Synthesis Of Ionic Polyfluorene And Optical Properties Research

Ionic conjugated polymers are widely used in biomedicine,environmental monitoring and optoelectronic device development due to its excellent electronic conductivity and solubility;Ionic chiral polymers respond rapidly to light,electricity,pH,etc.,making them often used as chiral optical switches.On this study,the functional groups included the imine bond that can capture the metal ions,the conjugated structure with pyridine ring and the chiral central were introduced into the ionic polymer structure,preparing three novel ionic polymers by which the optical properties were investigaed.In the organic synthesis,FT-IR and ¹H NMR were used to characterize and analyze the products at all stage.Firstly,three diamine monomers were respectively subjected to the fluorene-containing bis-aldehyde monomer and byaldehyde amine condensation reaction to prepare the conjugated polymer P1 and chiral polymers P2 and P3;and then,Substitution reaction on theside chain of polymer to prerared ionic conjugated polymers IP1,chiral polymers IP2 and IP3.In the study of optical properties of polymers,the effects of different solvents,temperature and metal ions on their optical properties were investigated by UV-vis,fluorescence and CD spectroscopy.IP1 exhibited different UV-vis absorption and fluorescence emission spectra in different solvents as well as the different Stokes shift.The absorbance and fluorescence intensity of IP1 decreased with the increasing of pH.Compared with other metal ions on the effect on the fluorescence properties,it was found that the fluorescence quenching effect of Fe²⁺and Fe³⁺on IP1 was more effective and the fluorescence intensity was reduced to 70%.IP2 has the strongest UV absorbance at pH=7.The CD signal of polymer IP2 was weakened significantly by Sn²⁺,Fe²⁺,Fe³⁺,Cr³⁺,Cu²⁺,Ni²⁺,Co²⁺and Ag⁺,and the sensitivity decreased in turn.The reason may be that the metal ion and the imine functional group?-C=N-?in the main chain of the polymer can formed coordination bonds,which make the change of spatial distribution and arrangement state of the polymer chain,thus lead to the the chiral signal changed.Other metal ions such as Hg²⁺,Zn²⁺,Mg²⁺,Mn²⁺,Ca²⁺,Na⁺,Ba²⁺and K⁺made the CD signal of IP2 changed particularly weak.IP3 has the strongest UV absorbance at pH=6.The absorbance of IP3 in different solvents varies greatly,IP3 has the strongest absorbance in ether solvent and IP3 does not have CD signal in water.IP3 showed different circular dichroism in different solvents.The effects of metal ions on the CD signal of IP3 were investigated by circular dichroism spectroscopy.The results showed that Sn²⁺,Fe³⁺,Fe²⁺,Cr³⁺,Cu²⁺,Ni²⁺,Co²⁺and Ag⁺reduced the CD intensity of IP3 and its sensitivity decreased in turn.Other metal ions such as Hg²⁺,Zn²⁺made the CD signal of IP3 changed particularly weak.