|Raithel, D.; Simine, L.; Pickel, S.; Schötz, K.; Panzer, F.; Baderschneider, S.; Schiefer, D.; Lohwasser, R.H.; Köhler, J.; Thelakkat, M.; Sommer, M.; Köhler, A.; Rossky, P.J.; Hildner, Richard: Direct observation of backbone planarization via side-chain alignment in single bulky-substituted polythiophenes, Proceedings of the National Academy of Sciences of the United States of America 115(11), 2699-2704 (2018) -- DOI: 10.1073/pnas.1719303115|
Conjugated polymers are promising materials for flexible electronics and photovoltaics. Recent progress in polymer design led to a rise in device efficiency. Tailoring intramolecular interactions is a central design element, which allows fine-tuning of optical and electronic properties. However, prediction and measurement of intrinsic properties of newly synthesized polymers is challenging, as they are often hidden by ensemble effects. Single-molecule spectroscopy allows revelation of the intrinsic changes upon chemical modification, here specifically a variation of the side chains. Surprisingly, a more disordered, bulky side chain leads to a higher order and better conjugation within the electronically active backbone of a single chain. This study gives detailed insights into changes in photophysical properties and suggests new ideas for synthesis.