Structure and properties of syndiotacticity-rich poly(vinyl alcohol) prepared through saponification of drawn poly(vinyl trifluoroacetate) with gaseous ammonia

The structure and properties of syndiotacticity-rich poly(vinyl alcohol) (s -PVA) prepared through the saponification of drawn poly(vinyl trifluoroacet ate) (PVTFAc) with gaseous ammonia were studied. The PVTFAc samples with s- diad % of 59 and 64 were used. The s-PVAs had low densities and showed X-ra y diagrams similar to the fiber diagram of PVA with indistinct 100, 101, 10 1, and 200 plane reflections and without the plane reflections seen at the equator of a typical fiber diagram, such as 001, 201, and 002. The s-PVAs h ad melting points comparable to those of saponified and heat-drawn samples, indicating a PVA with the typical fiber structure as seen in the X-ray dia gram of a sample. The intensity of the 916 cm(-1) band in the infrared spec trum related to syndiotactic diads decreased with drawing, suggesting an in crease in the crystallinity. Crystals with more defects are thought to be p roduced in saponification. The s-PVA films drawn 16 times and saponified ha d a Young's modulus and strength at break of 22 and 1.5 GPa for the sample from S-59 and 14 and 1.2 GPa for the sample from S-64, respectively. The cr ystallization-sensitive band of 1145 cm(-1) in the infrared spectra of the saponified samples was weak. (C) 2001 John Wiley & Sons, Inc.