Non-linear disulphide-centred S-shaped oligomers with inner and outer spacers connected by aromatic azo moieties

ABSTRACT

The synthesis and characterisation of a series of non-linear S-shaped oligomers [bis-n-(2-(6-(4-{4-acetylphenylazo}phenoxy)hexyloxy)phenoxy)alkyl]disulphide are reported. The length of the two outer spacers for this series are retained at n₁ = 6 while the length of the inner spacer, n₂, is varied from four to nine methylene units. All oligomers exhibit monotropic nematic phase except compound with butyl spacer which is non-mesogenic. The odd-even effect can be verified at the I-N transition temperature wherein the oligomers with odd-numbered inner spacers display higher transition temperature in comparison to its even-membered analogous compounds. The molecules in this series exhibit prominent photoisomerisation behaviour that can be validated by the rate of conversion from trans to cis (1620 s) and vice versa (3120 min).

Graphical abstract

KEYWORDS:

• Non-linear
• central disulphide
• inner and outer spacers
• odd-even effect
• photoisomerisation

Acknowledgements

The main author (G.-Y. Yeap) would like to thank Ministry of Higher Education Malaysia for Fundamental Research Grant Scheme (FRGS 2020-1) with Project Code: FRGS/1/2020/STG04/USM/01/2. All researchers are also grateful for the research funding under International Collaborative Research by Soka University (Japan).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Fundamental Research Grant Scheme [FRGS/1/2020/STG04/USM/01/2].