Preparation of polystyrene colloid particles armored by clay platelets via dispersion polymerization

Polystyrene colloid particles armored by Montmorillonite clay (MMT) were prepared by free-radical polymerization in dispersion. MMT was pre-modified with cationic amphiphilic block copolymer of poly(styrene-b-2-hydroxyethyl acrylate) (PS-b-PHEA), and the obtained (PS-b-PHEA)-MMT modified clay was used as stabilizer in dispersion polymerization. The impact of (PS-b-PHEA)-MMT loading on the particle size, the monomer conversion, and on the molecular weight were investigated. The main objective of this paper was to use the clay platelets as stabilizers in dispersion polymerization, and as nanofiller to improve some polymer properties such as thermal stability, thermo-mechanical and melt flow properties. Transmission electron microscopy (TEM) showed that colloid PS particles with MMT layers at the surface (i.e. armored particles) were obtained, and the particles sizes were found to be in the micrometer size range and stable dispersion were obtained for clay loadings up to 5wt%. Small angle X-ray diffractions (XRD) and TEM revealed that polymer-clay nanocomposites (PCNs) with partially exfoliated structures were obtained for low clay loading, while intercalated structures were obtained at higher clay loading. All PCNs were found to be more thermally stable than neat polymer as were determined by TGA. Furthermore, an increase in the storage modulus and the T g of the PCNs was found and greatly correlated to the clay loading. © 2011 Elsevier Ltd. All rights reserved

Preparation of polystyrene-clay nanocomposites via dispersion polymerization using oligomeric styrene-montmorillonite as stabilizer

This study describes the preparation of polystyrene-clay nanocomposite (PS-nanocomposite) colloidal particles via free-radical polymerization in dispersion. Montmorillonite clay (MMT) was pre-modified using different concentrations of cationic styrene oligomeric ('PS-cationic'), and the subsequent modified PS-MMT was used as stabilizer in the dispersion polymerization of styrene. The main objective of this study was to use the clay platelets as fillers to improve the thermal and mechanical properties of the final PS-nanocomposites and as steric stabilizers in dispersion polymerization after modification with PS-cationic. The correlation between the degree of clay modification and the morphology of the colloidal PS particles was investigated. The clay platelets were found to be encapsulated inside PS latex only when the clay surface was rendered highly hydrophobic, and stable polymer latex was obtained. The morphology of PS-nanocomposite material (after film formation) was found to range from partially exfoliated to intercalated structure depending on the percentage of PS-MMT loading. The impact of the modified clay loading on the monomer conversion, the polymer molecular weight, the thermal stability and the thermomechanical properties of the final PS-nanocomposites was determined. © 2012 Society of Chemical Industry

Preparation of polystyrene colloid particles armored by clay platelets via dispersion polymerization

Polystyrene colloid particles armored by Montmorillonite clay (MMT) were prepared by free-radical polymerization in dispersion. MMT was pre-modified with cationic amphiphilic block copolymer of poly(styrene-b-2-hydroxyethyl acrylate) (PS-b-PHEA), and the obtained (PS-b-PHEA)-MMT modified clay was used as stabilizer in dispersion polymerization. The impact of (PS-b-PHEA)-MMT loading on the particle size, the monomer conversion, and on the molecular weight were investigated. The main objective of this paper was to use the clay platelets as stabilizers in dispersion polymerization, and as nanofiller to improve some polymer properties such as thermal stability, thermo-mechanical and melt flow properties. Transmission electron microscopy (TEM) showed that colloid PS particles with MMT layers at the surface (i.e. armored particles) were obtained, and the particles sizes were found to be in the micrometer size range and stable dispersion were obtained for clay loadings up to 5wt%. Small angle X-ray diffractions (XRD) and TEM revealed that polymer-clay nanocomposites (PCNs) with partially exfoliated structures were obtained for low clay loading, while intercalated structures were obtained at higher clay loading. All PCNs were found to be more thermally stable than neat polymer as were determined by TGA. Furthermore, an increase in the storage modulus and the T g of the PCNs was found and greatly correlated to the clay loading. © 2011 Elsevier Ltd. All rights reserved

Impact of the clay organic modifier on the morphology of polymer-clay nanocomposites prepared by in Situ free-radical polymerization in emulsion

Poly(styrene-co-butyl acrylate) copolymers were prepared by free-radical random copolymerization of styrene and butyl acrylate in emulsion in the presence of 10% of surface-modified sodium montmorillonite (Na-MMT). The objective of this work was to evaluate the impact of the clay organic modifier in terms of its chemical structure, its degree of interaction within the clay galleries surface, and its ability to copolymerize with monomers, on the morphology and properties of the final nanocomposite prepared. Na-MMT was modified using different organic modifiers, namely: sodium 1-allyloxy-2- hydroxypropyl (Cops), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), N-isopropylacrylamide (NIPA), and sodium 11-methacryloyloxy-unde-can-1-yl sulfate (MET), respectively. The morphology and properties of the nanocomposites obtained were found to be dependant on the clay organic modifier. X-ray diffraction (XRD) and transmission electron microscopy indicated that, nanocomposites at 10% clay loading with Cops-, NIPA-, and MET-modified clays, yielded intercalated to partially exfoliated structures, whereas AMPS-modified clay gave a nanocomposite with a fully exfoliated structure. All polymer-clay nanocomposites were found to be more thermally stable than neat poly(S-co-BA) as were determined by TGA. However, nanocomposites with intercalated structures exhibited greater thermal stability relative to fully exfoliated ones. Furthermore, nanocomposites with exfoliated structures exhibited higher storage moduli (GI) than partially exfoliated once, whereas intercalated structure showed the lowest GI values. © 2008 Wiley Periodicals, Inc.Articl