Cholesteric liquid crystalline polysiloxanes containing furan ring with selective reflection - synthesis and properties

In this paper, first series of liquid crystal polymers (PF) synthesised by hydrosilylation of monomer containing furan group (MA), monomer containing cholesterol group (MB), monomer containing D (+)-camphoric acid group (MC) and monomer containing cyano-group (MD), catalysed by platinum catalyst. Another series of liquid crystal polymers (EF) is synthesised by the Dies-Alder reaction of the former series and cross-linker containing bismaleimide group. The results of Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance(H-1 NMR) showed the successful preparation of various monomers as well as polymers. The thermal properties of two series were characterised by differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). We observed dramatic colour changes and Grand-jean textures of polymers using polarised optical macroscope (POM). The results of POM and selective reflection showed that both series of polymers are cholesteric liquid crystals. In the latter series, crosslinking by Diels-Alder reaction can make the liquid crystal better oriented, which can maintain their wonderful liquid crystal (LC) texture and selective reflection, and at the same time, it has a certain regulation effect on the appearance of cholesteric Grand-jean blue texture. The results of X-ray diffraction (XRD) further proved the two series of polymers are cholesteric liquid crystals.

Automated summary

This paper synthesizes a series of liquid crystal polymers (PF) by hydrosilylation method using monomers containing furan group (MA), cholesterol group (MB), D(+)-camphoric acid group (MC), and cyano-group (MD) catalyzed by platinum catalyst. Another series of liquid crystal polymers (EF) is synthesized by the Dies-Alder reaction with cross-linker containing bismaleimide group. The successful synthesis of monomers and polymers is confirmed by FT-IR and H-1 NMR analysis. The thermal properties of the polymers are characterized by DSC and TGA, and the liquid crystal behavior is observed using POM and XRD.