Hydrogen bond network formation

The signs of the dynamic dichroism of the NH stretch and the amide I bands in nylons were found to be counterintuitive. Experiments show that polymer chains tend to align in the direction of an applied tensile strain. The CH stretching bands in nylons exhibit the expected negative dynamic dichroism indicating chain alignment in the strain direction. The Delta A' peaks for the NH and amide I bands are positive. The Delta A' peak for the NH band is also unusual in that it has a derivative shape. This can be explained by b and shifts brought about by anisotropic changes in the intermolecular spaci ng in the glassy polymer. Above T-g the derivative shape disappears but the Delta A' peak for both the NH and amide I absorption remain positive. We p ostulate that the positive Delta A' peaks of the NH and amide I bands resul t from a hydrogen bonding network where stress is transmitted through a net work consisting of covalent chains connected by hydrogen bonds.