Preparation of Poly(vinyl amine)-Grafted Crosslinked Poly(vinyl alcohol) Microspheres

摘要

Crosslinked poly(vinyl alcohol) (CPVA) microspheres were first prepared via the suspension polymerization of vinyl acetate and the alcoholysis of poly (vinyl acetate). Afterwards, a two-step method involving graft polymerization and Hofmann degradation was used to prepare functional poly(vinyl amine)-grafted crosslinked poly(vinyl alcohol) (PVAm-CPVA) microspheres, onto which poly(vinyl amine) (PVAm) macromolecules were grafted. The graft polymerization of acrylamide (AM) on CPVA microspheres was performed with cerium salt as the initiator in an acidic aqueous medium, resulting in polyacrylamide (PAM)-grafted CPVA microspheres. Subsequently, the grafted PAM was transformed into PVAm via the Hofmann degradation reaction, and PVAm-CPVA microspheres were prepared. The effects of the main factors on the graft polymerization and Hofmann degradation were examined, and the reaction mechanisms were researched in depth. The experimental results showed that for the graft polymerization of AM on CPVA microspheres initiated by cerium salt, the acid concentration and the amount of cerium salt affected the grafting degree of PAM greatly. For the Hofmann degradation reaction of the grafted PAM, the amination degree of PVAm-CPVA microspheres was obviously affected by the amount of sodium hypochlorite in the presence of sodium hydroxide. The preliminary adsorption tests showed that PVAm-CPVA microspheres were multifunctional and had strong adsorption ability for Fe(III) ions by chelation action and for chromate ions (CrO42-) by strong electrostatic interactions.