標題: Influence of terminal substituent on non-linear S-shaped oligomers consisting of azobenzene moieties at the peripheral arm: Synthesis, characterisation and phase transition behaviour
作者: Yeap, Guan-Yeow
Osman, Faridah
Ito, Keisuke
Takeuchi, Daisuke
Lin, Chien-Min
Lin, Hong Cheu
材料科學與工程學系
Department of Materials Science and Engineering
關鍵字: S-shaped mesogen;monotropic;nematic;smectic A;smectic B;monolayer
公開日期: 1-Jan-2017
摘要: A series of symmetrical S-shaped mesogens based on 4,4-bis-(6-bromohexyloxy)biphenyl as a central unit containing two 2-{6-[4-(4-substitutedphenylazo)phenoxy]hexyloxy}phenol as side-chain groups has been successfully synthesised. The terminal substituent was varied from halogen (X=F, Cl, Br and I) to non-halogen (X=C2H5 and OC2H5). The oligomers with C2H5 and OC2H5 substituents exhibit predominantly the monotropic nematic (N) phase. The OC2H5-containing derivatives possess long-range stability of N phase than its C2H5-containing analogue in which it has small range of N phase stability. As for halogen-containing analogues, oligomer with F exhibits monotropic N phase whilst oligomers with Cl and Br exhibit monotropic N and smectic A (SmA) phases. In addition, homologue with Br shows additional phase which is smectic B (SmB) phase upon further cooling. However, the oligomers in which F, Cl and Br were substituted by I exhibits purely monotropic SmA and SmB phases. X-ray diffraction measurements reveal that the smectic phase is inclined to the monolayer structure.
URI: http://dx.doi.org/10.1080/02678292.2016.1246677
http://hdl.handle.net/11536/145569
ISSN: 0267-8292
DOI: 10.1080/02678292.2016.1246677
期刊: LIQUID CRYSTALS
Volume: 44
起始頁: 809
結束頁: 821
Appears in Collections:Articles