Main-chain liquid crystalline copolymers: synthesis and comparative study of the mesomorphic properties and non-linear optical properties |
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Authors: | Balamurugan Subramanian Asiqur Rahman Norbani Abdullah Vijay Srinivasan Murugesan Suresh Dhandapani |
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Affiliation: | 1. Solid State Nanodevices Laboratory, Department of Electrical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia;2. Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia;3. Department of Chemistry, Faculty of Science, Anna University, Chennai, India |
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Abstract: | Linear main-chain polymers (P1, P2 and P3) have been synthesised and characterised. The polymers were designed to understand the rigidity of the mesogen’s linking groups and its effect on transition temperature. The liquid crystalline behaviour of these polymers was investigated using polarised optical microscopy and differential scanning calorimetry. All polymers exhibited phase transition on heating and cooling runs. The mesophase stability decreases with the decrease of rigidity of the second mesogen (P2>P1>P3). Similarly, the enthalpy and entropy changes are dependent on the rigidity of the second mesogen (Mesogen B). Polymer P1 undergoes photoisomerisation under UV-visible light irradiation and it attains a photo-stationary state at 275 s. This provides an opportunity to investigate the third-order non-linear optical properties. The non-linear behaviour of polymer P1 in chloroform presents a distinct deviation in a different concentration, where polymer P1 also exhibits a negative non-linear refractive index. Thus, polymer P1 can be used as a potential candidate for optical device applications such as optical limiters. |
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Keywords: | Main-chain liquid crystalline polymer azobenzene liquid crystalline polymer photoisomerisation nematic phase NLO |
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