Synthesis of high-molecular-weight poly(vinyl alcohol) with high yield by novel one-batch suspension polymerization of vinyl acetate and saponification

ABSTRACT:To prepare high molecular weight (HMW) poly(vinyl acetate) (PVAc) with high yield and high linearity as a precursor of HMW poly(vinyl alcohol) (PVA), vinyl acetate (VAc) was emulsion polymerized using, azo initiator, 2,2Ј-azobis(2-amidinopropane) dihydrochloride (AAPH). This was compared with the polymerization using potassium peroxodisulfate (KPS) as an initiator at various polymerization conditions. PVA, having a maximum number average degree of polymerization (P n ) of 3500 was obtained by the saponification of PVAc with P n of 13,000 -14,000, degree of branching (DB) for the acetyl group of about 3.4 -3.5, and a maximum conversion of VAc into PVAc of 95%, which was polymerized by AAPH. These numerical values were superior compared with 14,500 -15,000 of P n of PVAc, obtained by KPS, and 3100 of maximum P n of resulting PVA, DB of about 3.7-3.8, and maximum conversion of 90%. From the foregoing experimental results, we found that AAPH was a more efficient initiator than KPS in increasing both conversion of PVAc and molecular weight of PVA. In addition, PVAc microspheres, obtained by these emulsion polymerizations, can be converted to PVA / PVAc shell / core microspheres through a series of surface-saponifications, maintaining their spherical morphology. Various surface morphologies, such as flat or wrinkled and swellable or nonswellable ones formed by the various molecular parameters and saponification conditions, were examined.

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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)

Lyoo

Song

Lee

et al. 2006

J of Applied Polymer Sci

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Vinyl acetate (VAc) was solution-polymerized at 408C and 508C using 4,4 0 -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 n ) of 4300 could be prepared by the saponification of PVAc having maximum P n of 7900 polymerized using ACVA concentration of 2 Â 10 À5 mol/mol of VAc at 408C. Moreover, low DB of below 1 could be obtained in ACVA system, nevertheless of general polymerization temperatures of 408C and 508C. This suggests an easy way for producing HMW PVA with high yield by conventional solution polymerization without using special methods such as low-temperature cooling or irradiation.

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Synthesis of high-molecular-weight poly(vinyl alcohol) with high yield by novel one-batch suspension polymerization of vinyl acetate and saponification

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Bioadhesive Polymers for Drug Delivery

Bioadhesive Polymers for Drug Delivery

Preparation of high molecular weight poly(vinyl alcohol) with high yield by emulsion polymerization of vinyl acetate using 2,2′‐azobis(2‐amidinopropane) dihydrochloride

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)

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