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Title: Non-covalent planarizing interactions yield highly ordered and thermotropic liquid crystalline conjugated polymers

Journal Article · · Materials Horizons
DOI: https://doi.org/10.1039/D3MH01974H · OSTI ID:2341926
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3];  [2]; ORCiD logo [1]; ORCiD logo [1];  [4];  [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [1]
  1. Georgia Institute of Technology, Atlanta, GA (United States)
  2. Univ. of Illinois at Urbana-Champaign, IL (United States)
  3. Univ. of Arizona, Tucson, AZ (United States)
  4. Wake Forest Univ., Winston-Salem, NC (United States)

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.

Research Organization:
Georgia Institute of Technology, Atlanta, GA (United States)
Sponsoring Organization:
USDOE; USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Grant/Contract Number:
EE0009524
OSTI ID:
2341926
Journal Information:
Materials Horizons, Journal Name: Materials Horizons Journal Issue: 14 Vol. 11; ISSN 2051-6355; ISSN 2051-6347
Publisher:
Royal Society of ChemistryCopyright Statement
Country of Publication:
United States
Language:
English

References (85)

Photoinduced Anisotropic Supramolecular Assembly and Enhanced Charge Transport of Poly(3-hexylthiophene) Thin Films journal April 2014
Using Molecular Design to Increase Hole Transport: Backbone Fluorination in the Benchmark Material Poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno[3,2‐ b ]‐thiophene (pBTTT) journal October 2015
Contact Resistance in Organic Field‐Effect Transistors: Conquering the Barrier journal September 2019
Tuning the Mechanical and Electric Properties of Conjugated Polymer Semiconductors: Side‐Chain Design Based on Asymmetric Benzodithiophene Building Blocks journal August 2022
The Effects of Side Chains on the Charge Mobilities and Functionalities of Semiconducting Conjugated Polymers beyond Solubilities journal September 2019
Organic Electronics Picks Up the Pace: Mask‐Less, Solution Processed Organic Transistors Operating at 160 MHz journal January 2021
Measurements of Ambipolar Seebeck Coefficients in High-Mobility Diketopyrrolopyrrole Donor-Acceptor Copolymers journal August 2017
Will We See Gigahertz Organic Transistors? journal January 2018
Elucidating the Role of Water‐Related Traps in the Operation of Polymer Field‐Effect Transistors journal June 2021
Critical Role of Polymer Aggregation and Miscibility in Nonfullerene‐Based Organic Photovoltaics journal January 2020
Regiosymmetric Poly(dialkylphenylenedioxythiophene)s: Electron-Rich, Stackable π-Conjugated Nanoribbons journal January 2007
Conformation Control of Conjugated Polymers journal September 2020
High-Mobility Conjugated Polymers Based on Fused-Thiophene Building Blocks journal January 2011
Alignment of Organic Conjugated Molecules for High‐Performance Device Applications journal May 2022
Optimizing the self‐assembly of conjugated polymers and small molecules through structurally programmed non‐covalent control journal July 2021
Liquid crystalline conjugated polymers and their applications in organic electronics journal June 2009
The Polymer Physics of Multiscale Charge Transport in Conjugated Systems journal August 2019
Liquid Crystal Ordering on Conjugated Polymers Film Morphology for High Performance journal November 2019
Boosting thermoelectric performance of conjugated polymers via interchain molecular docking: Significance of highly crystalline and percolated morphology journal July 2023
Electrochromic polymer with asymmetric substituents – Inhibit aggregation and modify respond speed journal January 2022
Investigation of the thermoelectric response in conducting polymers doped by solid-state diffusion journal March 2019
Interface engineering to enhance charge injection and transport in solution-deposited organic transistors journal November 2017
Controlling morphology and microstructure of conjugated polymers via solution-state aggregation journal January 2023
Solvent-assisted conformational interconversion of an organic semiconductor with multiple non-covalent interactions journal March 2022
Covalent and Noncovalent Approaches to Rigid Coplanar π-Conjugated Molecules and Macromolecules journal March 2019
Ordering of Poly(3-hexylthiophene) in Solutions and Films: Effects of Fiber Length and Grain Boundaries on Anisotropy and Mobility journal May 2016
Noncovalent Close Contacts in Fluorinated Thiophene–Phenylene–Thiophene Conjugated Units: Understanding the Nature and Dominance of O···H versus S···F and O···F Interactions with Respect to the Control of Polymer Conformation journal June 2019
Polymer Semiconductors: Synthesis, Processing, and Applications journal May 2023
From Solution to Thin Film: Molecular Assembly of π-Conjugated Systems and Impact on (Opto)electronic Properties journal June 2023
Effect of Regioregularity on Charge Transport and Structural and Excitonic Coherence in Poly(3-hexylthiophene) Nanowires journal June 2015
Controlling Intramolecular Conformation through Nonbonding Interaction for Soft-Conjugated Materials: Molecular Design and Optoelectronic Properties journal August 2016
Direct Observation of Two-Step, Stratified Crystallization and Morphology in Conjugated Polymer Thin Films journal April 2023
Monitoring Molecular Ordering of a Conjugated Polymer: PBTTT during Conformational Evolution journal August 2023
Tuning Orientational Order of Highly Aggregating P(NDI2OD-T 2 ) by Solvent Vapor Annealing and Blade Coating journal December 2018
Molecular Design Approach for Directed Alignment of Conjugated Polymers journal August 2019
Fast-Coating Process Based on Elongated Rodlike Preaggregate for Highly Oriented Thin Film of Donor–Acceptor π-Conjugated Polymer journal October 2022
Randomly Distributed Conjugated Polymer Repeat Units for High-Efficiency Photovoltaic Materials with Enhanced Solubility and Processability journal November 2018
Effect of Alkyl Side Chain Length on Doping Kinetics, Thermopower, and Charge Transport Properties in Highly Oriented F 4 TCNQ-Doped PBTTT Films journal January 2019
