Ring-size dependent ratiometric photoluminescence of cyclophane mechanophores
DOKPE
- Thazhathethil, Shakkeeb Tokyo Institute of Technology
- Thuluvanchery, Fazil Salim Tokyo Institute of Technology
- Shimizu, Shohei Tokyo Institute of Technology
- Scarlat, Iulia University of Fribourg
- Clough, Jess M. ORCID University of Fribourg
- Weder, Christoph ORCID University of Fribourg
- Sagara, Yoshimitsu ORCID Tokyo Institute of Technology
- 2024
Published in:
- Journal of Materials Chemistry C. - Royal Society of Chemistry (RSC). - 2024, vol. 12, no. 17, p. 6170-6176
English
Mechanochromic mechanophores which instantly and reversibly change their photoluminescence color
are suitable molecular probes for the in situ visualization and detection of forces that arise in polymers.
Here, we report that the ring size significantly affects the ratiometric photoluminescence of cyclophane
mechanophores whose working mechanism relies on the dissociation of intramolecular charge-transfer
(CT) complexes. We compare three cyclophanes, which each feature a 9,10-bis(phenylethynyl)anthracene
(BPA) group and one pyromellitic diimide (PMDI) in their cycle. These aromatic groups were connected
with linkers of different lengths. In toluene solutions, all cyclophanes display suppressed BPA emission in
comparison to a linear BPA model compound, and a red-shifted emission band associated with a
BPA:PMDI CT complex is observed. The extent of CT formation scales inversely with the length of the
spacers and is thus largest for the smallest cyclophane. The three cyclophanes were covalently
incorporated into segmented polyurethane elastomers, which were processed into thin films. In the
stress-free state, films of the three materials all display roughly equal monomer and CT emission intensity.
Upon uniaxial deformation, this ratio changes in favor of the monomer emission. The changes were very
pronounced for the polymer containing the largest cyclophane, and very small in the material containing
the smallest mechanophore. Thus, the data show clearly that the mechanoresponse of cyclophane
mechanophores strongly depends on the ring size, which dictates to what extent the chromophores can
interact in the absence and presence of an applied force.
are suitable molecular probes for the in situ visualization and detection of forces that arise in polymers.
Here, we report that the ring size significantly affects the ratiometric photoluminescence of cyclophane
mechanophores whose working mechanism relies on the dissociation of intramolecular charge-transfer
(CT) complexes. We compare three cyclophanes, which each feature a 9,10-bis(phenylethynyl)anthracene
(BPA) group and one pyromellitic diimide (PMDI) in their cycle. These aromatic groups were connected
with linkers of different lengths. In toluene solutions, all cyclophanes display suppressed BPA emission in
comparison to a linear BPA model compound, and a red-shifted emission band associated with a
BPA:PMDI CT complex is observed. The extent of CT formation scales inversely with the length of the
spacers and is thus largest for the smallest cyclophane. The three cyclophanes were covalently
incorporated into segmented polyurethane elastomers, which were processed into thin films. In the
stress-free state, films of the three materials all display roughly equal monomer and CT emission intensity.
Upon uniaxial deformation, this ratio changes in favor of the monomer emission. The changes were very
pronounced for the polymer containing the largest cyclophane, and very small in the material containing
the smallest mechanophore. Thus, the data show clearly that the mechanoresponse of cyclophane
mechanophores strongly depends on the ring size, which dictates to what extent the chromophores can
interact in the absence and presence of an applied force.
- Faculty
- Faculté des sciences et de médecine
- Department
- AMI - Chimie des polymères et matériaux
- Language
-
- English
- Classification
- Chemistry
- Other electronic version
- License
-
Rights reserved
- Open access status
- green
- Identifiers
-
- DOI 10.1039/d4tc00244j
- ISSN 2050-7526
- Persistent URL
- https://folia.unifr.ch/unifr/documents/333516
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