Elucidation of the fine structure of poly(vinyl chloride) by hydrogenation and 13C‐NMR analysis of low molecular weight fractions

Abstract

The following experiment was performed based on the assumption that the characteristic structural features of high molecular weight poly(vinyl chloride) (PVC) should be present to the same extent in its low molecular weight fractions. Two PVC fractions of molecular weight, 1500 and 800, respectively, (0.14% of total polymer) were isolated from bulk PVC (M_n 32,000) by extraction with methanol. This extract was transformed into paraffins by a new hydrogenation method using an excess of Raney nickel in order to facilitate identification. ¹³C‐NMR spectral data of the paraffins showed that almost 2 out of 1000 carbon atoms were linked to a side chain with more than five carbon atoms, and 5 out of 1000 carbon atoms were methyl branched. Gas chromatography‐mass spectrometry (GC–MS) analyses confirmed that the low molecular weight paraffins consisted of a sequence of even‐numbered homologs. These findings suggest indirectly that the surprisingly low degradation temperature of PVC is due to the arrangement of the chlorine atoms rather than to the branching of the alkyl chain.