The synthesis of conjugated polymers with different length side chains and the effect on their nanoparticles

In recent years, conjugated polymers (CPs) and their nanoparticles (CPNs) were widely concerned and applied in many fields due to their outstanding advantages such as higher absorption coefficients, good photostability, low toxicity and good biocompatibility. However, most reports were focused on their applications, and rare attentions were given on the synthesis of CPs and the effect factors of CPNs’ morphology and properties. In this work, four CPs (P1, P2, P3, P4) with different length side chains were synthetized by Wittig–Horner reaction and further used to prepare CPNs by the nano-precipitation method. The CPs and CPNs were characterized and analyzed by Hydrogen Nuclear Magnetic Resonance (1H NMR), gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and transmission electron microscope (TEM). The absorbance and fluorescence emission spectra of CPs in tetrahydrofuran (THF) and CPNs solutions with different length side chains were investigated, and their quantum yields (Фs) were calculated by the reference method. The results showed that the synthetic CPs have narrow polydispersity index. Some interesting phenomenon appeared with the increased side chain length. The molecular weights will reduce except P3, and the absorbance and fluorescence emission spectra of CPs and CPNs are red-shifted. Фs are better and enlarged for CPs and CPNs, and better dispersion and uniform size were founded with longer side chains.