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The crystallization behavior of poly(ethylene oxide) (PEO) was studied in the presence of an inorganic filler surface (sodium montmorillonite) with DSC, as well as isothermal cross-polarization optical microscopy. Crystallization of PEO is found to be inhibited, exhibiting a decrease of spherulite growth rate and crystallization temperature. However, the overall crystallization rate increases with silicate loading as a result of extra nucleation sites, which occur in the bulk PEO matrix (i.e., far from the silicate surfaces). PEO differs from other systems, where crystallinity is typically enhanced next to such surfaces, in that the polymer is amorphized near the montmorillonite surfaces. This behavior is attributed to the specific way that PEO interacts with Na+ montmorillonite, where strong coordination of PEO to the surface Na+ cations promotes noncrystalline (ether crown) PEO conformations.

Molecular dynamics simulations are used to explore poly(ethylene oxide)/Li+ complexes, comparing bulk and nanoscopically confined systems. We focus on lithium ion dynamics, so as to elucidate the molecular mechanisms of ionic motion in these two environments. The confined systems mimic 0.8 nm thin intercalates between mica-type layers (montmorillonite). Simulations of the Li+/bulk PEO system show a clear change in the ion transport mechanism from a hopping fashion, at low temperatures, to a random Brownian-like diffusion, at higher temperatures. In sharp contrast, the intercalated, nanoconfined, systems display a single hopping mechanism throughout the same temperature range, dictated by the unique nature of the lithium coordination to the mica-type surfaces and the confined PEO.

The synthetic routes and materials properties of polypropylene/montmorillonite nanocomposites are reviewed. The nanocomposite formation is achieved in two ways: either by using functionalized polypropylenes and common organo-montmorillonites, or by using neat/unmodified polypropylene and a semi-fluorinated organic modification for the silicates. All the hybrids can be formed by solventless melt-intercalation or extrusion, and the resulting polymer/inorganic structures are characterized by a coexistence of intercalated and exfoliated montmorillonite layers. Small additionstypically less than 6 wt %of these nanoscale inorganic fillers promote concurrently several of the polypropylene materials properties, including improved tensile characteristics, higher heat deflection temperature, retained optical clarity, high barrier properties, better scratch resistance, and increased flame retardancy.

Poly(vinyl alcohol)/sodium montmorillonite nanocomposites of various compositions were created by casting from a polymer/silicate water suspension. The composite structure study revealed a coexistence of exfoliated and intercalated MMT layers, especially for low and moderate silicate loadings. The inorganic layers promote a new crystalline phase different than the one of the respective neat PVA, characterized by higher melting temperature and a different crystal structure. This new crystal phase reflects on the composite materials properties. Namely, the hybrid polymer/silicate systems have mechanical, thermal, and water vapor transmission properties, which are superior to that of the neat polymer and its conventionally filled composites. For example, for a 5 wt % MMT exfoliated composite, the softening temperature increases by 25 °C and the Young's modulus triples with a decrease of only 20% in toughness, whereas there is also a 60% reduction in the water permeability. Furthermore, due to the nanoscale d...

Monte Carlo and molecular dynamics computer simulations are used to explore the atomic scale structure and dynamics of intercalated PEO/montmorillonite nanocomposites. Particular attention is paid ...

Our continuing study of the mechanism of flammability reduction of polymer−layered-silicate nanocomposites has yielded results for polypropylene-graft-maleic anhydride and polystyrene−layered-silicate nanocomposites using montmorillonite and fluorohectorite. Cone calorimetry was used to measure the heat release rate and other flammability properties of the nanocomposites, under well-controlled combustion conditions. Both the polymer−layered-silicate nanocomposites and the combustion residues were studied by transmission electron microscopy and X-ray diffraction. We have found evidence for a common mechanism of flammability reduction. We also found that the type of layered silicate, nanodispersion, and processing degradation have an influence on the flammability reduction.

When a combination of microcontact printing and chemical coupling reaction is used, well-defined and robust micropatterns of poly(phenylene vinylene) are fabricated. This approach provides a simple and convenient route to pattern many other types of conducting polymers with a wide range of organic functionalities.