High-Field1H-NMR Study of Poly(Vinyl Chloride) Defects

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Abstract
Radical poly(vinyl chlorides), (PVC), obtained in bulk and in suspension polymerizations, and their low molecular weight extracts have been thoroughly studied by high-field NMR to obtain better qualitative and quantitative analyses of their structural defects. Assignments have been achieved by 1H-1H decoupling experiments and hyperfine spectral structure analysis of model compounds and low molecular weight extracts. Strong effects of the nature of the solvents used in 1H-NMR analysis were observed. Most of the defects of these radical PVC's have been quantitatively estimated in terms of average number values in correlation with their [Mbar]n. End-groups of type [I'] (= −CH2−CH[dbnd]CH[sbnd]CH2C1) are about 0.5 per chain; internal double bonds can only be estimated by difference, and their amount increases with increasing conversion. A very low quantity of vinyl chain end [I'] ([dbnd] [sbnd]CHC1[sbnd]CH[dbnd]CH2) has been found only in low molecular weight extracts. For the three probable saturated chloromethyl ends [II] ([dbnd][sbnd]CHCl[sbnd]CH2Cl), [III] ([dbnd] [sbnd]CH2[sbnd]CH2Cl), and [IV] ([dbnd] >CH[sbnd]CH2C1), only [II] and [III] were definitely identified. Finally, in taking into account all the endgroups, it has been concluded that branches would be grafted throughout the process. On the average, 4 to 5 branches have been found per chain of high molecular weight PVC.