Neutron structure analysis of poly(vinyl alcohol)

Different crystal structure models have been proposed for atactic poly(vinyl alcohol) by two groups: Bunn and Sakurada et al. The models differ principally in the azimuthal angle of the planar zigzag backbone and the hydrogen bonding network. In the present study, reexamination of the crystal structure analysis was carried out by using both the X-ray and neutron diffraction methods. The crystal structure model proposed by Bunn is found to be superior. The (Fo − Fc) synthesis was made for the neutron data (100 K), in which the hydrogen atoms to be associated with the hydrogen bonds are not incorporated into Fc calculation. On the map, three peaks were found, which may be attributed to the hydrogen atoms to be associated with the intramolecular hydrogen bonds between OH groups in an isotactic sequence and the two kinds of intermolecular hydrogen bonds.