Water stability of high-molecular-weight (HMW) syndiotacticity-rich poly(vinyl alcohol) (PVA)/HMW atactic PVA/Iodine complex blend films

To precisely identify the effect of blend ratios of syndiotacticity-rich poly(vinyl alcohol) (s-PVA)/atactic PVA (a-PVA) on the water stability of s-PVA/a-PVA/iodine complex blend films, we prepared two PVAs with similar number-averaged degrees of polymerization of 4000 and degrees of saponification of 99.9% and with different syndiotactic diad contents of 58.5 and 53.5%, respectively. The desorption behavior of iodine in s-PVA/a-PVA/iodine complex films in water was investigated in terms of the solubility of s-PVA/a-PVA blend films in water. The degree of solubility of s-PVA/a-PVA blend films with s-PVA content over 50% in water at 70°C was limited to about 10-20%, whereas that of s-PVA/a-PVA blend films with s-PVA con tent of 10% was 85% under the same conditions. The degree of iodine desorption of complex blend films decreased with increasing s-PVA content. The degree of iodine desorption of s-PVA/a-PVA drawn film with s-PVA content of 90% was limited to 7%, regardless of the soaking temperature from 30 to 70°C. The desorption of iodine in water was strongly affected by the dissolution of blends. Moreover, the stability of iodine in the drawn s-PVA/ a-PVA/iodine blend films in hot water was far superior to that of the undrawn film.