Showing papers on "Polymer nanocomposite published in 1996"

Polymer Layered Silicate Nanocomposites

Abstract: Polymer nanocomposites with layered silicates as the inorganic phase (reinforcement) are discussed. The materials design and synthesis rely on the ability of layered silicates to intercalate in the galleries between their layers a wide range of monomers and polymers. Special emphasis is placed on a new, versatile and environmentally benign synthesis approach by polymer melt intercalation. In contrast to in-situ polymerization and solution intercalation, melt intercalation involves mixing the layered silicate with the polymer and heating the mixture above the softening point of the polymer. Compatibility with various polymers is accomplished by derivatizing the silicates with alkyl ammonium cations via an ion exchange reaction. By fine-tuning the surface characteristics nanodispersion (i. e. intercalation or delamination) can be accomplished. The resulting polymer layered silicate (PLS) nanocomposites exhibit properties dramatically different from their more conventional counterparts. For example, PLS nanocomposites can attain a particular degree of stiffness, strength and barrier properties with far less inorganic content than comparable glass- or mineral reinforced polymers and, therefore, they are far lighter in weight. In addition, PLS nanocomposites exhibit significant increase in thermal stability as well as self-extinguishing characteristics. The combination of improved properties, convenient processing and low cost has already led to a few commercial applications with more currently under development.

Concurrent Polymerization and Insertion of Aniline in Molybdenum Trioxide: Formation and Properties of a [Poly(aniline)]0.24MoO3 Nanocomposite

Abstract: We have developed a novel nanocomposite material, [PANI]0.24MoO3, comprised of poly(aniline) chains interleaved with the layers of MoO3, using concomitant ion exchange−polymerization in the presence of an external oxidizing agent. The characterization of this material using SEM, FTIR spectroscopy, powder XRD, and thermal analysis shows that the poly(aniline) is present primarily in the emeraldine salt form. The high degree of ordering evident from the oriented film XRD patterns suggests that the PANI chains are at least partially aligned in the ac (basal) plane. The properties of the polymer nanocomposite for electrochemical lithium insertion were compared to those of the alkali molybdenum oxide using the materials as cathodes in conventional lithium cells. The polymer/oxide battery demonstrated substantially reduced cell polarization on galvanostatic cycling, compared to the alkali molybdenum oxide in the absence of PANI. The resultant enhanced ion and/or electron transport induced by incorporation of th...

Subnanometer-Diameter Wires Isolated in a Polymer Matrix by Fast Polymerization

Abstract: The preparation and analysis of inorganic-organic polymer nanocomposites consisting of inorganic nanowires and multiwire "cables" in a random-coil organic polymer host is reported. Dissolution of inorganic (LiMo3Se3)n wires in a strongly coordinating monomer, vinylene carbonate, and the use of a rapid polymerization in the presence of a cross-linking agent produce nanocomposites without phase separation. Polymerization of dilute solutions yields a material containing mostly (Mo3Se3(-))n mono- and biwires, 6 to 20 angstroms in diameter and 50 to 100 nanometers long. Polymerization of more concentrated liquid crystalline solutions yields a nanocomposite containing oriented multiwire cables, 20 to 40 angstroms in diameter and up to 1500 nanometers long, that display optical anisotropy and electrical conductivity.

Polymer nanocomposite formation by emulsion synthesis

Abstract: The formation of a nanocomposite by emulsion polymerization is described. The invention includes the nanocomposite latex, a solid nanocomposite of a layered silicate mineral intercalated with an emulsion polymer and blends of the solid nanocomposite with other polymers.

Modification of Polyolefins: An Overview

Abstract: Polymer-polymer blends are the most exciting and promising area for generating novel materials with improved properties in relatively short development times [11. Among different types of blends one can distinguish two important categories. The first category involves homogeneous polymer alloys, which exhibit properties intermediate between those of the individual components following a simple monotonic function that depends on the ratio of the two polymers in the blend. The other category involves heterogeneous polymer blends, wherein one polymer (Polymer A) is dispersed within the other polymer, a continuous phase (Polymer B, Fig. 1) and they are immiscible. This type of blend has an important potential advantage in that it provides the additivity of the phase properties along with new features derived from a unique and particular morphology. For such engineered properties, the dispersed phase should be evenly dispersed in finely divided domains throughout the continuous phase. Such properties ...

