Study On Preparation And Properties Of Poly(acrylamide)/SiO₂ Nanocomposite Hydrogel

Due to the existence of hydrophilic groups in polymer chains, conventional hydrogels have good water-soluble ability, but the fragile nature after absorbing water limit its development. Organic/inorganic nanocomposite gels (NC gels) contanin the strength and thermostability of organic material and the functionality of organic polymer, so they can improve the comprehensive performance of gels, such as absorbing ability, heat resistance and strength. NC gels is the hot topic in hydrogel field, which can be widely used in medicine, health, agriculture, forestry, oilfield, gardening and environmental protection.In this paper, a series of poly(acrylamide)/silica nanocomposite hydrogels were novelly prepared via in situ free-radical polymerization using silica sol as an inorganic component, acrylamide (AM) as monomer, N,N'-methylenebisacrylamide (MBAM) as cross-linker, ammonium persulfate (APS) as initiator. The prepared nanocomposite hydrogels were of good transparence and no pores. The addition of silica sol was to bring silica nanoparticles to form organic (polymer)/inorganic system and the effect of silica sol content on the properties of PAM/ilica nanocomposite system were studied.The structures of the PAM/SiO2 nanocomposite hydrogels were characterized and analyzed by FITR, SEM and AFM. FTIR results indicated that during the cross-linking process of PAM, the C=C absorption peak disappeared and the amino bond brodened, which meant that the cross-linking reaction was completed and there might exist strong hydrogen bond interactions between Si-O with -NH. In other words, the surface of silica sol interacted with PAM by chemical interaction. The characterization of microscopic structure displayed that silica particles were of nano degree and in the monodisperse around the PAM network structure. This promoted high degree of attachment to the polymer chain and enhanced the interfacial interaction between these two components. The largest particle size is 68 nm and the dry PAM/SiO2 nanocomposite hydrogels were the porous structure. The effect of the content of silica sol and cross-linking agent on the swelling performance of NC gels were studied in detail. The ESR of nanocomposite hydrogels decreased dramatically with the increase of the silica sol content. The response results of NC gels to the pH value and the concentration of salt indicated that the swelling ratio of the NC gels with certain silica content increased with the increasing pH and the ESR in basic solution was larger. The nanocomposite structure increased the mechanical strength and thermo properties of PAM/SiO2 nanocomposite hydrogels. The strength of NC gels doubled and could reach 16.1KPa at the high content of water. The Tg of nanocomposite hydrogels has been srengthened in comparison to pure PAM and the residual sample was inorganic SiO2, which could be attributed to hydrogen bonding or other physical interactions between nanoparticals and PAM molecules. Rheological test showed that the gelation process of nanocomposite hydrogels had the dynamic characteristics and the gelling induction time becomes longer with the increasing content of silica sol.As a new material, PAM/SiO2 nanocomposite hydrogel has excellent properties of inorganic nanoparticles and polymer gel. Essential scientific datas and theoretical foundation for the feasibility of the PAM composite gels, which being used as a high tough hydrogel for wide application, was provided by the results of this paper.