Main-chain side-chain combined liquid crystalline polymers bearing azobenzene and biphenyl-based mesogens – segregation of the mesogens within two distinct layers. Issue 7 (15th July 2022)

• Record Type: Journal Article
• Authors: Orodepo, Gabriel Ogunsola; Bej, Sujoy; Gowd, E Bhoje; Ramakrishnan, S.
• Is Part Of: Liquid crystals. Volume 49:Issue 7/9(2022)
• Page Start: 1020
• Page End: 1030
• Publication Date: 2022-07-15
• Subjects: Liquid crystalline polymer -- pendant mesogen -- mesogen segregation -- zigzag folded chains; Liquid crystals -- Periodicals; 548.905
• DOI: 10.1080/02678292.2022.2046882
• Languages: English
• ISSNs: 0267-8292

Abstract

ABSTRACT: Two different mesogenic units, namely biphenyl and azobenzene, were installed centrally within the polymer backbone and pendant alkylene segments; the purpose was to examine if chain folding of the backbone occurs so as to segregate the azobenzene and biphenyl units in adjacent layers of a smectic-type ordering . Two sets of isomeric main-chain side-chain liquid crystalline polymers (MCSC-LCPs), namely SC-AzoC x -MC-BPC x and SC-BPC x -MC-AzoC x ( x =6 or 10), were synthesised; the former series has biphenyl in the backbone and azobenzene in the side-chain, while their locations are switched in the latter. It was observed that all four polymers were semicrystalline at room temperature and exhibited a smectic mesophase upon melting. DSC and X-ray scattering studies revealed that switching the locations of the azobenzene and biphenyls had little effect on; the phase transition temperatures and smectic layer spacings. A second series, namely SC-AzoC x -MC-BPC y and SC-BPC x -MC-AzoC y, where the length of alkylene spacers in the side-chain (C x ) and backbone (C y ) is different, was also studied; this was done to examine the influence of unequal alkylene segment lengths on the mesophase structure and interlayer spacing, and importantly, whether the zigzag folding-induced formation of a layered structure is retained, despite their unsymmetrical nature. Graphical abstract: uf0001