Showing papers by "Emmanuel P. Giannelis published in 1999"

Polymer-silicate nanocomposites : Model systems for confined polymers and polymer brushes

Abstract: The static and dynamic properties of polymer-layered silicate nanocomposites are discussed, in the context of polymers in confined spaces and polymer brushes. A wide range of experimental techniques as applied to these systems are reviewed, and the salient results from these are compared with a mean field thermodynamic model and non-equilibrium molecular dynamics simulations.

Polymers in Confined Environments

Abstract: Phase Transitions of Polymer Blends and Block Copolymer Melts in Thin Films.- Flexible Polymers in Nanopores.- Polymer-Silicate Nanocomposites: Model Systems for Confined Polymers and Polymer Brushes.- Normal and Shear Forces Between Polymer Brushes.- Surface-Anchored Polymer Chains: Their Role in Adhesion and Friction.- Molecular Transitions and Dynamics at Polymer / Wall Interfaces: Origins of Flow Instabilities and Wall Slip.

Direct Polymer Intercalation in Single Crystal Vermiculite

Abstract: A lightly brominated isobutylene bromomethylstyrene copolymer was directly intercalated into a single crystal of organically modified vermiculite. Polymer intercalation was monitored by X-ray diffraction, (XRD) and was confirmed by Rutherford backscattering spectroscopy (RBS). Atomic force microscopy (AFM) images of a cleaved polymer-intercalated crystal showed raised hemispheres on an otherwise flat background. Calculations show these hemispheres to consist of possible chain fractions or single and multiple chains, depending on the reaction time.

Polymer-Layered Silicate Nanocomposites Synthesis, Properties and Applications

Abstract: Polymer nanocomposites, especially polymer-layered silicate (PLS) nanocomposites, represent a radical alternative to conventionally (macroscopically) filled polymers. Because of their nanometer-size dispersion, the nanocomposites exhibit markedly improved properties when compared with the pure polymers or conventional composites. These include increased modulus and strength, decreased gas permeability, increased solvent and heat resistance and decreased flammability. In addition to their potential applications, PLS nanocomposites are also unique model systems to study the structure and dynamics of polymers in confined environments. Using both delaminated and intercalated hybrids, the statics and dynamics of polymers confined over distances ranging from the radius of gyration of the polymer to the statistical segment length of the chains can be studied. © 1998 John Wiley & Sons, Ltd.

Mobility of Polymers in Nanometer Slits: Kinetics of Polymer Melt Intercalation in Layered Silicates

Abstract: Introduction Recently, polymer nanocomposites have attracted a lot of research interest, not only because they exhibit new and improved properties comparing to their bulk counterparts(1), but also because they represent unique model systems to study the statics and dynamics of polymers confined over distances ranging from the statistical segment length to the radius of gyration of the chains. In particular, increased interest has been concentrated on polymer intercalated systems employing 2:1 mica-type phyllo-silicates, such as smectites and hectorites (2) . By following the temporal evolution of X-ray diffraction patterns during polymer melt intercalation into the galleries of layered silicates the nonequilibrium dynamics of polymer chains in a 2 nm slit has been studied. In this paper we will present and discuss the intercalation kinetics of polystyrene as a function of molecular weight, polymer/surface interaction, chain ends and polymer architecture (i.e. random, block and star). Furthermore, structural details obtained from neutron and x-ray scattering will be presented and discussed.