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arXiv · 1811.08924

Crystallization-Arrested Viscoelastic Phase Separation in Semiconducting Polymer Gels

Jing He·Xiaoqing Kong·Yuhao Wang·Michael Delaney·Dilhan M. Kalyon·Stephanie S. Lee
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Abstract

Through a combination of rheological characterization and temperature-variable imaging methods, a novel gelation pathway in dilute solutions of a semiconducting polymer to achieve interconnected, crystalline networks with hierarchical porosity is reported. Upon rapid cooling, solutions of regioregular poly(3-hexylthiophene) (RR-P3HT) in ortho-dichlorobenzene formed thermoreversible gels. Temperature-variable confocal microscopy revealed cooling-induced structural rearrangement to progress through viscoelastic phase separation. The phase separation process arrested prematurely during the formation of micron-sized solvent-rich "holes" within the RR-P3HT matrix due to intrachain crystallization. Cryogen-based scanning electron microscopy of RR P3HT gels revealed the existence of an interfibrillar network exhibiting nano-sized pores. Remarkably, these networks formed to equal gel strengths when a third component, either small molecule phenyl C61 butyric acid methyl ester (PCBM) or non-crystallizing regiorandom (Rra)-P3HT, was added to the solution. Organic solar cells in which the active layers were deposited from phase-separated solutions displayed 45% higher efficiency compared to reference cells.

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Jing He, Xiaoqing Kong, Yuhao Wang, Michael Delaney, Dilhan M. Kalyon, Stephanie S. Lee. 2018-11-21. Crystallization-Arrested Viscoelastic Phase Separation in Semiconducting Polymer Gels. https://arxiv.org/abs/1811.08924

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