Temperature and Molecular Weight Dependent Hierarchical Equilibrium Structures in Semiconducting Poly(3-hexylthiophene)

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Wu, Zhiyong ; Petzold, Albrecht ; Henze, Thomas ; Thurn-Albrecht, Thomas ; Lohwasser, Ruth H. ; Sommer, Michael ; Thelakkat, Mukundan:
Temperature and Molecular Weight Dependent Hierarchical Equilibrium Structures in Semiconducting Poly(3-hexylthiophene).
In: Macromolecules. Bd. 43 (2010) Heft 10 . - S. 4646-4653.
ISSN 1520-5835
DOI: https://doi.org/10.1021/ma902566h

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Abstract

We report on structural investigations of a series of regioregular poly(3-hexylthiophene) with well-defined molecular weight (5−19 kg/mol) using DSC, small angle and wide-angle X-ray scattering, and AFM. With increasing temperature, we identify three ordered phases, namely 3D crystalline, 2D crystalline with disordered side chains, and a layered phase of smectic symmetry, followed by complete melting. Although all samples crystallize in extended chain conformation, the lower molecular weight material exhibits a lower crystallinity, most likely caused by noncrystallizable end groups. The crystallinity increases strongly with increasing molecular weight, which could be a possible explanation for the known dependence of charge transport properties on molecular weight.