Impact of the clay organic modifier on the morphology of polymer-clay nanocomposites prepared by in Situ free-radical polymerization in emulsion
Journal of Polymer Science, Part A: Polymer Chemistry
Department of Chemistry and Polymer Science, UNESCO Associated Centre for Macromolecules, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa
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.
Acrylic monomers; Alkali metals; Amides; Barium; Catalyst activity; Chemical properties; Chemical reactions; Chemicals; Cobalt; Cobalt alloys; Cobalt compounds; Copolymerization; Electron microscopes; Electron microscopy; Electron optics; Free radical polymerization; Imaging techniques; Ketones; Microfluidics; Microscopic examination; Monomers; Morphology; Nanocomposites; Nanostructured materials; Polymers; Silicate minerals; Sodium; Sodium sulfate; Styrene; Sulfate minerals; Surface properties; Surfaces; Thermodynamic stability; Transmission electron microscopy; X ray analysis; X ray diffraction analysis; (1 1 0) surface; (ethylene vinyl alcohol) copolymers; (PL) properties; Allyloxy; Butyl acrylate (BuA); chemical structures; Clay loadings; Degree of interaction; Exfoliated structures; Free radical polymerization (FRP); Free-radical; In-situ; Intercalated structures; Modified clays; N-isopropylacrylamide (PNIPAAm); nano composites; Organic modifiers; Polymer-clay nanocomposites (PCN); Sodium montmorillonite (NaMMT); Storage modulus; thermal stability; X ray diffraction (XRD); Clay minerals