Deformation mechanisms of constrained polymer chains. I. Geometrically induced correlations in the deformation response mechanisms of tie molecules

The geometrical constraints acting on sections of tie molecules in noncrystalline regions severely limit the number and type of available polymer chain conformations. It is shown that these constraints induce explicit correlations in the rotations about the backbone bonds. These correlated rotations, in turn, specify distinct structural conversion paths which define the molecular mechanisms underlying the deformation response of tie molecules. Application of these constraining relationships to highly oriented polyethylene shows that the kink and jog structures of tie molecules can be decomposed into combinations of three primary conformational building blocks. Each of the basic conformational subunits follow an explicit set of dihedral angle correlations and, consequently, imparts specific characteristics to the composite structure of tie molecules. It is proposed that the composite response characteristics of tie molecules can be described as linear combinations of the response characteristics of these three primary conformational subunits.