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Direct observation of backbone planarization via side-chain alignment in single bulky-substituted polythiophenes

Title data

Raithel, Dominic ; Simine, Lena ; Pickel, Sebastian ; Schötz, Konstantin ; Panzer, Fabian ; Baderschneider, Sebastian ; Schiefer, Daniel ; Lohwasser, Ruth H. ; Köhler, Jürgen ; Thelakkat, Mukundan ; Sommer, Michael ; Köhler, Anna ; Rossky, Peter J. ; Hildner, Richard:
Direct observation of backbone planarization via side-chain alignment in single bulky-substituted polythiophenes.
In: Proceedings of the National Academy of Sciences of the United States of America. (2018) . - 6 S..
ISSN 1091-6490
DOI: https://doi.org/10.1073/pnas.1719303115

Official URL: Volltext

Abstract in another language

The backbone conformation of conjugated polymers affects, to a large extent, their optical and electronic properties. The usually flexible substituents provide solubility and influence the packing behavior of conjugated polymers in films or in bad solvents. However, the role of the side chains in determining and potentially controlling the backbone conformation, and thus the optical and electronic properties on the single polymer level, is currently under debate. Here, we investigate directly the impact of the side chains by studying the bulky-substituted poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) and the common poly(3-hexylthiophene) (P3HT), both with a defined molecular weight and high regioregularity, using low-temperature single-chain photoluminescence (PL) spectroscopy and quantum-classical simulations. Surprisingly, the optical transition energy of PDOPT is significantly (∼2,000 cm−1 or 0.25 eV) red-shifted relative to P3HT despite a higher static and dynamic disorder in the former. We ascribe this red shift to a side-chain induced backbone planarization in PDOPT, supported by temperature-dependent ensemble PL spectroscopy. Our atomistic simulations reveal that the bulkier 2,5-dioctylphenyl side chains of PDOPT adopt a clear secondary helical structural motif and thus protect conjugation, i.e., enforce backbone planarity, whereas, for P3HT, this is not the case. These different degrees of planarity in both thiophenes do not result in different conjugation lengths, which we found to be similar. It is rather the stronger electronic coupling between the repeating units in the more planar PDOPT which gives rise to the observed spectral red shift as well as to a reduced calculated electron−hole polarization.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie - Univ.-Prof. Dr. Anna Köhler
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik IX - Spektroskopie weicher Materie
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik IX - Spektroskopie weicher Materie > Lehrstuhl Experimentalphysik IX - Spektroskopie weicher Materie - Univ.-Prof. Dr. Jürgen Köhler
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Professorship Applied Functional Polymers
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Professorship Applied Functional Polymers > Professorship Applied Functional Polymers - Univ.-Prof. Dr. Mukundan Thelakkat
Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Lehrstuhl Experimentalphysik II - Optoelektronik weicher Materie
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
Date Deposited: 28 Feb 2018 07:59
Last Modified: 28 Feb 2018 07:59
URI: https://eref.uni-bayreuth.de/id/eprint/42415