Neutron Scattering Studies on the Crystallization of Polymers

Abstract

Abstract Neutron scattering on mixtures of deuterated and undeuterated molecules offer a new approach for solving long standing problems of the structure of semicrystalline polymers. The various ranges of the amount of the scattering vector q yield different informations. From small angle studies the radius of gyration Rg can be obtained, which does not change markedly by crystallization. The scattering intensity in “the intermediate angle range yields mainly the average distance of the crystalline stems. Experimental results show that not only Rg remains almost constant, but that also the pair distribution function g(r) of the monomer units for r«Rg does not change appreciably during crystallization, since the average distance is controlled by the inherent statistical properties of the chain. There is no indication of privileged adjacent re-entry for melt crystallized polymers. The problems of “intramolecular clustering” due to crystallization can be treated by an Ornstein-Zernike approach. The direct correlation function c(x) is related to the pseudopotential of the interaction between the crystalline stems, which is caused by the amorphous loops. The intermolecular clustering can be described in a similar way, it leads to an enhancement of the intramolecular clustering.