Effect of iron-iron oxide particles on the rate of isomerization of azobenzene moieties in polymeric liquid crystals at
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ORIGINAL CONTRIBUTION
Effect of iron-iron oxide particles on the rate of isomerization of azobenzene moieties in polymeric liquid crystals at air-water interface Raghavendra1 · Satyam Kumar Gupta2,3 · Bharat Kumar1 Received: 10 August 2020 / Revised: 22 October 2020 / Accepted: 23 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract We have studied the effect of iron-iron oxide particles on the trans-cis isomerization of azobenzene moieties in the novel polyethylene glycol itaconate-azobenzene based side chain liquid crystalline polymer (PEGIA). Langmuir monolayers of the PEGIA molecules are spread at air-water interface, with water subphase containing different concentrations of iron-iron oxide particles. The kinetics of the isomerization of azobenzene moieties in the polymer was studied by surface manometry technique. We find that the presence of iron-iron oxide particles in the subphase affects the rate constant of trans-cis photoisomerization and it decreases exponentially as a function of concentration of particles in the subphase. The critical concentration of iron-iron oxide particles above which the rate constant of photoisomerization negligibly changed was found to be about 2.468 μg cm−3 . Keywords Polymeric liquid crystals · Langmuir monolayer · Kinetics of trans-cis isomerization
Introduction The study of polymeric liquid crystals have gained tremendous interest not only because of their unique properties but also due to applications. The functionalized polymeric liquid crystals can exhibit reversible response to the external stimuli, such as temperature [1, 2], pH [1, 3], magnetic field [4], electric field [4] and electromagnetic radiation [5]. These materials find applications in drug delivery [6], sensors [6–8] etc. In particular, polymeric liquid crystals containing azobenzene moiety are of interest because their molecular conformation can be maneuvered from trans to cis state and vice-versa by isomerization. The isomerization process can be controlled by shining light of appropriate Bharat Kumar
[email protected] 1
Department of Physics, Central University of Karnataka, Kadaganchi, Kalaburagi District, Karnataka, 585367, India
2
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru, Karnataka, 560012, India
3
Present address: Department of Chemistry, Avvaiyar Government College For Women, Dr. Ambedkar Street, Karaikal, Puducherry (U.T.), 609602, India
wavelength [9] or by applying the electric field [10–12]. The excited cis state of molecules can isomerize back to trans state by thermal isomerization. The light induced maneuverability make azobenzene molecules potential candidates for various applications. Azobenzene moieties in biological molecules such as proteins can also be used for the spatial and temporal control of a variety of biological processes through illumination of light [13–15]. The photoisomerization from trans-cis state induces the rotating mechanism while thermal cis-trans isomerization follows an inversion me
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