Abstract
Thermodynamics drive crystalline organic molecules to be crystallized at temperatures below their melting point. Even though molecules can form supercooled liquids by rapid cooling, crystalline organic materials readily undergo a phase transformation to an energetically favorable crystalline phase upon subsequent heat treatment. Opposite to this general observation, here, we report molecular design of thermally stable supercooled liquid of diketopyrrolopyrrole (DPP) derivatives and their intriguing shear-triggered crystallization with dramatic optical property changes. Molten DPP8, one of the DPP derivatives, remains as stable supercooled liquid without crystallization through subsequent thermal cycles. More interestingly, under shear conditions, this supercooled liquid DPP8 transforms to its crystal phase accompanied by a 25-fold increase in photoluminescence (PL) quantum efficiency and a color change. By systematic investigation on supercooled liquid formation of crystalline DPP derivatives and their correlation with chemical structures, we reveal that the origin of this thermally stable supercooled liquid is a subtle force balance between aromatic interactions among the core units and van der Waals interactions among the aliphatic side chains acting in opposite directions. Moreover, by applying shear force to a supercooled liquid DPP8 film at different temperatures, we demonstrated direct writing of fluorescent patterns and propagating fluorescence amplification, respectively. Shear-triggered crystallization of DPP8 is further achieved even by living cell attachment and spreading, demonstrating the high sensitivity of the shear-triggered crystallization which is about 6 orders of magnitude more sensitive than typical mechanochromism observed in organic materials.
Original language | English |
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Pages (from-to) | 94-102 |
Number of pages | 9 |
Journal | ACS Central Science |
Volume | 1 |
Issue number | 2 |
DOIs | |
Publication status | Published - May 27 2015 |
Externally published | Yes |
Bibliographical note
Funding Information:The authors thank Dr. J. W. Kampf for assistance on single crystal structure analysis, Dr. S. Seo for assistance on powder XRD characterization, and P. Desai and Dr. R. G. Larson for assistance on the rheometer experiment. This work was supported as part of the Center for Solar and Thermal Energy Conversion, and Energy Frontier Research Center funded by the U.S. Department of Energy (DoE), Office of Science, Basic Energy Sciences (BES) (DE-SC0000957). The work at IMDEA was supported by the Spanish Ministerio de Economiá y Competitividad (MINECO; Project CTQ2011-27317) and by the Campus of International Excellence (CEI) UAM+CSIC. Single crystal X-ray analysis was supported by funding from NSF Grant CHE-0840456 for X-ray instrumentation. The work at IBS was supported by Project Code (IBS-R011-D1).
Funding Information:
The authors thank Dr. J. W. Kampf for assistance on single crystal structure analysis, Dr. S. Seo for assistance on powder XRD characterization, and P. Desai and Dr. R. G. Larson for assistance on the rheometer experiment. This work was supported as part of the Center for Solar and Thermal Energy Conversion, and Energy Frontier Research Center funded by the U.S. Department of Energy (DoE), Office of Science, Basic Energy Sciences (BES) (DE-SC0000957). The work at IMDEA was supported by the Spanish Ministerio de Economi? y Competitividad (MINECO; Project CTQ2011-27317) and by the Campus of International Excellence (CEI) UAM+CSIC. Single crystal X-ray analysis was supported by funding from NSF Grant CHE-0840456 for X-ray instrumentation. The work at IBS was supported by Project Code (IBS-R011-D1).
Publisher Copyright:
© 2015 American Chemical Society.
ASJC Scopus Subject Areas
- General Chemistry
- General Chemical Engineering