Conformations of Macromolecules in Condensed Phases

Evidence demonstrating that configurations of polymers in the amorphous state are unperturbed by intermolecular interactions with neighboring chains is reviewed, with particular emphasis on recent results of neutron scattering by mixtures of deuterated and protonated species. Extension of this technique to larger angles than those required for determination of the radius of gryration establishes close agreement between intersegnnt correlations in a polymer chain in the amorphous state and those within the isolated chain, even at distances as small as bA. Neutron scattering studies have been especially useful in discern— ing the nature of the molecular morphology at the crystal—amorphous interface. In both polyethylene and isotactic polypropylene, adjacent re—entry is comparatively rare, contrary to models accepted in the past. Return of a given chain to a site of the crystal surface somewhat removed from its point of exit must occur frequen— tly, however. These findings have important implications regarding the process of plastic deformation in seinicrystalline polynrs. Recent studies by Wignall and Wu confirm that local nlting of small crystalline regions effectuates the process.