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Published on: December 21, 2017
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Directed Polymorphism and Mechanofluorochromism of Conjugated Materials through Weak Non-Covalent Control
Seth A Sharber1, Arielle Mann1, Kuo-Chih Shih2
1Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford, MA 02155, USA.
Journal of Materials Chemistry. C
|November 2, 2020
Summary
Crystal polymorphism in organic optoelectronics is tunable via alkyl chain length in phenylene ethynylenes (PEs). This allows control over violet/green fluorescence and stimuli-responsive behavior, aiding materials discovery.
Area of Science:
- Materials Science
- Organic Optoelectronics
- Crystallography
Background:
- Crystal polymorphism is crucial for tuning material properties in organic optoelectronics.
- Controlling solid-state phases is key to discovering novel materials with desired functionalities.
- Phenylene ethynylenes (PEs) are a versatile class of organic semiconductors.
Purpose of the Study:
- To investigate the structure-dependent polymorphism of ester-terminated three-ring PEs.
- To explore how alkyl chain length influences solid-state fluorescence and stimuli-responsive behavior.
- To establish a design strategy for accessing tunable polymorphs and mechanofluorochromic (MFC) properties.
Main Methods:
- Synthesis of a series of seven ester-terminated three-ring PEs with varying alkyl chain lengths.
- Characterization of solid-state phases using fluorescence spectroscopy.
- Investigation of thermal and mechanofluorochromic (MFC) transitions.
Main Results:
- Alkyl chain length modulates the propensity to form violet or green fluorescent solid phases.
- Short alkyl chains yield both violet and green polymorphs; longer chains favor violet.
- Thermally induced green-to-violet transitions and reversible violet-to-green MFC were observed, with reversion temperature dependent on alkyl chain length.
Conclusions:
- Weak, directional non-covalent interactions enable control over crystal packing and polymorphism in PEs.
- Structural modifications, specifically alkyl chain length, provide a strategy for tuning fluorescence color and stimuli-responsive behavior.
- This approach offers a pathway for designing novel organic optoelectronic materials with tunable properties.
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