Synthesis of bent-shaped azobenzene main-chain polymers for photo-switching properties

This work presents the synthesis of the new bent-core polymers with siloxane units connected to the one side of azobenzene units. The structure of siloxane-based azobenzene bent-core polymers, 7a-c, was elucidated by spectral analysis (nuclear magnetic resonance and Fourier-transform infrared spectr...

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Published in:Journal of macromolecular science. Part A, Pure and applied chemistry Pure and applied chemistry, 2024-01, Vol.61 (1), p.40-52
Main Authors: Rahman, Md Lutfor, Xin Ting, Tang, Sarjadi, Mohd Sani, Arshad, Sazmal Effendi, Soloi, Sabrina, Jamain, Zuhair, Abd Majid, Mohd Hafiz, Hedge, Gurumurthy
Format: Article
Language:English
Subjects:
Azo compounds
Azobenzene
bent-core
Chains (polymeric)
Chemical synthesis
Degree of polymerization
Fourier transforms
Gel chromatography
Infrared analysis
Infrared spectroscopy
Isomerization
Liquid crystals
main-chain polymers
Monomers
NMR
Nuclear magnetic resonance
Optical microscopy
photo-switching
Polydispersity
Polymerization
Polymers
siloxane
Siloxanes
Spectrum analysis
Switching
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Summary:This work presents the synthesis of the new bent-core polymers with siloxane units connected to the one side of azobenzene units. The structure of siloxane-based azobenzene bent-core polymers, 7a-c, was elucidated by spectral analysis (nuclear magnetic resonance and Fourier-transform infrared spectroscopy). The results of gel permeation chromatography suggested that all polymers (7a-c) showed polydisperse (polydispersity index >1). Besides, the extent of polymerization in the following order: 7a > 7b > 7c, where the degree of polymerization values were 7, 8 and 11, respectively. Polarizing optical microscopy revealed that the bent-core liquid crystal (BCLC) monomers, 6a and 6b, displayed the smectic A phase, whereas BCLC monomer 6c and all siloxane-based main-chain polymers (MCPs) (7a-c) were crystalline in nature. The result of ultraviolet-visible spectroscopy demonstrated that all MCPs (7a-c) exhibited strong photoisomerization behavior in solution. All polymers (7a-c) showed trans to cis isomerization in about 200 s, whereas the reverse process required much longer times ranging from 400 to 520 min in solution. The photo-switching study on azobenzene containing polymers stated that the effect of alkyl chain length and type of central core units on trans to cis isomerization were negligible. In contrast, both parameters influence the cis to trans process in which the photo-switching behavior of these materials may be primarily suitably exploited in the field of photo-induced phenomenon. Time dependence photoisomerization curve of a) trans isomer (7a-c) showing the effect of UV illumination at 365 nm wavelength, which take time for trans to cis isomerization in about 200s, and b) cis isomer (7a-c) showing the thermal back relaxation time, the reverse process required much longer times ranging from 400-520 min in solution
ISSN:1060-1325
1520-5738
DOI:10.1080/10601325.2023.2287033