Molecular Aggregation in Amorphous Polymers

Abstract

Abstract We have already established the existence of two types of packing of the links of neighboring molecular chains in amorphous rubber. The association of the links whose packing is characterized by a relatively dense distribution, similar to the packing of the molecules in low-molecular liquids, constitutes the liquid phase of amorphous rubber. In an x-ray diffraction diagram, this phase of the rubber shows an outer interference maximum caused by the intermolecular interference of the x-ray radiation which is coherently scattered by the adjacent links and corresponds to the average intermolecular spacing. Another phase of amorphous rubber, formed by the association of the segments of adjacent molecular chains, of quite disordered distribution, was called the gaseous phase. The links of the molecular chains which make up this phase of the rubber, because of their irregular distribution, scatter x-rays and show no intermolecular interference effect, so the scattering is like that in molecular gases. The dense background usually observed in diffraction diagrams of rubber, the intensity of which increases in the region of small scattering angles, can be explained by the effect of the independent scattering of the disordered links of the molecular chains of the rubber. It has the nature of scattering by a gas. The presence of such a type of molecularly disordered gaseous component is a peculiarity of the aggregation of molecules in amorphous high-molecular substances. Its existence is shown by the x-ray diffraction diagrams of amorphous high-molecular substances, in which, in the absence of low-molecular liquids, a background of independent scattering is always observed, besides the outer interference maximum which corresponds to the intermolecular spacing. The intensity I of the scattered (monochromatic) x-rays at any angle is, according to the theories developed, determined by the sum of the scattering intensities of the gaseous (Ig) and liquid (Il) phases of the amorphous substance.