Synthesis And Characterization Of Side-Chain [60]Fullerene Polyesters With High Refractive Indices

Side-chain fullerene polyesters with high refractive indices(n>1.80) were synthesized by condensation polymerization from a fullerene diol with different diacyl chlorides, with the synergic effect from fullerenes and high refractive index polyesters. The Finkelmann’s decoupling effect method, which is used to design side-chain liquid crystalline polymers, is applied here by introducing flexible long spacer groups between the pendent fullerenes and polymer backbone to minimize the fullerene’s influence on chain stiffness and increase the solubility of fullerene polyesters. According to the Lorentz-Lorenz equation, four aromatic diacyl chlorides, terephthaloyl chloride, 1,4-naphthalenedicarbonyl chloride, 2,5-dibromoterephthaloyl chloride and 2,5-thiophenedicarbonyl chloride, are chosen as monomers due to their high molar refractive index value, to obtain high refractive index polyesters with the coupling of fullerenes. The detailed contents are outlined as following:(1) Synthesis and characterization of fullerene diol monomer. The fullerene diol monomer with flexible long spacer groups was synthesized and characterized by 1H NMR, 13 C NMR and MALDI-TOF-MS, which confirms the chemical structure.(2) Syntheses and characterizations of side-chain fullerene polyesters. Using a model diol monomer, the optimum polymerization condition was investigated. Following this, four side-chain fullerene polyesters were obtained by the condensation polymerization of the fullerene diol monomer with four diacyl chlorides. The number-average molecular weights of these polyesters were obtained by a quantitive NMR technique using end-group analysis. The diffusion coefficients determined by 1H DOSY(diffusion-ordered NMR spectroscopy)furtherly verified the successful syntheses of fullerene polyesters. The polyesters were characterized by FTIR, TGA and UV-Vis spectroscopy, respectively.(3) The refractive indices of the fullerene polyesters were determined by spectroscopy ellipsometry(SE). The polymers all exhibit high refractive indices with the value higher than 1.80. Among them, the polyester with thiophene moiety has the highest refractive index(1.864 at 589 nm), one of the highest refractive index from intrinsic polymers that has been reported. The results show that high refractive indices can be achieved by the synergic effects from high-content fullerene and polyester backbone with high molar refraction values. The theoretical values calculated by Lorentz-Lorenz equation agree well with the experimental values determined by ellipsometry, and the absorption coefficient value derived from ellipsometry agrees well with that measured by spectrometer, indicating the data reliability.