Abstract
Crystallizable and noncrystallizable polymers were prepared from vinyl tert-butyl ether using Ziegler catalyst and stannic chloride as initiator respectively. Two types of polyvinyl tertbutyl ethers (PVtBE) were acetylated by means of acetic anhydride and stannic chloride or zinc chloride and then saponified to give polyvinyl alcohol.Two types of polyvinyl alcohol thus obtained were formylated using formic acid.From analytical results and infrared spectra studies on the products, it was shown that the formylation proceeded almost completely resulting to polyvinyl formates (PVF).
PVF derived from crystallizable PVtBE was crystallizable while PVF derived from noncrystallizable PVtBE was noncrystallizable.The crystallizable PVF gave sharp fiber diagram and the repeat distance along the fiber axis was 6.55Å showing that the regular sequences in the polymer possessed isotactic configuration.
Previously we found that PVF obtained by free radical polymerization at low temperature was crystallizable and supposed the existence of syndiotactic structure from the identity period-5.0Å.Thus isotactic and syndiotactic PVF are prepared and confirmed by x-ray examination for the first time.Syndiotactic propagation in the free radical polymerization of vinylesters is enhanced over isotactic propagation by decreasing polymerization by decreasing polymerization temperature.
Stretched films of isotactic and syndiotactic PVF were subjected to heterogeneous hydrolysis. Both polyvinyl alcohol films obtained gave fiber patterns which resemble each other and the identity period calculated was 2.5A in both samples.
