Fluorescent cholesteric liquid crystal polymers containing different naphthalimide groups – preparation and performance

Fluorescent liquid crystal polymers (PFL1-PFL10) with temperature dependent of selective reflectance and fluorescence properties were obtained by graft copolymerisation of naphthalimide fluorescent monomers (FA and FB) containing different halogen atoms with cholesterol monomer (MA) and monomer containing cyanide (MB) onto polysiloxane chains. Among them, PFL2-PFL7 are polymers containing FA and FB fluorescent monomers, while PFL1 and PFL8-PFL10 are polymers containing only FA or FB fluorescent monomer; detailed comparative analysis was conducted on their liquid crystal and fluorescence performance. The structures of monomers and polymers were characterised using infrared spectroscopy and nuclear magnetic resonance, and the synthesised monomers and polymers conform to molecular design. By analysing the liquid crystal and thermal properties of the polymer through POM, DSC, XRD and TGA, it was demonstrated that the polymers are cholesteric liquid crystal polymer with excellent performance. The fluorescence properties of the polymer were analysed by fluorescence spectroscopy, and it was found that fluorescence quenching only occurs when the total content of FA and FB exceeds 20%. Simultaneously, the relationship between fluorescence performance and temperature was studied, and beneficial conclusions were drawn.