Dynamics of Photoinduced Orientation of Nonpolar Azobenzene Groups in Polymer Films. Characterization of the Cis Isomers by Visible and FTIR Spectroscopies
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Bibliographic record
Abstract
To better characterize the cis state and the reorientation processes in polymers containing azobenzene groups, the in situ dynamics of photoinduced orientation of a polymer with azobenzene groups bearing no donor and acceptor substituents such as poly[4-[2-(methacryloyloxy)ethyl]azobenzene] polymer (pMEA) was carried out using real-time UV−vis and infrared spectroscopies. Thin films of pMEA were irradiated at 488 nm with either linearly or circularly polarized light ( I pump = 10 mW/cm 2 ). The different mechanisms occurring during the photoisomerization cycles were revealed by following the time dependence of the normalized average absorbance ( T 0 ) and the normalized linear dichroism ( T 2 ) during the orientation (laser on) and relaxation (laser off) periods. Therefore, the normalized average absorbance has allowed an estimation of the cis isomer fraction ( f cis ) at the photostationary state. The photoisomerization is more efficient when the film is irradiated using a circularly polarized light ( f cis = 0.15) than using linearly polarized light ( f cis = 0.11). The cis state has been characterized for the first time in azopolymers by infrared spectroscopy using a band at 1515 cm -1 characteristic of the cis isomers. The time dependence of the intensity of this band during the relaxation period has shown that the cis state is very stable and has a lifetime of about 12 h. Finally, a significant dichroism of the trans and cis isomers has been observed when the films were irradiated with a linearly polarized light.
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Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
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