Preparation of poly(vinyl acetate-co-dibutyl maleate)/ sodium-montmorillonite nanocomposite via in situ reverse iodine transfer radical polymerization

Abstract

Among other controlled radical polymerization techniques, reverse iodine transfer radical polymerization (RITP) has recently been developed for synthesis of polymers with controlled characteristics. In the present work, poly(vinyl acetate-co-dibutyl maleate)/ sodium montmorillonite (Na-MMT) nanocomposites were synthesized via bulk RITP of the vinyl acetate and dibutyl maleate in the presence of Na-MMT, molecular iodine and 2,2′-azobis(isobutyronitryle) (AIBN) at 70 °C. Effect of the Na-MMT loading on the conversion, molecular weight and its distribution were studied by 1H-NMR and GPC analyses respectively. Structure of the nanocomposites was investigated by XRD and TEM analyses. It was found that under similar conditions, conversion, copolymerization rate and molecular weight of the produced copolymers decrease in the presence of Na-MMT especially when the higher loading of nanoclay (5 wt%) is used. Also, molecular weight distribution increased in the presence of clay. It can be attributed to the existence of an interaction between the functional groups in the clay’s surface and the reactants as well as probably to the undesirable chain transfer reactions in the presence of nanoclay. Moreover, results showed that conversion and molecular weight of the copolymer increase by increasing iodine amount in a reaction mixture containing nanoclay, verifying again existence of the interaction between the functional groups in the clay’s surface and the reactants (I2 and monomers). The XRD and TEM results indicated that intercalated structure is formed at a low conversion while exfoliated structure can also be formed at a higher conversion.