Synthesis and microwave dielectric properties of polyphenylene liquid crystal compounds with lateral substitution by methyl and fluorine
| Autor: | Zhang Zhiyong, Cai Xionghui, Chen Hongmei, Manman Liu, Guan Jintao, Liu Haohao, Gao Shihan, Xiangru Wang, Qiao Junfei |
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| Rok vydání: | 2021 |
| Předmět: |
Materials science
Microwave dielectric properties 010405 organic chemistry Physics::Optics chemistry.chemical_element 02 engineering and technology General Chemistry Dielectric 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences 0104 chemical sciences Physics::Fluid Dynamics Condensed Matter::Soft Condensed Matter chemistry Chemical engineering Liquid crystal Lateral substitution Fluorine General Materials Science 0210 nano-technology |
| Zdroj: | Liquid Crystals. 48:1581-1592 |
| ISSN: | 1366-5855 0267-8292 |
| DOI: | 10.1080/02678292.2021.1891477 |
| Popis: | Nematic liquid crystals are promising materials for microwave communication owing to their continuous tunability as dielectrics and wide frequency range selection. However,conventional liquid crystals exhibit large dielectric loss and high freezing point, hindering their research and application in microwave communication. in this paper,14 novel liquid crystal polyphenylene compounds with lateral methyl substitute were synthesised. Their structures were characterized by IR, NMR,MS and the elemental analyses. Their mesogenic properties were analyzed by POM and DSC. The dielectric properties in microwave frequencies(10-35 GHz)of eight target compounds (6a,7b,8a~8e) with LC matrix were obtained by extrapolation and perturbation techniques. The results show that i. fluorinated polyphenylene compounds with lateral methyl generally exhibited low melting points (���75��C), ii. compounds with isothiocyanate group yielded high birefringence 0.385-0.441, iii. compounds based on quaterphenyl displayed a wide temperature range of nematic phase, and iv. the maximum dielectric loss of compounds 6e,8c,8e are less than 6.51��10-3,which are better than those of using fluorine replace the methyl group derivative. Therefore, the proposed approach can effectively reduce dielectric loss,reduce the melting temperature, improve the dielectric properties of liquid crystal materials for microwave communication. |
| Databáze: | OpenAIRE |
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