STRUCTURAL IRREGULARITIES IN POLYVINYL-ALCOHOL)

In the reported investigation, PVA derived from the product of polymerization of vinyl acetate in methanol have been characterized by various physical and chemical methods before and after NaIO//4 cleavage. The 220-MHz **1H-NMR spectra confirm the reliability of NaIO//4 titrimetry for estimating 1,2-glycol content and help explain the tendency for viscometry to grossly underestimate the 1,2-glycol content for low molecular weight polymers. The spectra and related chemical evidence indicate that the major endgroups are HOCH//2CH//2 - and CH//3CH(OH)CH(OH)CH//2 - . beta -Hydroxyethyl groups also occur as short chain branches, mainly attached to alpha carbon atoms in the normal head-to-tail polymer chain sequence. The concentrations of the branch and endgroups depend on polymerization conditions and help explain polymerization ″solvent″ effects on physical properties.