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

NIST Authors in Bold

Author(s): 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;
Title: The molecular basis of mesophase ordering in a thiophene-based copolymer
Published: February 18, 2009
Abstract: 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.
Citation: Macromolecules
Volume: 41
Pages: pp. 5709 - 5715
Keywords: liquid crystal,mesophase,OFET,OTFT,P3HT,polymer semiconductor,polythiophene
Research Areas: Polymers, Characterization, Electronics, Semiconductor Materials, Materials Science
PDF version: PDF Document Click here to retrieve PDF version of paper (498KB)