Properties of highly syndiotactic poly(vinyl alcohol)

The physical properties of a highly syndiotactic poly(vinyl alcohol) (PVA, diad syndiotacticity (r)=69%) and a commercial, atactic PVA (r=54%) were examined. The highly syndiotactic PVA was derived from poly (vinyl acetate) prepared through the radical polymerization of vinyl acetate in (CF3)2CHOH. The solubility, gelation behavior, melting point, and crystallization rate were drastically affected by the tacticity of the main chain. Some of the properties were measured using fiber samples prepared by the gel spinning technique. The fiber obtained from the syndiotactic PVA had a melting point of 274°C. This is the highest melting point reported for PVA. These effects of tacticity on the polymer properties are ascribed to the difference in intermolecular and/or intramolecular hydrogen bonding. A polymer chain with higher r content may form more regular and therefore more rigid hydrogen bonding between the polymer chains in the bulk sample. Such a detailed study on the effects of tacticity on the properties of PVA has not been reported so far.