Electrochemical Polymerization And Optical Properties Of Polymer Light-Emitting Materials

Emission color tuning of conjugated polymers by copolymerization has attracted great attention in recent years.Electro-copolymerization is one of the most valuable techniques for obtaining conjugated polymer films with controlled thickness.Furthermore,the obtained polymer films can be characterized by electrochemical and spectral methods easily.In this thesis, poly(1,4-diethoxybenzene-co-3,4-ethylenedioxythiophene)(poly(DEB-co -EDOT)),poly(1,4-diethoxybenzene-co-3-methylthiophene)(poly(DEB-co -MTh)),poly(pyrene-co-3,4-ethylenedioxythiophene)(poly(Py-co-EDOT)) and poly(pyrene-co-3-methylthiophene)(poly(Py-co-MTh)) are polymerized electrochemically in acetonitrile(ACN) containing tetrabutylammonium perchlorate(TBAP) by the direct oxidation of monomers mixtures.Both structure characterization and property investigation of corresponding pure polymers and copolymers are carried out systematically.The successive cyclic voltammetry(CV) curves of the monomer mixtures and FTIR spectra of the polymers indicate that the obtained substances are copolymers,not the blends of corresponding homopolymers. The electrochemical response of the copolymers prepared at various scan rates shows that the peak currents are proportional to the scanning rates, indicating reversible redox characteristic of the copolymer films.Moreover, after successive scan between oxidation and neutral state,the decreasing of redox peak current of the copolymer films is not obviously,implying that these copolymer films have good electrochemical stability.The morphology of copolymer films on Indium Tin Oxides(ITO) glass are investigated by scanning electron microscope(SEM).The SEM photographs of poly(DEB-co-EDOT) and poly(DEB-co-MTh) show that the copolymer films are more uniform and compact than PDEB film, implying that the film morphology can be improved by the incorporation of EDOT and MTh units into the polymer chains.While the morphologies of poly(Py-co-EDOT) and poly(Py-co-MTh) films are quite different from those of corresponding homopolymers.The optical properties of the copolymers are investigated by UV-vis absorption and photoluminescence(PL) measurement in detail.UV-vis absorption spectra of four copolymers show that the position of UV-vis absorption peaks red-shifts when EDOT and MTh concentrations in feed ratios increase.Besides,the position of UV-vis absorption peaks also red-shifts in certain extent when the polymerization potential increases.The red-shift of absorption peak for either poly(Py-co-EDOT) or poly (Py-co-MTh) is less obviously compared with that of the poly (DEB-co-EDOT) and poly(DEB-co-MTh).PL spectrum of Poly (DEB-co-MTh) indicates that the position of PL emission peaks red-shifts with increasing the feed ratio of EDOT/DEB,and poly(Py-co-EDOT) has boarder emission wavelength region between 400 nm and 550 nm than corresponding homopolymers.When EDOT and MTh concentrations increase in feed ratios,the position of PL emission peaks for either poly (Py-co-EDOT) or poly(Py-co-MTh) also presents red-shift,which is less obvious than those of poly(DEB-co-EDOT) and poly(DEB-co-MTh).