Side-chain cholesteric liquid-crystalline elastomers containing azobenzene derivative as cross-linking agent – synthesis and characterisation

ABSTRACT

The cholesteric polysiloxanes (PLQ series) were obtained by reacting cholesteric monomer and phenolic hydroxyl monomer in different ratios with polysiloxanes. The chiral azo-containing polysiloxanes liquid-crystalline elastomers (LCEs) were synthesised by esterifying PLQ series with acyl acid of azo diacid catalysed by 4-dimethylaminopyridine (DMAP). The chemical structures and mesomorphic properties of monomers and polymers were confirmed by conventional spectroscopic methods. The elastomers displayed elastic properties, reversible phase transition and high thermal stability. The T_g values changed irregularly and T_i values decreased at the beginning and then increased afterwards. The chiral azo-LCEs showed colourful textures and a Grandjean texture could be observed, which exhibited a red shift with increasing content of azo moiety. PLQ₂–PLQ₆ exhibited selective reflection in the visible light region, but PLZ₁–PLZ₄ can only observe selective reflection when appropriate mechanical pressure was imposed on the polymers. The PLZ series was carefully investigated by ultra violet–visible spectroscopy.

Graphical Abstract

KEYWORDS:

• Grandjean blue texture
• selective reflection
• chiral
• azo-cross-linking

Acknowledgements

The authors thank Fundamental Research Funds for the Central Universities: [Grant Number N130205001], National Natural Science Foundation: [Grant Number 51273035] and Scientific and Technical Bureau Foundation of Shen Yang City: [Grant Number F16-205-1-03] for financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China: [Grant Number 51273035], Scientific and Technical Bureau Foundation of Shen Yang City: [Grant Number F16-205-1-03] and Fundamental Research Funds for the Central Universities: [Grant Number N130205001].