Synthesis of high molecular weight poly(vinyl alcohol) by low temperature polymerization of vinyl acetate in tertiary butyl alcohol and the following saponification

Vinyl acetate (VAc) was polymerized at 30, 40 and 50 degrees C using 2,2' -azobis (2,4-dimethylvaleronitrile) (ADMVN) and tertiary butyl alcohol(TBA) as the initiator and the solvent, respectively. High molecular weight (HMW) atactic poly(vinyl alcohol) (PVA) was prepared by saponifying the poly(vinyl acetate) (PVAc) synthesized. The effect of polymerization conditions were investigated in terms of conversion, degree of branching for acetyl group of PVAc, and molecular weight of both PVAc and PVA. The polymerization rate of VAc in TEA was proportional to the 0.49th power of ADMVN concentration in good accordance with the theoretical value of 0.5. HMW-PVA with high yield could be obtained successfully, probably due to lower polymerization temperature and decreased chain transfer reaction rate which was achieved by adapting ADMVN and TEA. PVAc having average degree of polymerization (P-n) of 10000 similar to 13000 was obtained at the conversion of 35 similar to 70%. Saponification of so prepared PVAc yielded PVA having P-n of 2400 similar to 6100. The syndiotactic diad content increased with decreasing polymerization temperature and increasing VAc concentration due to a steric hindrance effect of TEA during polymerization.