DOI: https://doi.org/10.29363/nanoge.inform.2019.008
Publication date: 8th January 2019
The optoelectronic landscape of conjugated polymers is highly dependent on their molecular arrangement and packing, with minute changes in local order, such as chain conformation and torsional backbone order/disorder, frequently having a substantial effect on macroscopic properties.[1-3] Here, we show that blending semiconducting polymers with insulating commodity plastics, an approach previously shown to benefit charge transport[4,5] and improve flexibility,[6] enables controlled manipulation of semiconductor backbone planarity. The key is to create a polarity difference between the semiconductor backbone and its side chains, while matching the polarity of the side chains and the additive. We demonstrate the applicability of this approach by judicious comparison of regioregular poly(3-hexylthiophene) (P3HT) with two of its more polar derivatives, namely the diblock copolymer poly(3-hexylthiophene)-block-poly(ethylene oxide) (P3HT-b-PEO) and the graft polymer poly[3-but(ethylene oxide)thiophene] (P3BEOT), as well as their blends with poly(ethylene oxide) (PEO). Proximity between polar side chains and a similarly polar additive reduces steric hindrance between individual chain segments by essentially ‘expelling’ the side chains away from the semiconducting backbones. This process, shown to be facilitated via exposure to polar environments such as humid air/water vapor, facilitates backbone realignment towards specific chain arrangements, thereby enabling control of backbone planarity graft polymers with aqueous/ionic compatiblity that are usually torsionally disordered.[7]
MD, PS and NS thank the UK’s Engineering and Physical Sciences Research Council (EPSRC) for funding via the Centre for Doctoral Training in Plastic Electronics Materials (EP/G037515/1). MD, NS, PS, SH and EL also thank the Marie Skłodowska-Curie Actions Innovative Training Network “H2020-MSCAITN-2014 INFORM – 675867”. JM furthermore thanks MINECO for the Ramón y Cajal contract and the Ikerbasque Foundation for the Ikerbasque Research Fellow program; and NS gratefully acknowledges additional support from the IdEx Bordeaux Excellence program (ANR-10-IDEX-03-02). PDT and HE thank funding from the European Union Seventh Framework Program (FP7/2010 SYNABCO n° 273316 and FP7/2011 under grant agreement ESTABLIS n° 290022). This work is based upon research conducted at the Cornell High Energy Synchrotron Source (CHESS) which is supported by the National Science Foundation under award DMR-1332208.