Segmental density distribution of linear amorphous polymer molecules

In light of the inability of the Gaussian segmental distribution with its resultant deep intermolecular entanglements to explain satisfactorily a number of phenomena, a new segmental density model is proposed. This model, a uniform distribution of segmental density through molecular domains, limits intermolecular interactions mostly to the domains' surfaces. The model thus predicts that zero shear viscosity and maximum relaxation time follow the same molecular weight dependence, being dependent on M (or N) at low weights and on M3.5 (up to M4.5) at high molecular weights with a smooth transition over a fourfold increase in the molecular weight. The crystallization of crystallizable polymers and the existence of amorphous nodules are explained on the basis of minor ordering within molecular domains and the subsequent agglomeration of the latter to nodules or nuclei in order to minimize their “surface” energy. Experimental data from the literature are shown to agree with the predicted behavior. Other phenomena, such as the independence of heat of mixing from M, some solution properties, flow properties of polyvinyl chloride, and intermolecular graft cross-linking, are briefly dealt with and the data explained on the basis of the uniform density model.