Browsing by Author "Lin, Hong Cheu"

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Influence of terminal substituent on non-linear S-shaped oligomers consisting of azobenzene moieties at the peripheral arm: Synthesis, characterisation and phase transition behaviour
(2017-01-01)
Yeap, Guan-Yeow
;
Osman, Faridah
;
Ito, Keisuke
;
Takeuchi, Daisuke
;
Lin, Chien-Min
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.
Liquid crystalline non-linear S-shaped oligomers consisting of azobenzene and biphenylene units: synthesis, characterisation and influence of central spacer
(2017-01-01)
Osman, Faridah
;
Yeap, Guan-Yeow
;
Maeta, Nobuyuki
;
Ito, Masato M.
;
Lin, Chien-Min
A series of non-linear S-shaped liquid crystal oligomers wherein the molecule consists of biphenylene moiety as a central core unit and two symmetrical side arms azobenzene moieties joined to catechol as a linkage group have been successfully synthesised and characterised. The members in this series possess different inner spacer with carbon number n ranging from 4 to 9 while the outer spacer length located in azobenzene moieties are remains unaltered. The members with even parity exhibit monotropic phase, whereas homologues with odd parity display enantiotropic phase. The appearance of nematic, smectic A and smectic B phases was validated with texture observation under polarised light and X-ray diffraction (XRD). The XRD study on the S-shaped oligomer indicates that the arrangement of smectic phase exists as an intercalated structure. The S-shaped oligomer shows photoisomerisation properties in solution whereby the trans to cis isomerisation for this molecule is accomplished 1140 s, whereas reverse process under thermal back reaction occurred in 4620 min. [GRAPHICS] .
Mesomorphic behavior of new benzothiazole liquid crystals having Schiff base linker and terminal methyl group
(2012-07-01)
Ha, Sie Tiong
;
Foo, Kok Leei
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Lin, Hong Cheu
;
Ito, Masato M.
;
Abe, Kazuma
"A homologous series of heterocycles, 6-methyl-2-(4-alkoxybenzylidenamino)benzothiazoles, were synthesized and characterized using FT-IR, H-1 and C-13 NMR and mass spectrometric analysis. Enantiotropic nematic phase was observed for shorter members. Smectic A phase only emerged from octyloxy derivative onwards. The terminal methyl group at the benzothiazole fragment and the Schiff base linkage influenced the mesomorphic behavior of the present series. (C) 2012 Sie Tiong Ha. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved."
New mesogenic Schiff base esters comprising benzothiazole moiety: Synthesis and mesomorphic properties
(2009-09-01)
Ha, Sie Tiong
;
Koh, Teck Ming
;
Yeap, Guan Yeow
;
Lin, Hong Cheu
;
Beh, Jun Kit
A homologous series of Schiff base esters, 6-methoxy-2-(2-hydroxy-4-alkanoyloxybenzylidenamino)benzothiazoles, comprising a benzothiazole moiety as the core was synthesized. All the members of this series exhibited an enantiotropic nematic phase. The azomethine linkage along with the lateral hydroxyl and terminal methoxyl groups were found to exert an effect on the mesomorphic properties. (C) 2009 Sie Tiong Ha. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Synthesis and Characterization of Novel Low-Bandgap Triphenylamine-Based Conjugated Polymers with Main-Chain Donors and Pendent Acceptors for Organic Photovoltaics
(2010-12-15)
Sahu, Duryodhan
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Padhy, Harihara
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Patra, Dhananjaya
;
Huang, Jen Hsien
;
Chu, Chih Wei
A series of novel low bandgap triphenylamine based conjugated polymers (PCAZCN PPTZCN and PDTPCN) consisting of different electron rich donor main chains (N alkyl 2 7 carbazole phenothiazine and cyclopentadithinopyrol respectively) as well as cyano and dicyano vinyl electron acceptor pendants were synthesized and developed for poly mer solar cell applications The polymers covered broad absorption spectra of 400-800 nm with narrow optical band gaps ranging 1 66-1 72 eV The highest occupied molecular or bital and lowest unoccupied molecular orbital levels of the polymers measured by cyclic voltammetry were found in the range of -5 12 to -532 V and -345 to -355 eV respectively Under 100 mW/cm(2) of AM 1 5 white light illumination bulk heterojunction photovoltaic devices composing of an active layer of electron donor polymers (PCAZCN PPTZCN and PDTPCN) blended with electron acceptor [6 6] phenyl C(61) butync acid methyl ester or [6 6] phenyl C(71) butyric acid methyl ester (PC(71)BM) in different weight ratios were investigated The photovoltaic device containing donor PCAZCN and acceptor PC(71)BM in 1 2 weight ratio showed the highest power conversion efficiency of 1 28% with V(oc) = 0 81 V J(sc) = 493 mA/cm(2) and fill factor = 32 1% (c) 2010 Wiley Periodicals Inc J Polym Sci Part A Polym Chem 48 5812-5823 2010
Synthesis and mesomorphic evaluation of new calamitic liquid crystals containing benzothiazole core
(2011-05-01)
Koh, Teck Ming
;
Ha, Sie Tiong
;
Lee, Teck Leong
;
Lee, Siew Ling
;
Yeap, Guan Yeow
The design and synthesis of new calamitic benzothiazole-based liquid crystals, 2[4-(4-alkyloxybenzoyloxy)-phenyl]benzothiazoles are presented. The target compound was characterized using spectroscopic techniques, such as FT-IR, NMR ((1)H and (13)C), microanalysis and EI-MS. The liquid crystalline behaviours of these compounds were thoroughly examined by differential scanning calorimetry and polarizing optical microscope techniques. These materials exhibited enantiotropic nematic phase with high thermal stability (> 168 degrees C). Smectic A phase starts to emerge as monotropic (metastable) phase from C10 member and changes into enantiotropic (stable) phase from C12 and persists up to C16 members. (C) 2010 Sie Tiong Ha. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Synthesis and mesomorphic properties of new Schiff base esters with different alkyl chains
(2009-07-01)
Ha, Sie Tiong
;
Ong, Lay Khoon
;
Ong, Siew Teng
;
Yeap, Guan Yeow
;
Wong, Joanna Pik Wan
A new series of Schiff base esters, 4-(dimethylamino)benzylidene-4'-alkanoyloxyanilines containing even number of carbons at the end group of the molecules (C(n-1)H(2n-1)COO, n = 6, 8, 10, 12, 14, 16, 18) were synthesized. The present compounds were monotropic liquid crystals. It was also found that the end groups of the molecules had effect on the mesomorphic properties. (C) 2009 Sie Tiong Ha. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Synthesis and mesomorphic properties of Schiff base esters possessing terminal chloro substituent
(2010-06-01)
Ha, Sie Tiong
;
Ong, Lay Khoon
;
Lee, Siew Ling
;
Lin, Hong Cheu
;
Win, Yip Foo
A homologous series of Schiff base esters, 4-chlorobenzylidene-4'-n-alkanoyloxyanilines, containing even number of carbons at the end groups of the molecules (C(n-1)H(2n-1)COO-, n = 4, 6, 8, 10, 12, 14, 16) were synthesized. The mesomorphic properties were investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). It was found that the end groups of the molecules had an effect on the mesomorphic properties. n-Butanoyloxy was found non-mesogenic, whilst n-hexanoyloxy exhibited monotropic smectic phase. The higher members in this homologous series were enantiotropic smectogens. (C) 2010 Sie Tiong Ha. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.