V.I. Uricanu

Synthesis of Polyvinylacetate‐Sodium Montmorillonite Hybrids by Emulsion Polymerization in the Presence of Anionic Surfactants

The emulsion polymerisation of vinyl acetate (VAc) in presence of sodium dodecylsulphate (SDS) and sodium montmorillonite (NaMMT) is used in order to achieve polymer‐clay hybrids. The influence of the polyvinylacetate (PVAc), SDS, and PVAc‐SDS complex on the NaMMT structure also was investigated. The VAc emulsion polymerization rate exhibits a maximum as the NaMMT concentration increases. The XRD patterns correspond to hybrids with intercalated structure. If a water soluble comonomer, ammonium sulphato ethylmethacrylate (ASEMA) is used for copolymerization with VAc, a exfoliated hybrid structure (from XRD spectra) is obtained. The solid materials were analysed by TGA, FTIR, XRD, SEM, and TEM.

Variable morphologies of poly(vinyl acetate)–montmorillonite nanocomposites obtained by emulsion polymerization in the presence of poly(vinyl pyrrolidone)

Abstract Nanocomposites containing poly(vinyl acetate) and montmorillonite (MMT) were prepared using a one-batch emulsion polymerization recipe, assisted by poly (vinylpyrrolidone). The relative clay concentration with respect to the other reaction partners influences drastically the morphological units in the end-products. For low [MMT], well-defined, spherical PVAc particles are formed. At the other extreme, for high [MMT], production of polymeric, water-swollen aggregates is favored. Depending on the MMT/PVP ratio, the clay will be dispersed in the final polymer matrix in variable forms, from individual platelets to agglomerates of reformed tactoids.

Emulsion homo- and copolymerization of vinyl acetate in the presence of maleic-modified and unmodified silica

The emulsion homo- and copolymerization of vinyl acetate in the presence of maleic-modified and unmodified silica were investigated. The formation of surfactant admicelles onto the silica surface induces a decrease of the surfactant concentration in water. It was shown that an increase of the functionalization degree of the inorganic support led to a decrease of the initiator conversion during homopolymerization. The same effect, along with the increase of the initiator productivity, was caused by the enhancement of the amount of unmodified silica during the copolymerization of vinyl acetate with bis(2-ethylhexyl)maleate. Vinyl acetate copolymerization with the maleic-modified support was suggested by the oxidation phenomenon taking place during the heating of the formed polymers in air and by Tg measurements.