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Sabury S, Xu Z, Saiev S, Davies D, Österholm AM, Rinehart JM, Mirhosseini M, Tong B, Kim S, Correa-Baena JP, Coropceanu V, Jurchescu OD, Brédas JL, Diao Y, Reynolds JR. Non-covalent planarizing interactions yield highly ordered and thermotropic liquid crystalline conjugated polymers. MATERIALS HORIZONS 2024. [PMID: 38686501 DOI: 10.1039/d3mh01974h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Controlling the multi-level assembly and morphological properties of conjugated polymers through structural manipulation has contributed significantly to the advancement of organic electronics. In this work, a redox active conjugated polymer, TPT-TT, composed of alternating 1,4-(2-thienyl)-2,5-dialkoxyphenylene (TPT) and thienothiophene (TT) units is reported with non-covalent intramolecular S⋯O and S⋯H-C interactions that induce controlled main-chain planarity and solid-state order. As confirmed by density functional theory (DFT) calculations, these intramolecular interactions influence the main chain conformation, promoting backbone planarization, while still allowing dihedral rotations at higher kinetic energies (higher temperature), and give rise to temperature-dependent aggregation properties. Thermotropic liquid crystalline (LC) behavior is confirmed by cross-polarized optical microscopy (CPOM) and closely correlated with multiple thermal transitions observed by differential scanning calorimetry (DSC). This LC behavior allows us to develop and utilize a thermal annealing treatment that results in thin films with notable long-range order, as shown by grazing-incidence X-ray diffraction (GIXD). Specifically, we identified a first LC phase, ranging from 218 °C to 107 °C, as a nematic phase featuring preferential face-on π-π stacking and edge-on lamellar stacking exhibiting a large extent of disorder and broad orientation distribution. A second LC phase is observed from 107 °C to 48 °C, as a smectic A phase featuring sharp, highly ordered out-of-plane lamellar stacking features and sharp tilted backbone stacking peaks, while the structure of a third LC phase with a transition at 48 °C remains unclear, but resembles that of the solid state at ambient temperature. Furthermore, the significance of thermal annealing is evident in the ∼3-fold enhancement of the electrical conductivity of ferric tosylate-doped annealed films reaching 55 S cm-1. More importantly, thermally annealed TPT-TT films exhibit both a narrow distribution of charge-carrier mobilities (1.4 ± 0.1) × 10-2 cm2 V-1 s-1 along with a remarkable device yield of 100% in an organic field-effect transistor (OFET) configuration. This molecular design approach to obtain highly ordered conjugated polymers in the solid state affords a deeper understanding of how intramolecular interactions and repeat-unit symmetry impact liquid crystallinity, solution aggregation, solution to solid-state transformation, solid-state morphology, and ultimately device applications.
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Affiliation(s)
- Sina Sabury
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
| | - Zhuang Xu
- Department of Chemical and Biomolecular Engineering, Department of Chemistry, Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, USA
| | - Shamil Saiev
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ 85721-0041, USA
| | - Daniel Davies
- Department of Chemical and Biomolecular Engineering, Department of Chemistry, Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, USA
| | - Anna M Österholm
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
| | - Joshua M Rinehart
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
| | - Motahhare Mirhosseini
- Department of Physics and Center for Functional Materials, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Benedict Tong
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
| | - Sanggyun Kim
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Juan-Pablo Correa-Baena
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Veaceslav Coropceanu
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ 85721-0041, USA
| | - Oana D Jurchescu
- Department of Physics and Center for Functional Materials, Wake Forest University, Winston-Salem, NC 27109, USA
| | - Jean-Luc Brédas
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, AZ 85721-0041, USA
| | - Ying Diao
- Department of Chemical and Biomolecular Engineering, Department of Chemistry, Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, USA
| | - John R Reynolds
- School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Tech Polymer Network, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
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