Stereoregularity of PVC studied by ¹³C NMR

Abstract

SynopsisThe proton decoupled 13C NMR spectra of PVC polymerized at various temperatures were obtained using a 150-MHz NMR spectrometer. Chemical shift changes induced by a solvent effect were utilized to allow the detection of the six possible tetrads. Eight of ten possible pentads were also observed. The relative areas of tetrads and triads indicate that the polymerization of PVC above -2O' C is Bernoullian.

Absolute tacticity assignments of poly(vinyl chloride) via the two-dimensional NMR spin-lock RELAY experiment

“…The mrm and mmr tetrads are reversed from previous assignments in a similar solvent. 21,25 The tetrad assignments for the methylene carbon from region B can be easily projected vertically to region C and then correlated to the proton axis, giving the tetrad assignments for the methylene protons. Pentad assignments for the methine carbon in region D can be made by their unique communication to the tetrad assignments of region C (Figure 7).…”

Correlation between the tacticity and content of labile nondefect structures in poly(vinyl chloride)

“…The configuration and conformation of PVC in solution have been studied extensively with 1 H and 13 C NMR 7–14. However, the 13 C NMR spectra have shown some advantage over 1 H NMR spectra for determining triad and tetrad concentrations.…”

“…Besides, it is known that the distribution of the rotational conformations depends on the configuration, temperature, and nature of the solvent,15–18 and the overlapping of the resonance can be removed with the appropriate solvent. Usually, spectroscopic investigations of PVC are performed in chlorinated benzenes, that is, o ‐dichlorobenzene and 1,2,4‐trichlorobenzene, at temperatures near the thermal decomposition of the polymer 8, 9, 13–19. However, Elgert et al20 found it possible to observe all possible configurational pentad sequences at a lower temperature with dioxane (DI) as a solvent.…”