Rational Design of Molecular Thermal Interfaces

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

Technical Abstract: This work is a close collaboration between theory and experiment to design molecular interfaces to tune thermal transport. Using current theoretical tools (e.g. R-matrix theory, Langevin formalism and simulations) and new ones developed under this proposal (e.g. Fokker-Planck analysis of interfaces), we will be able to rapidly analyze and optimize the thermal properties of molecular structures without having to resort to repeated simulations. We will then synthesize these designs and test their thermal conductivity, using these results to improve our theoretical models, which will in turn suggest improved designs. This iterative loop will lead to fundamental progress in the modeling of thermal transport as well as new composites with high thermal conductivity. Our goal is to functionalize the ends of carbon nanotubes so as to minimize their Kapitsa resistance and measure their thermal conductivity. Initially, we will react alcohol [end-group] functionalized nanotubes with acid chlorides to form ester groups. Alternatively, amine [end-group] modified nanotubes will be modified by reaction with the acid chlorides (of the desired end-groups) to form amide linkages[, progressively increasing stiffness of the coupling group]. Finally, interfacial synthetic methods can be used to directly couple end group moieties, such as long chain perfluoroalkyl groups, selectively to the nanotube ends. These methods will also be modified to couple other end groups of interest directly to the nanotubes. These materials will be incorporated into carefully chosen polymer matrices and their thermal conductivities measured. Vibrational coupling of the nanotubes, via the endgroups, to the polymer matrix will be signaled by increases in thermal conductivities of the composites relative to those made using non-modified nanotubes. We will iterate between theory and experiment to study how size, orientation, alignment, connectivity, and interactions with the host material affect thermal conductivity. Non-Technical Abstract: This work is a close collaboration between theory and experiment to design chains of atoms that will be attached to the ends of molecules in order to improve how they conduct heat. Using current theoretical tools and new ones developed under this proposal, we will be able to rapidly optimize how different molecular structures conduct heat without having to resort to repeated simulations. We will then synthesize these designs and test their thermal conductivity, using these results to improve our theoretical models, which will in turn suggest improved designs. Our goal is to design chains of atoms that would be chemically attached to the ends of carbon nanotubes. Carbon nanotubes, themselves, conduct heat as well as many metals, but because they are very stiff, it is difficult to get heat to flow into them from their surrounding medium. We will iterate between theory and experiment to study how size, orientation, alignment, connectivity, and interactions with the host material affect thermal conductivity. Minimizing the resistance to getting heat into and out of carbon nanotubes would be very important. For example, polymer composites could be used in car and truck radiators to replace heavier, costlier metallic components, saving money and fuel; adhesives that conduct heat well could be used in aviation and in electronics to improve high temperature performance and lower the rate of failure. There are hundreds of potential industrial applications.