Low driving voltage polymer dispersed liquid crystal display device with conductive nanoparticles

Abstract: A reduced driving voltage polymer dispersed liquid crystal display (10) has a transparent polymer matrix (20) disposed between two substrates (12, 14). Droplets of a nematic liquid crystal fluid (22) are uniformly dispersed throughout the polymer matrix. Particles of an optically transparent material (24) that is a weak conductor are uniformly dispersed throughout the polymer matrix to reduce the electrical potential across the polymer. The enhanced conductivity of the polymer matrix allows the display to be operated at a reduced voltage.

Fabrication and Characterization of Light Emitting Porous Silicon and Polymer Nanocomposites

Abstract: We report the fabrication of nanocomposites by the infiltration of polymers into porous silicon. Polymers such as polyamide, polystyrene, PMMA, and PVC were chosen because they are commonly available and have been extensively studied. The pore-filling was accomplished by either diffusion of the polymer molecules into porous silicon or in-situ polymerization of the monomer. The Vickers hardness arid the thermal conductivity of the samples were measured. There was a difference in the nanocomposite characteristics depending on whether the samples were as-anodized or had been annealed in oxygen. By infiltrating polyamide into an as-anodized sample, a 42% increase in hardness and a 24% increase in thermal conductivity were observed at room temperature, without any degradation of luminescence.

Direct Observation of Fracture Mechanisms in Polymer-Layered Silicate Nanocomposites

Abstract: Conventional three point bending and TEM techniques are employed to determine the fracture toughness and identify the failure mechanisms in model layered-silicate polymer nanocomposites.

4-Methyl-1-pentene polymer compositions

Abstract: A 4-methyl-1-pentene polymer composition is prepared by melt mixing (A) a 4-methyl-1-pentene polymer, (B) a 1-butene polymer, (C) a propylene polymer, and (D) a triblock copolymer of polystyrene/ethylene-butylene copolymer/polystyrene and/or a triblock copolymer of polystyrene/ethylene-propylene copolymer/polystyrene. The composition has improved gas permeability, flexibility, and mechanical properties and is formed into a film which is heat sealable.

Process for preparing polymer powders which are redispersible in aqueous media

Abstract: The production of polymer powder comprises drying an aqueous dispersion of a polymer (A) in which the dispersed particles have a positive or negative electric charge on the surface. The process comprises adding, as auxiliary drying agent, a polyelectrolyte (B) which, in its dissociated form as poly-ion and counter-ion is soluble in the aqueous dispersion medium and in which the charge on the poly-ion is opposite to the surface charge on the dispersed polymer. Also claimed are: (i) the polymer powder obtained by this process; and (ii) the polymer powder containing charged spherical particles of (A) and a polyelectrolyte (B).

Composite polymer electrolytic film

Abstract: PROBLEM TO BE SOLVED: To provide a polymer solid electrolyte which has its high ion conductivity and mechanical strength SOLUTION: This film is so form as to carry a polymer gel made of organic electrolyte and polymer in the internal fine pore of an expanded porous polytetra fluoro-ethylene In this case, the polymer component of the polymer gel has a bridge structure, the structural formula is preferably include a copolymer of compounds expressed by: R1 R2 C=CR3 COOR4 or R1 R2 C=CR3 OCOR4 (each R is the same or different and hydrogen or organic group of valency 1

Efficient Electronic Energy Transfer in Polymer Nanocomposite Assemblies.

Abstract: : Electronic energy transfer plays a critical role in biological photosynthesis, artificial photosynthesis, photovoltaic devices, photocatalysis, and other multichromophore systems and photoinduced processes. Our studies of electronic energy transfer in novel thin film light-harvesting nanocomposite polymer assemblies consisting of a rod-coil copolymer antenna and a conjugated polymer energy trap are presented. Total singlet electronic energy transfer efficiencies as high as 93% were observed at energy trap concentrations as low as 9 mol %. It will be shown that the efficiency of energy transfer can be regulated by the supramolecular structure of the rod-coil copolymer (antenna component). The nanoscale morphology of the nanocomposite polymer systems was characterized by the technique of nonradiative energy transfer, revealing interchromophore distances of 1.0-2.5 nm in the series of materials investigated.

Studies of polymer ball type polymer dispersed liquid crystal films

Abstract: Polymer dispersed liquid crystals ( PDLC ) are potentially useful as new types of display devices. By applying an electric field, one can switch the PDLC cell from a highly scattering opaque state to a transparent state. Normal PDLC cells consist of liquid crystal droplets, having sizes on the order of micrometers, embedded in a transparent polymer matrix. In this paper, we report the development of a new kind of PDLC cell with a distinct type of polymer morphology, referred to as “reverse ” or “polymer ball” type. The electro-optical behavior and the micro structure of the PDLC films were investigated by a He-Ne laser and the scanning electron microscopy ( SEM ), respectively.