CHAIN CONFORMATION IN THE INDUCTION PERIOD OF CRYSTALLIZATION OF POLY(ETHYLENE-TEREPHTHALATE)

The change of chain conformation during the induction period of crystallization of poly(ethylene terephthalate) (PET) has been studied by means of a deuterium-labelling technique with small-angle neutron scattering. The scattering function of a single chain was analyzed based on the worm-like chain model. The stiffness of PET chains increased in the early stage of the induction period. According to the isotropic-nematic transition theory proposed by Doi et al., this increase of the chain stiffness induces the parallel ordering of polymer segments due to the excluded-volume effect. This orientational ordering may play an important role in the growth process of the density fluctuations observed in the induction period of crystallization.