Novel conductive polymer blends

This thesis presents, for the first time, a comprehensive survey on the subject of self-assembled, multi-encapsulated structures for ternary, quaternary, and quinary polymer blends demonstrating complete wetting. The work targets the development of novel conductive devices possessing low percolation threshold concentrations of conductive polymer. The blends studied are comprised of conductive polyaniline and four commercial polymers: HDPE, PS, PMMA, and PVDF.In the second part of the study, a novel 3D porous polymeric conducting device is derived from multi-percolated polymer blend systems. The work has focused on the preparation of ultra-low surface area porous substrates followed by the deposition of polyanilene conductive polymer (PANI) on the internal porous surface using a layer-by-layer self-assembly technique. The approach reported here allows for the percolation threshold concentration of polyaniline conductive polymer (PANI) to be reduced to values as low as 0.19%. Ternary and quaternary multi-percolated systems comprised of high-density polyethylene(HDPE), polystyrene(PS), poly(methyl methacrylate)(PMMA) and poly(vinylidene fluoride)(PVDF) are prepared by melt mixing and subsequently annealed in order to obtain large interconnected phases. Selective extraction of PS, PMMA and PVDF result in a fully interconnected porous HDPE substrate of ultra low surface area and highly uniform sized channels. This provides an ideal substrate for subsequent polyaniline(PANI) addition. Using a layer-by-layer(LbL) approach, alternating poly(styrene sulfonate)(PSS)/PANI layers are deposited on the internal surface of the 3-dimensional porous polymer substrate. The PANI and sodium poly(styrene sulfonate)(NaPSS) both adopt an inter-diffused network conformation on the surface. The sequential deposition of PSS and PANI has been studied in detail and the mass deposition profile demonstrates oscillatory behavior following a zigzag-type pattern. The presence of salt in the deposition solution results in a more uniform deposition and more thickly deposited PSS/PANI layers.The final part of the work focuses on the complex morphological structures which can be generated from a ternary polymer blend demonstrating complete wetting behavior. This work examines the complete range of possible morphological states for such a system over the entire ternary composition diagram as prepared by melt mixing. A ternary polymer blend comprised of HDPE, PS, and PMMA is selected as a model system demonstrating complete wetting. The positive spreading coefficient of lambdaPS/PMMA=2.6 mN/m indicates that PS separates the HDPE and PMMA phases. Four thermodynamically stable sub-categories of morphologies can be identified: a) matrix/core-shell dispersed phase b) tri-continuous c) bi-continuous/dispersed phase and d) matrix/two separate dispersed phases. Electron microscopy as well as focused ion beam irradiation and atomic force microscopy are used to clearly illustrate and identify the various phases. Solvent extraction/gravimetry is used to examine the extent of continuity of the systems so as to effectively identify regions of high continuity. (Abstract shortened by UMI.)In the first part of this study, a solid, 3D, low percolation threshold conductive device prepared through the control of multiple encapsulation effects in a five-component polymer blend system through melt processing is fabricated. This multi-percolated structure approach is thermodynamically controlled and is described by the Harkins spreading theory, demonstrating spreading of all phases, including the conductive polymer phase, throughout the blend. A quinary blend of PANI and four other components: polyethylene (PE), polystyrene (PS), poly(methyl methacrylate) PMMA, and poly(vinylidene fluoride) (PVDF) are precisely selected to show multi-percolated structure with a percolation threshold less than 5%. In order to locate PANI at the core of this quadruple-percolated structure, all the interfacial tensions between phases must satisfy the Harkins equation and show various complete wetting morphologies with the desirable hierarchical ordering of the phases (HDPE|PS|PMMA|PVDF|PANI). The detailed morphology and continuity diagrams of binary, ternary, quaternary, and finally, quinary systems for PE, PS, PMMA, PVDF, and PANI, are progressively studied in order to systematically demonstrate the concentration regimes resulting in the formation of these novel multiple-encapsulated morphological structures.