Synthesis, Characterization, And Applications Of Nanocomposite Particles Of Polypyrrole

Recently, the preparation of conducting polymer-based nanocompositematerials has received intense attentions in the field of functional material.Conducting polymers are excellent functional materials, which havepotential applications in the field of antistatic coatings, anticorrosioncoatings, electromagnetic interference screen, microwave attenuation,electroics, photonics, sensors, biomaterials, energy storage materials, andcontrolled drug delivery system due to their variable conductivitiesranging from insulator to metallic, reversible redox reaction, andadjustable band gap. Conducting polymers are popular compositions inthe synthesis of nanocomposites. Polypyrrole (PPy) is one of the moststudied conducting polymers owing to their high conductivity, goodenvironment stability, excellent biocompatibility, and low cost. Greatefforts have been taken to prepare nanocomposites with extraordinaryproperties by designing the constituents and structures. In this thesis, a series of PPy-based nanocomposite particles were designed and preparedin gentle aqueous system, whose structure, morphology, formationprocess, and applications were explored. The main research works aresummarized as follows:1. Ag-PPy nanoparticles coated polymer composites were prepared byredox reaction of AgNO3and pyrrole in the presence of soap-free latexpoly(styrene-co-methacrylic acid)(P(St-co-MAA)). The product wascharacterized by TEM, SEM, FTIR, Raman spectroscopy, TGA,UV-vis-NIR, fluorescence spectroscopy, and four-point conductivitymeter. Raspberry-like Ag-PPy/P(St-co-MAA) nanocomposite particleswere obtained. The influences of reaction temperature, pH value of thesystem, and MAA concentration were investigated. It is found that theamount, distribution, and morphology of Ag-PPy nanocomposites can beadjusted by varying reaction temperature. The oxidative polymerizationrate of pyrrole by AgNO3increased as the pH value of the systemincrease from2.2to7.3. When the pH value of the system was about7and the reaction temperature was60oC, Ag-PPy nanocomposite candistribute relatively evenly on the surface of latex and form almostcontinous coating. In addition, the concentrations of MAA also havesignificant influences on the morphology of product. As the concentrationof MAA decreased from10wt%to0wt%, the Ag nanoparticlesdecorating evenly on the surface of latex became bulky aggregation and isolated in the system, whereas the rough PPy layer became uniform andsmooth. When soap-free P(St-co-SSNa) latex was used as template, onlyisolated Ag-PPy core-shell nanoparticles can be obtained. TheP(St-co-SSNa) latex particles acted as stabilizers instead of templates.The application of raspberry-like Ag-PPy/P(St-co-MAA) compositeparticles as catalysis and fluorescent quencher was explored.2. PPy-coated polymer nanocomposite particles were prepared usingsoap-free latex as template and metal cations as the oxidant. The productwas characterized by TEM, SEM, FTIR, TGA, and four-pointconductivity meter. It is found that PPy formed coating layer on thesurface of latex and hollow PPy spheres were obtained by solvent extractmethod. Soap-free latexes P(St-co-MAA) and P(St-co-SSNa) wererespectively used. The influences of the concentration of MAA and thereaction rate of oxidant were investigated. As MAA/St wt%decreasedfrom11.11to0, the morphology of PPy layer became homogeneous anddense. Bulky porous PPy material can be obtained as the concentration ofMAA is high, while PPy hollow spheres would be got as theconcentration of MAA is low. Both FeCl3·6H2O and CuCl2·2H2O wereused as the oxidant. Similar phenomena were obtained. However, whenthe concentration of MAA is high, the PPy coating layer obtained byusing CuCl2·2H2O as oxidant was not as rough as that of FeCl3·6H2O.The morphology of PPy/P(St-co-SSNa) was similar to that of PPy/P(St-co-MAA).3. PPy-PS hybrid hollow spheres were designed and prepared by afacile method. Common PS emulsion without any functional groups wasprepared by traditional emulsion polymerization. PPy-PS hybrid hollowspheres can be obtained when the oxidative polymerization of pyrrolewas carried out in the presence of PS latex. It is proposed that part of PSmigrated as the formed PPy deposited on the surface of PS latex. Thehollow voids can be handily adjusted by changing the diameter of PSlatex. The hollow structure was confirmed by TEM, SEM, andmicrotomed SEM. The formation of PPy-PS hollow spheres wasmonitored by TEM. It is found that hollow structures had formed afterreaction for about25min. The influences of the reaction conditions werealso investigated. As the amount of PPy decreased from58wt%to25wt%,the ratio of hollow spheres decreased sharply. The formation of hollowstructure was inhibited obvious when hydrophilic molecules, such as PVP,were introduced on the surface of PS latex. It is conjectured that theformation of PPy-PS hollow spheres is driven by the capillary forceamoung the PPy nanoparticles deposited densely on the surface of PS,which induced the migration of PS. In addition, the swell of PS bypyrrole monomer also facilitated the migration of PS.4. Novel Ag-PPy nanoplates were prepared by seed-mediated method.TEM, SEM, and Raman spectroscopy were used to characterize the product. The influences of the amount of seeds and the kind of stabilizerswere also explored. Plate-like products can be obtained when PVP, PVA,and PSSNa were used as stabilizers, while line-like product was obtainedwhen PAANa was used as stabilizer. PPy coating layer on the surface ofsilver nanoplate is inhomogeneous with Santa-hat-like morphology. TheUV-vis-NIR spectra of the product indicated that the optical properties ofAg nanoplates can be preserved. The applications of Ag-PPy nanoplatesas fluorescence quenching agent were explored. The size of Ag-PPynanoplates can be easily adjusted by the amount of Ag seeds.