.