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The combination of 13C solution NMR and 13C solid-state NMR (CP/MAS and MAS) is used to reveal the relative amount of rigid (crystalline) PVC in two PVC/DOP (50/50 wt % of poly(vinyl chloride)/di-2-ethylhexyl phthalate) samples with tacticities, α, of 0.52 and 0.575, respectively. For both samples the crystallinity decreases with increasing temperature, from about 30% at 90 °C to approximately 6% at 180 °C. By means of a careful spectral deconvolution of the 13C solid-state NMR spectra, the relative amounts of different triad sequences in the crystallites of PVC were obtained. The relative fractions of rr and rm sequences, about 0.5 and 0.4 respectively, are found to be constant as a function of temperatures above 90 °C. On the basis of proton low resolution T 2 experiments the mean average amorphous chain length between crystals was estimated at 50 monomer units at 160−180 °C. All results can be well understood by assuming the existence of crystallites which on average consist of only a few syndiotactic sequences in the chain direction.

A comprehensive SANS study on both rigid and plasticized suspension PVC demonstrates the presence of superstructural order in this polymer. Comparison of the experimental scattering invariant data with a tentative two-phase model points to specific penetration of the plasticizer in the noncrystalline regions of PVC. Thermal experiments manifest the gradual and thermoreversible melting of the crystalline regions at temperatures above 80-90 °C. Uniaxial deformation experiments on plasticized PVC confirm the existence of a heterogeneous network-structure in PVC where the crystalline tie-points act as physical cross-links. The observed anisotropic "butterfly" scattering pattern of a uniaxially stretched sample indicates the formation of concentration inhomogeneities as a consequence of the random distribution of the crystalline tie-points in plasticized PVC. The anistropy of the scattering pattern gradually disappears on heating, probably resulting from the increasing mobility of the plasticized interstitial medium.

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