Graft polymerization of acrylamide (AM) on the surface of crosslinked polyvinyl alcohol (CPVA) microspheres was realized by using ammonium cerium (Ⅳ) sulfate as initiator in an acidic aqueous solution (sulfuric acid)

resulting in the grafted microspheres CPVA-g-PAM.The effects of various factors on the graft polymerization reaction and the mechanism were emphatically studied.The experimental results show that by the oxidation action of Ce(Ⅳ) ion

free radicals can be produced on the surface of CPVA microspheres

on which there are a great deal of hydroxyl groups

and the radical graft polymerization of acrylamide (AM) can be favorably carried out.The grafting degree of PAM on CPVA-g-PAM microspheres is first decided by the acid concentration.The grafting degree initially increases with increasing the acid concentration

and then gradually decreases with the further increase of the acid concentration.As the concentration of H+ ion is 0.36 mol/L

the grafting degree has a maximum.The dependence of the grafting degree on the acid concentration reflects the special mechanism of the graft polymerization initiated by cerium salt.As the concentration of the initiator

ammonium cerium sulfate

is too great

the grafting degree will be decreased owing to the accelerating of the oxidation termination step

leading to the decrease of the grafting degree.The optimal concentration of cerium ammonium sulfate is 598×10-3 mol/L.During the graft polymerization process

the concentration of the monomer AM and the reaction temperature also affect the graft polymerization reaction to a certain extent.