Design And Study Of Hyperbranched Conjugated Polymers Based On Imine Bond

Conjugated polymers have received considerable attention in both academic research and industrial applications because of their fantastic photoelectric properties. A variety of conjugated polymers with different light-emitting wavelengths and structures are being developed. Due to the simple preparation process together with the unique highly branched and globular structure which helps to suppress the aggregation and excimer, hyperbranched structure has been introduced into the conjugated polymers.In the present work, a new kind of hyperbranched conjugated polymers based on imine bond, which is also known as polyazomethine, has been designed and synthesized. Furthermore, two aspects including optical properties and functionalities of this kind of polymers have been studied. The dissertation is consisted of two parts as follows:(1) A kind of hyperbranched conjugated polyazomethine has been successfully prepared by the polycondensation of 3, 3'-diaminobenzidine with terephthalaldehyde. Because of the highly branched architecture, the terminal amino groups and the imine linkages in the backbone can easily form intra- or inter-molecular interactions, which affect the optical properties greatly. Based on this point, a simple approach to tune optical properties of the hyperbranched conjugated polymers has been developed via only adjusting the terminal-backbone interactions. Not only varying monomers feeding ratio to change the species and quantity of end-groups of hyperbranched polymer, but also adding some dopants, such as adopting acid to protonate the terminal amino groups and imine bonds in the main chain, adopting metal ions to coordinate the nitrogen atom of imine bonds, or adopting cyclodextrin to encapsulate the terminal groups which act as an insulating layer, can alter the terminal-backbone interactions. Correspondingly, the optical properties of hyperbranched conjugated polymers have been controlled.(2) The hyperbranched conjugated polyazomethine (HPPAM) has been used as a nanoreactor to prepare CdS quantum dots with small size and good dispersion. Since the nitrogen atom in the imine bond contains lone-pair electron, it can coordinate Cd2+ stably in the hyperbranched cavity. After adding S2-, the CdS can be synthesized in-situ. The CdS/HPPAM nanocomposites have been confirmed by Transmission Electron Microscope (TEM), Dynamic Light Scattering (DLS), Fourier Transform Infrared Spectroscopy (FTIR), Fluorescence (FL) tests. Furthermore, the effect of aging time on the fluorescence intensity of CdS/HP-PAM nanocomposites has also been studied. The results show that due to the encapsulation of hyperbranched polymer, the fluorescence intensity is almost unchanged, indicating no fluorescence quenching with the aging time increasing.