New type of temperature variation of X-ray diffraction from a number of polymers

Abstract

In contrast to the intensity reduction of X-ray reflexes normally observed on increasing the temperature of the polymers examined with an increase in temperature, both the intensity I and the integral intensity P of the main diffraction maximum, characterizing the inter-chain distance in the structure of these polymers, increase. Temperature variations of intensity are fully reversible. An increase in X-ray reflex intensity with an increase in temperature may be the result of thermal expansion, in which electron density of the main part of the macromolecule remains unchanged, but electron density in the boundary zone of intermolecular contacts decreases. These changes increase the intensity of the intermolecular diffraction maximum. A reversible increase in the intensity of diffraction maxima with an increase in temperature may be observed with fair thermal expansion using polymers with a large diameter of macromolecules ( ∼ 10–15 A ̊ ).