Study On The Preparation And Properties Of Polymers Containing Triphenylamine Units And Their Composite Materials

Electrochromism(EC)can be defined as a reversible and visible change in the transmittance and/or reflectance of a material by applying different voltages or electric currents with the result of electrochemical oxidation or reduction.Electrochromic materials(ECMs)exhibit a reversible optical change in absorption or transmittance upon being electrochemically oxidized of reduced,which have extensive been applied as intelligent materials,such as smart windows,displays and electrochromic devices.Graphene(RGO)has been the most promising candidate of conducting materials since its discovery,owing to the many advantages such as large specific surface area,great electrical conductivity and so on.In recent years,there has been great interest in using graphene-based nanofillers,such as graphite nanoplates(GNPs),graphene sheets(GS),and graphene oxide(GO),to fabricate a new class of advanced polymer composites with unique mechanical and thermal properties.Most of them are focused on grafting styrene,aniline,and 3,4-ethylenedioxythiophene(EDOT)onto RGO.In this article,we have synthesized several electrochromic polymers and composites.These materials exhibited enhanced properties and NIR electrochromic characteristics with promising applications.In the first chapter,we introduce the tendency and theoretical basis of EC.In the second chapter,we developed a series of RPSBs based on N,N'-bis(4-aminophenyl)-N,N'-bis(?-naphthyl)-bisphenylenediamine by reducing conjugated Poly Schiff Bases(PSB).The RPSBs exhibit excellent solubility in many polar organic solvents and inherite good electrochromic characteristics and display high sensitivity and specificity on the detection of trifluoroacetic acid(TFA)and HCl(10-13 mol/L).The aromatic RPSBs exhibit photoluminescence(PL)emission maxima bands around 519-524 nm(about in the green region)in THF solution with PL quantum yields being from 0.363 to 3.638%.The highest occupied molecular orbital(HOMO)and the lowest unoccupied molecular orbital(LUMO)energy levels of these polymers are calculated to be at in the range from-4.789 to-5.153 and-2.238 to-2.796 eV.Most of them exhibit transparent in original state,and show color in oxidized state upon increasing voltage,which are promising materials in display and chemical sensor fields.In the third chapter,we fabricated the ID nanobars by a simple and feasible method.From the scanning electron microscope(SEM)image,it is observed that the uniform width and depth ranging from several nanometers to micrometers within the pre-formed pores of hard-templates offers an efficient way to control over the size,shape and orientation of the polymer products.The ID nanobars PSB arrays exhibited excellent electrochromic characteristics and photoelectric property,which are promising materials for display devices and photoelectric conversion material for optoelectronic applications.In the forth chapter,we developed a method of preparing composite of RGO/PSB.First,GO was prepared by the oxidation of natural graphite powder according to a modified Hummers' method;Then reduction of exfoliated GO was carried out with hydrazine hydrate;Finally,PSB was directly used to react with RGO in the presence of an excess of N-methylglycine to produce a highly soluble RGO covalently functionalized with PSB.The structure and properties of the composites were investigated by Infrared Spectroscopy(IR),Raman spectrometry,SEM,Thermogravimetric analysis(TGA),PL,UV-VIS absorption spectra(UV)and Cyclic voltammetry(CV),and especially the chemical sensor for tetrahydrofuran(TNT),optic-electronic,electrochromic and acidochromic properties were studied.The result demonstrated that the resulting composite had the potential value in chemical sensor or optic-electronic field.In the fifth chapter,we demonstrate an effective approach for the fabrication of a series of polyamides(PA)-based composites with GO which were prepared by using in-situ polymerization,and the two parts were connected with chemical bonds.We hope that the strong ?-? interactions between GO and conjugated PA can lead to synergistic effects in improving performances of any parts,and the GO can act as dopants to interact with both N-H groups and quinoid units on the PA backbone,which can increase 'the degree of electron delocalization and hence can enhance electrical conductivity of the material.We also anticipate that the prepared composites have stable property of electrochromic switch with improved optical response times,and enhanced coloration efficiency with high NIR contrast.For comparison,electrochemical and electrochromic properties of the present composites and pure PA were both investigated.In the sixth chapter,we demonstrated an effective approach for the fabrication of a series of polyimides(PI)-based composites with GO by using poly(amic acid)s(PAA)/GO composites as the precursors,because the possible covalent interactions between functional groups of the GO and the PAA could suppress GO aggregation during the thermal imidization process.The prepared PI/GO films exhibit a remarkable enhancement of mechanical,thermal,electrical and electrochromic properties,indicating uniform dispersion of the GO sheets in the PI matrix.The properties prove that the polymers and composites in this paper are multipurpose materials which will be subject of hole-transporting,electrochromic,chemical sensor application in near future.