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High thermal conductivity of chain-oriented amorphous polythiophene

A Corrigendum to this article was published on 03 July 2014

This article has been updated

Abstract

Polymers are usually considered thermal insulators, because the amorphous arrangement of the molecular chains reduces the mean free path of heat-conducting phonons. The most common method to increase thermal conductivity is to draw polymeric fibres, which increases chain alignment and crystallinity, but creates a material that currently has limited thermal applications. Here we show that pure polythiophene nanofibres can have a thermal conductivity up to 4.4 W m–1 K–1 (more than 20 times higher than the bulk polymer value) while remaining amorphous. This enhancement results from significant molecular chain orientation along the fibre axis that is obtained during electropolymerization using nanoscale templates. Thermal conductivity data suggest that, unlike in drawn crystalline fibres, in our fibres the dominant phonon-scattering process at room temperature is still related to structural disorder. Using vertically aligned arrays of nanofibres, we demonstrate effective heat transfer at critical contacts in electronic devices operating under high-power conditions at 200 °C over numerous cycles.

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Figure 1: Microstructure of polythiophene nanofibres.
Figure 2: Thermal conductivity measurements of single fibres and vertically aligned arrays.
Figure 3: Application of vertically aligned polythiophene nanofibres as a TIM.
Figure 4: Device demonstration of polythiophene-nanofibre TIM at high temperature.

Change history

  • 17 June 2014

    In the version of this Article originally published, in the section 'Thermal conductivity of individual fibres', the second sentence should have read "The measured thermal conductivity of the several nanofibre samples increases with decreasing diameter..." This error has now been corrected in the online versions of the Article.

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Acknowledgements

This work was supported by the National Science Foundation (NSF; grant no. CBET-1133071), a seed grant from the Georgia Tech Center for Organic Photonics and Electronics and an NSF-IGERT graduate fellowship for T.L.B. The work of Y.C. was supported by the Air Force Office of Scientific Research (award no. FA9550-09-1-0162). The work of K.H.S. was supported by the US Department of Energy, Office of Basic Energy Sciences (award no. DE-SC0002245). The work at UT Austin was supported by the NSF (award no. CBET-0933454). A.W. acknowledges support from the NSF Graduate Research Fellowship Program. K.D.B. was supported by the Natural Science Foundation of China (award no. 51205061), the Natural Science Foundation of Jiangsu Province (award no. BK2012340) and the National Basic Research Program of China (award no. 2011CB707605).

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Contributions

V.S., T.L.B. and B.A.C. conceived and designed the experiments. V.S. prepared the samples and performed the material spectroscopy and adhesion tests. T.L.B. performed the photoacoustic measurements. A.W., K.B., M.T.P., S.A.M. and L.S. performed the microbridge measurements. D.P.R., T.R.G. and D.H.A. performed the SiC chip tests. Y.C. and K.H.S. provided the TEM images and crystallinity characterization. W.L. and A.H. provided the single chain simulations. V.S., T.L.B. and B.A.C. analysed and discussed the data. V.S., T.L.B. and B.A.C. co-wrote the manuscript. All authors commented on the manuscript.

Corresponding author

Correspondence to Baratunde A. Cola.

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Competing interests

Georgia Tech has applied for a patent, application no. PCT/US 61/484,937, related to the design methods and materials produced in this work. Nanostructured composite polymer thermal/electrical interface material and method for making the same, B.A. Cola, K. Kalaitzidou, H.T. Santoso, V. Singh, US 2012/0285673 A1, November 15, 2012.

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Singh, V., Bougher, T., Weathers, A. et al. High thermal conductivity of chain-oriented amorphous polythiophene. Nature Nanotech 9, 384–390 (2014). https://doi.org/10.1038/nnano.2014.44

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