Structural Transition and Interdigitation of Alkyl Side Chains in the Conjugated Polymer Poly(3-hexylthiophene) and Their Effects on the Device Performance of the Associated Organic Field-Effect Transistor journal December 2019
Nucleobase-Functionalized Poly(alkylthiophene)s: One-Pot, Sequential Direct Arylation Polymerization and Deprotection, and Surface Modification for Oil–Water Separations journal January 2021
Understanding Comparable Charge Transport Between Edge-on and Face-on Polymers in a Thiazolothiazole Polymer System journal April 2019
Organic Photovoltaic Performance Resiliency: Role of Molecular Weight in a PM7 Derivative journal July 2023
Amyloid Fibrils Length Controls Shape and Structure of Nematic and Cholesteric Tactoids journal December 2018
Influence of Side Chain Interdigitation on Strain and Charge Mobility of Planar Indacenodithiophene Copolymers journal September 2022
Importance of C 2 Symmetry for the Device Performance of a Newly Synthesized Family of Fused-Ring Thiophenes journal March 2010
Systematic Investigation of Isoindigo-Based Polymeric Field-Effect Transistors: Design Strategy and Impact of Polymer Symmetry and Backbone Curvature journal May 2012
Controlling Conformations of Conjugated Polymers and Small Molecules: The Role of Nonbonding Interactions journal May 2013
Influence of Side-Chain Regiochemistry on the Transistor Performance of High-Mobility, All-Donor Polymers journal October 2014
Achieving Record-Efficiency Organic Solar Cells upon Tuning the Conformation of Solid Additives journal July 2022
Beyond Conformational Control: Effects of Noncovalent Interactions on Molecular Electronic Properties of Conjugated Polymers journal October 2021
Characterization of Charge-Carrier Transport in Semicrystalline Polymers: Electronic Couplings, Site Energies, and Charge-Carrier Dynamics in Poly(bithiophene- alt -thienothiophene) [PBTTT] journal January 2013
Repeat unit symmetry effects on the physical and electronic properties of processable, electrically conducting, substituted poly[1,4-bis(2-thienyl)phenylenes] journal January 1992
Molecular Basis of Mesophase Ordering in a Thiophene-Based Copolymer journal August 2008
Controlling the Orientation of Terraced Nanoscale “Ribbons” of a Poly(thiophene) Semiconductor journal March 2009
Approaching disorder-free transport in high-mobility conjugated polymers journal November 2014
Mobility overestimation due to gated contacts in organic field-effect transistors journal March 2016
Deposition and drying dynamics of liquid crystal droplets journal May 2017
Liquid-crystalline semiconducting polymers with high charge-carrier mobility journal March 2006
A general relationship between disorder, aggregation and charge transport in conjugated polymers journal August 2013
Critical assessment of charge mobility extraction in FETs journal December 2017
A simple and robust approach to reducing contact resistance in organic transistors journal December 2018
Suppressing bias stress degradation in high performance solution processed organic transistors operating in air journal April 2021
A molecular descriptor of intramolecular noncovalent interaction for regulating optoelectronic properties of organic semiconductors journal May 2023
Charge transport in high-mobility conjugated polymers and molecular semiconductors journal April 2020
Confinement-induced liquid crystalline transitions in amyloid fibril cholesteric tactoids journal March 2018
Combined Microscopy, Calorimetry and X-ray Scattering Study of Fluorinated Dimesogens journal October 2017
The Dependency of Nematic and Twist-bend Mesophase Formation on Bend Angle journal November 2016
To bend or not to bend – are heteroatom interactions within conjugated molecules effective in dictating conformation and planarity? journal January 2016
Synthesis of a soluble adenine-functionalized polythiophene through direct arylation polymerization and its fluorescence responsive behavior journal January 2020
Understanding, quantifying, and controlling the molecular ordering of semiconducting polymers: from novices to experts and amorphous to perfect crystals journal January 2022
Synthesis and optoelectronic properties of benzodithiophene-based conjugated polymers with hydrogen bonding nucleobase side chain functionality journal January 2020
Morphological design strategies to tailor out-of-plane charge transport in conjugated polymer systems for device applications journal January 2021
An insight into the role of side chains in the microstructure and carrier mobility of high-performance conjugated polymers journal January 2021
Gaining control over conjugated polymer morphology to improve the performance of organic electronics journal January 2022
Impact of backbone linkage positions on the molecular aggregation behavior of polymer photovoltaic materials journal January 2022
Non-covalent interactions (NCIs) in π-conjugated functional materials: advances and perspectives journal January 2023
Additive-free molecular acceptor organic solar cells processed from a biorenewable solvent approaching 15% efficiency journal January 2023
On the schlieren texture in nematic and smectic liquid crystals journal January 1972
Undoped polythiophene field-effect transistors with mobility of 1cm2V−1s−1 journal December 2007
Tutorial: Organic field-effect transistors: Materials, structure and operation journal August 2018
Liquid crystalline tactoids: ordered structure, defective coalescence and evolution in confined geometries
  • Wang, Pei-Xi; MacLachlan, Mark J.
  • Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 376, Issue 2112 https://doi.org/10.1098/rsta.2017.0042
journal December 2017
Bilayer smectic order in a mixture of polyphilic liquid crystals journal April 1997
Direct observation of charge-induced π -electronic structural changes in a conjugated polymer journal October 1989
Tuning conformation, assembly, and charge transport properties of conjugated polymers by printing flow journal August 2019
H- and J-Aggregate Behavior in Polymeric Semiconductors journal April 2014