Molecular Structures and Functional Modifications of Poly(vinyl Alcohol) by Tohei Moritani

Poly(vinyl alcohol) (a), its partially hydrolyzed product or poly(vinyl alcohol-co-vinyl acetate) (b) and poly(ethylene-co-vinyl alcohol) (c) are all industrially significant polymers used mainly for fiber and film, size and emulsifier/stabilizer, and gas-barrier material, respectively. In this thesis, these vinyl alcohol-based polymers have been discussed from two aspects: the molecular structures characterized by high resolution nuclear magnetic resonance spectroscopy (NMR) and functional modifications with ionic or crosslinkable groups by copolymerization. Tacticity and Sequence Distribution The quantitative determination of tacticity for poly(vinyl alcohol) has been difficult using IR and 1H-NMR before the present work because of severe overlapping of spectral lines. No attention has been paid to the hydroxyl proton of the polymer in 1H-NMR because it can not be observed due to rapid exchange with water used as a usual solvent. In the present work it has been found that the hydroxyl proton can be observed as three well-separated lines assigned to the three triad sequences of tacticity when dimethyl sulfoxide is used as another solvent instead of water. This discovery has made it possible to determine the tacticity of the polymer easily and quantitatively. To determine how acetyl group distributes along molecular chains for partially hydrolyzed products is also significant but no analytical method has been known so far.