Design And Preparation Of Graphene-based Polymer Nonlinear Optical Functional Materials

Two-dimensional graphene discovered most recently has been at the center of a significant research effort due to its excellent electrical, optical,thermal and mechanical properties. However, the poor solubility in solvents seriously limits the exertion of its great potentials. Design and synthesis of graphene-based solution-processed organic/polymeric materials are the key issue for the development of graphene-based molecular optoelectronic and photonic devices. Polymers have virtues of processability, adjustable structure and so on. So that, the improvement of solubility and other properties of graphene can be realized by grafting polymers to graphene.The thesis is focused on the synthesis of graphene based polymer hybrid materials, and the preliminary studies on their structures and nonlinear optical(NLO) properties (including optical limiting performance).Chapter 1 reviews preparation and research progress of graphene and its derivatives.Chapter 2 reports the functionalization of thermally-reduced graphene oxide (RGO)with poly(N-vinyl-carbazole) (PVK).In Raman spectrum of RGO-PVK, covalent graftings of the PVK chains onto the surface of RGO led to the red-shifts of both the D- and G-bands, and the Id/IG ratio of RGO-PVK was increased. In addition, the resulting material demonstrated improved solubility simply due to PVK acting as a surfactant, and displayed excellent broadband optical limiting (OL) responses at 532 and 1064 nm because of the effective combination of the different NLO mechanisms.Chaper 3 describes two kinds of functional materials. The hybrid material GO-PANI was produced by covalently bonding graphene oxide and polyaniline(PANI) together using acylamidation reaction, while the nanocomposite (Ag/PANI) of PANI and Ag was prepared by doping Ag nano particles into PANI. In the IR spectrum of GO-PANI, the peaks of C=O and C-N stretching in amido bond appeared. TEM images of Ag/PANI indicated the distribution of the Ag nano particles in PANI. Open aperture Z-scan showed that GO and Ag both enhanced the optical limiting property of polyaniline. Moreover, the optical limiting of GO-PANI was better than that of Ag/PANI.In Chapter 4, graphene was covalently modified with thiophene and poly(3,4-ethylenedioxythiophene) (PEDOT). IR spectrum of the resulting material rGO-PEDOT proved the existence of C=O inα,β-α',β'-unsaturated ketone and C-O-C in 3,4-ethylenedioxythiophene. In Raman spectrum of rGO-PEDOT, the shifts of D and G bands illustrated the interaction among thiophene, PEDOT and rGO. The optical limiting response of rGO-PEDOT was observed when irradiated at 532 nm laser pluse.In the final chapter of this research work, poly[(1,4-diaminobenzene)-(3,6-N-octyl carbazole)](PACz) was synthesized, and then GO was functionalized covalently with this oligomer. The solubility of the resulting material GO-PACz was better than that of GO. In the spectrum of GO-PACz, the new peak appeared which was assigned to C=O stretching in amido bond. The characteristic peak of N in NH-C=O was observed from the Nls XPS spectrum of GO-PACz. Its nonlinear optical properties are being tested.