Template Assisted Synthesis of Polythiophene Nanostructures Towards Their Application as Thermal Interface Materials
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Since the realization of the electrical conductivity in conjugated polymers during the late seventies, this class of organic materials has received growing attention due to their technological applications. In addition to their attractive processing properties associated with conventional polymers, conjugated polymers have both electrical and optical properties similar to those of metals and inorganic semiconductors. Similar to traditional non-conjugated polymers, conjugated polymers possess a very low intrinsic thermal conductivity (~ 0.2 W m-1 K-1). Defects in bulk polymers such as chain entanglements, voids, and impurities lead to a significant number of phonon scattering sites that impede heat transfer. The utility of these polymers as thermal interface materials depends largely on (i) the directional carrier mobility through the polymer chain (ii) the contact area and resistance between polymer and surfaces. Further, the alignment of polymer chains with enhanced molecular and superamolecular order at the nanoscale can reduce defects and improve the mechanical strength and thermal/electrical conductivity in the direction of alignment significantly. This presentation will cover the template assisted fabrication of conjugated polymer (polythiophene) nanostructures towards enhanced molecular ordering within nanostructures. The polythiophene (Pth) nanostructures of diameters ~ 200 nm and length up to tens of micron were grown potentiostatically using a three electrode electrochemical cell and a hard nanoporous template. The important fabrication parameters to control the morphology of nanostructures will also be discussed. A photoacoustic (PA) technique was used to measure the thermal resistances of Pth nanotube arrays dry-adhered to a substrate to form the interface. The total thermal resistance of a Pth nanotube interface was measured to be as low as ~ 1 mm2K/W, which is significantly less than the measured resistances for state of art thermal adhesives.
- Nano@Tech Lecture Series