Properties of highly syndiotactic poly(vinyl alcohol)

The physical proper-ties of a highly syndiotactic poly(vinyl alcohol) (PVA, diad syndiotacticity (r) = 69%) and a commercial, atactic PVA (r = 54%) we re examined. The highly syndiotactic PVA was derived from poly (vinyl aceta te) prepared through the radical polymerization of vinyl acetate in (CF3)(2 )CHOH. The solubility, gelation behavior, melting point, and crystallizatio n rate were drastically affected by the tacticity of the main chain. Some o f the properties were measured using fiber samples prepared by the gel spin ning technique. The fiber obtained from the syndiotactic PVA had a melting point of 274 degreesC. This is the highest melting point reported for PVA. These effects of tacticity on the polymer properties are ascribed to the di fference in intermolecular and/or intramolecular hydrogen bonding. A polyme r chain with higher r content may form more regular and therefore more rigi d hydrogen bonding between the polymer chains in the bulk sample. Such a de tailed study on the effects of tacticity on the properties of PVA has not b een reported so far. (C) 2001 Elsevier Science Ltd. All rights reserved.