| Herein we present synthesis schemes and characterization results for polymer matrix nanocomposite reinforced with organically modified layered silicates. These host materials with ultrafine dimensions are promising candidates for polymer and have been previously shown to yield substantial property enhancements at low silicate loadings due to their extreme geometry.; Siloxane nanocomposites with a variety of nanostructures were formed. Thermal stability, solvent uptake and moduli of the nanocomposites were explores. Exfoliated nanocomposites displayed enhanced properties when compared to unreinforced siloxanes, and at lower volume fraction filler than in conventional composites. Large amounts of bound polymer, polymer affected by the silicate, were found in exfoliated nanocomposites as a result of the extreme geometry of the layered silicate. This bound polymer was related to the dramatic property enhancements in the nanocomposites. The behavior of these nanocomposites is compared to behavior expected from traditional models developed for conventional composites and model elastomeric networks.; A lightly brominated polymer has been intercalated into a single crystal of organically exchanged vermiculite. The intercalation was followed using x-ray diffraction by monitoring the gallery height of the vermiculite host. Rutherford Backscattering Spectroscopy, used to confirm polymer intercalation, showed a constant bromine content in the direction normal to the layers. Atomic Force Microscopy images of a cleaved polymer-intercalated crystal showed raised hemispheres on an otherwise flat background. The hemispheres consist of single chains or aggregates of 3-40 polymer chains resulting from relaxations following cleaving.; Three component or Hansen solubility parameters ({dollar}delta){dollar} of organically modified layered silicates, the reinforcing agent in polymer matrix nanocomposites presented herein, have been determined. Two experimental techniques, temporal turbidimetry and sedimentation volume measurements, have been used to determine dispersability behavior of the layered silicates with an array of solvents. The two techniques gave results which were in good agreement with each other. Maps of dispersability or solubility spheres were developed to serve as a guide for solvent behavior for both neat solvents and mixtures. First attempts were made at relating the solubility parameters developed herein to previously reported surface tension values. Also, preliminary attempts have been made at using the solubility parameters as aid in predicting polymer matrix nanocomposite behavior. |
