CHARACTERIZATION OF POLY(VINYL ALCOHOL) DURING THE EMULSION POLYMERIZATION OF VINYL-ACETATE USING POLY(VINYL ALCOHOL) AS EMULSIFIER

During the emulsion polymerization of vinyl acetate (VAc) using poly(v inyl alcohol) (PVA) as stabilizer and potassium persulfate as initiato r, the VAc reacts with PVA forming PVA-graft-PVAc. When the grafted po lymer reaches a critical size it becomes water-insoluble and precipita tes from the aqueous phase contributing to the formation of polymer pa rticles. Since particle formation and therefore the properties of the final latex will depend on the degree of grafting, it is important to quantify and to characterize the grafted PVA. In this work, the quanti tative separation and characterization of the grafted water-insoluble PVA was carried out by a two-step selective solubilization of the PVAc latex, first with acetonitrile to separate PVAc homopolymer, followed by water to separate the water-soluble PVA from the remaining acetoni trile-insoluble material. After the separation, the water-soluble and water-insoluble PVA were characterized by Fourier Transform Infrared ( FTIR) spectroscopy and H-1 and C-13 nuclear magnetic resonance (NMR) a nalyses, from which the details of the PVA-graft-PVAc structure were o btained. (C) 1996 John Wiley & Sons, Inc.