In situ growth of organically-modified magnesium silicate clays within poly(ethylene oxide) matrices to prepare hybrid n
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In situ growth of organically-modified magnesium silicate clays within poly(ethylene oxide) matrices to prepare hybrid nanocomposites Bénédicte Lebeau1, Nicola T. Whilton2* and Stephen Mann2 1 Laboratoire de Matériaux Minéraux, CNRS UMR 7016 – ENSCMu – UHA, 3 rue Alfred Werner, 68093 Mulhouse Cedex, France 2 School of Chemistry, University of Bristol, Bristol BS1 8TS, UK
ABSTRACT A direct synthetic method has been developed to produce hybrid materials composed of polymeric matrices infiltrated with layered inorganic particles. Magnesium chloride hexahydrate and (3-aminopropyl)triethoxysilane (ATES) were employed to produce lamellar organicallymodified magnesium silicate clays with structures analogous to the inorganic 2 :1 phyllosilicates. Amino-functionalised Mg-phyllosilicates were prepared inside a poly(ethylene oxide) (PEO) matrix under quasi non-aqueous conditions. Nanostructured PEO-organoclay composites in bulk and films have been prepared with different layered inorganic particle loadings. X-ray diffraction patterns recorded showed for all samples reflections characteristic of crystalline PEO and layered magnesium organosilicate. Increasing the inorganic content of the composites resulted in the disappearance of the X-ray reflections characteristic of crystalline PEO. INTRODUCTION The current interest in inorganic-organic hybrid materials is mainly concerned with the potential of producing materials with physical and chemical properties that are dramatically different from their bulk counterparts [1]. Polymers reinforced by inorganic particles offer several advantages; for example, moulding and extrusion may be viable with finer reinforcing particles, and structural composites with tunable optical and magnetic properties should be possible. A particular and growing interest has been devoted in the last few years to the elaboration of polymer-layered silicate nanocomposites [2]. Indeed, such hybrid materials exhibit improved properties when compared to pure polymers or conventional composites. These include modulus and strength, decreased gas permeability, increased solvent and heat resistance and decreased flammability. Nanoparticle composites cannot be processed by conventional methods involving suspensions of particles in liquids or low viscosity-resins. As particles become finer, colloidal forces become relatively more important and it becomes more difficult to achieve unagglomerated dispersions at high volume fraction. One solution to this difficulty is to avoid dispersing a preformed reinforcing phase and instead grow the particle phase in the matrix. This is a biomimetic approach in that mineralized biological structures generally are formed by growth in situ rather than transport of preformed particles [3]. This paper describes a new synthetic method that produces hybrid materials composed of polymeric matrices infiltrated with layered inorganic particles. Nanostructured polyethylene oxide (PEO)-organoclay composites have been prepared as bulk and thin films by adding (3aminopropyl)triethoxysilane (A
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