Preparation of high-molecular-weight poly(vinyl alcohol) with high yield by solution polymerization of vinyl acetate in methanol using 4,4′-azobis(4-cyanovaleric acid)

Vinyl acetate (VAc) was solution-polymerized at 40 degrees C and 50 degrees C using 4,4'-azobis(4-cyanovaleric acid) (ACVA) as an initiator and methanol as a solvent, and effects of polymerization temperature and initiator concentration were investigated in terms of conversion of VAc into poly (vinyl acetate) (PVAc), degree of branching (DB) for acetyl group of PVAc, and molecular weights of PVAc and resulting poly(vinyl alcohol) (PVA) obtained by saponifying with sodium hydroxide. Slower polymerization rate by adopting ACVA and lower viscosity by methanol proved to be efficient in obtaining linear high-molecular-weight (HMW) PVAc with high conversion and HMW PVA. PVA having maximum number-average degree of polymerization (P,) of 4300 could be prepared by the saponification of PVAc having maximum P-n of 7900 polymerized using ACVA concentration of 2 x 10(-5) mol/mol of VAc at 40 degrees C. Moreover, low DB of below 1 could be obtained in ACVA system, nevertheless of general polymerization temperatures of 40 degrees C and 50 degrees C. This suggests an easy way for producing HMW PVA with high yield by conventional solution polymerization without using special methods such as tow-temperature cooling or irradiation. (c) 2006 Wiley Periodicals, Inc.