Abstract:

In order to reduce or avoid the kisadvantages of solution polymerization, such as solvent post-treatment, acrylamide (AM) monomer was allowed to diffuse into polyvinyl alcohol (PVA) powder, along with a small amount of water as a carrier, and a graft copolymerization was simultaneously accompanied by diffusion of the monomer and initiator solution. As the precondition of the solid-state reaction, PVA powder was swollen enough by water so as to obtain larger free volume in PVA matrix. Then graft copolymerization of polyacrylamide (PAM) onto PVA occurred in solid-state under the condition initiated by ammonium persulfate and sodium bisulfite redox system. The grafting ratio was found to be as high as 61% in the solid-state graft copolymerization at the condition of PVA 50g with AM 35g at a temperature of 40 °C for 120 min, initiated by 0.02g of (NH4)2S2O8 and 0.01g of NaHSO3. Before the reaction, the PVA powder was swelled at 40 °C for 120 min with small amount of water. Fourier transform infrared spectroscopy, X-ray diffraction and differential scanning calorimetry were used for the analyses of the structure of the product, polyvinyl(alcohol)-graft-polyacrylamide (PVA-g-PAM). A plausible mechanism of grafting has been suggested. The influences of reaction factors such as temperature, reaction time, the amounts of acrylamide monomer and initiator were discussed, based on the grafting parameters including grafting ratio and grafting efficiency.

Key words: solid-state, graft copolymerization, polyvinvl alcohol, acrylamide, redox system initiation