Nano@Tech seminars continue with Dr. Virendra Singh, postdoctoral fellow in the Georgia Tech School of Mechanical Engineering, on "Template-assisted Synthesis of Polythiophene Nanostructures Towards Their Application as Thermal Interface Materials"

Due to current budget restraints, lunch is provided only to those who have preregistered.

Abstract:
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.

About the Speaker:
Dr. Virendra Singh is Post-doctoral Research Associate in the Nano Engineered System and Transport (NEST) laboratory in the School of Mechanical Engineering. He received his MS and M. Phil degrees, both in Analytical Chemistry, from the Indian Institute of Technology, Roorkee, India; and PhD in Physical Chemistry from Panjab University, Chandigarh, India. In 2007, after completion of his PhD, he moved to Georgia Tech. He was a postdoc in Chemical Engineering with Prof. Behrens from 2007 to 2009, before joining the NEST lab. He has taught several courses as a visiting lecturer and has over 16 publications in refereed journals and proceedings. His current research interests include fabrication and characterization of conjugated polymer and conjugated polymer-CNT hybrid nanostructures, electrochemical polymerization/deposition, and CNT dispersion in non-aqueous solvents.