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The molecular basis of mesophase ordering in a thiophene-based copolymer



Dean M. DeLongchamp, Regis J. Kline, Youngsuk Jung, Eric K. Lin, Daniel A. Fischer, David J. Gundlach, Andrew Moad, Lee J. Richter, Michael F. Toney, Martin Heeney, Iain McCulloch


The carrier mobility of poly(2,5-bis(3-alkylthiophen-2-yl) thieno[3,2-b]thiophene) semiconductors can be substantially enhanced after heating through a thermotropic mesophase transition, which causes a significant improvement in thin film structural order. By directly measuring film structure throughout a heating and cooling cycle, we identify the molecular origin of this mesophase transition as the melting of interdigitated linear alkane side chains, in this case quaterdecyl. The morphology and phase behavior throughout the thermal cycle is controlled by the changing conformation of the side chains. Surprisingly, the melting of the side chains allows increases in the backbone order, - stacking, and carrier mobility. Upon cooling, the side chains recrystallize to preserve the excellent mesophase order and enhanced electrical performance.


liquid crystal, mesophase, OFET, OTFT, P3HT, polymer semiconductor, polythiophene


DeLongchamp, D. , Kline, R. , Jung, Y. , Lin, E. , Fischer, D. , Gundlach, D. , Moad, A. , Richter, L. , Toney, M. , Heeney, M. and McCulloch, I. (2009), The molecular basis of mesophase ordering in a thiophene-based copolymer, Macromolecules, [online], (Accessed June 15, 2024)


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Created February 18, 2009, Updated February 19, 2017