ON THE MESOMORPHIC FORM OF POLY(ETHYLENE-TEREPHTHALATE)

The conformation and the packing of poly(ethylene terephthalate) (PET) chains in the mesomorphic form have been investigated by accurate X-ray diffraction measurements, conformational energy analysis, and calculations of Fourier transforms of models. The X-ray diffraction pattern presented here is richer than those previously reported. In particular, besides the known meridional peaks at zeta = 1/c and 3/c, corresponding to a periodicity of 10.3 angstrom, a stronger meridional peak at zeta = 5/c has been shown. The reported Fourier transform calculations of isolated-chain models indicate that the experimental diffraction pattern of the mesomorphic form of PET can be qualitatively accounted for by extended linear chains obtained by random sequences of monomeric units in different minimum energy conformations. These random sequences of monomeric units generate chains in which any long-range correlation between the planes of the phenylene rings, along the chain, is absent.