Coating of uniform inorganic particles with polymers: III. Polypyrrole on different metal oxides

Abstract

Five kinds of uniform metal oxide particles (α-Fe2O3, CeO2, CuO, NiO, and SiO2) were coated with polypyrrole by reacting the dispersed solids with pyrrole in a water/ethanol medium without the use of a soluble oxidant. When the process was carried out in air, all particles were coated with the polymer, although the thickness of the layer varied on different cores. In CuO dispersions, independent polypyrrole particles were produced in addition to coated spheres. While oxygen is the major oxidant that initiates the polymerization of pyrrole, some metal oxides may also affect the reaction both in terms of the amount and the composition of the shell. Thus, α-Fe2O3 and SiO2 were found to be inactive in the polymerization, while CeCh and CuO react with the adsorbed pyrrole molecules through a reductive-dissolution process, in which the monomers are oxidized, causing a release of reduced metal ions.

Nanoengineering of Particle Surfaces

“…This approach was employed to obtain poly(pyrrole) coatings on a range of inorganic cores by using the active sites on the metal oxide surfaces to initiate the polymerization of pyrrole. [26,27] Hematite (a-Fe 2 O 3 ), silica-modified hematite, and cerium(IV) oxide (CeO 2 ) were coated with poly(pyrrole) by exposing the inorganic cores to the polymerization medium of pyrrole in an ethanol/water mixture and heating to 100 C. The poly(pyrrole)-coated a-Fe 2 O 3 and CeO 2 particles were found to be electrically conductive. [26] In a subsequent study, it was shown that CeO 2 and copper(II) oxide (CuO) react with the adsorbed pyrrole molecules through a reductive-dissolution process that involves oxidation of the monomers and release of the metal ions, whilst a-Fe 2 O 3 and silica (SiO 2 ) were found to be inactive in the polymerization.…”

“…[26] In a subsequent study, it was shown that CeO 2 and copper(II) oxide (CuO) react with the adsorbed pyrrole molecules through a reductive-dissolution process that involves oxidation of the monomers and release of the metal ions, whilst a-Fe 2 O 3 and silica (SiO 2 ) were found to be inactive in the polymerization. [27] Uniform poly(pyrrole) coatings surrounding the core can be obtained using this approach, as displayed in Figure 1 for poly(pyrrole)-coated SiO 2 particles. [27] It was further shown that the thickness of the polymer coating can be controlled by varying the contact time of the cores with the polymerization solution and that the polymer layer thickness is dependent on the type of core used and the presence of additional polymer (e.g., polyvinyl alcohol).…”

Designing of Nano Composites of Conducting Polymers for EMI Shielding

“…However, the higher energy of the quinoid section between them binds them together resulting in correlated motion. The net effect is the formation of a doubly charged defect acting like a single entity and delocalized over several rings (3)(4)(5) i.e., a bipolaron. The formation of bipolarons implies a net free energy gain in forming a closed shell defect from two open shell structures.…”

“…Depending on the nature of the components used and the method of preparation, significant differences in composite properties may be obtained. Nanocomposites of conducting polymers have been prepared by various methods such as colloidal dispersions [2], electrochemical encapsulation [3], coating of inorganic polymers, and insitu polymerization with nanoparticles [4] and have opened new avenues for material synthesis. The combination of the magnetic nanoparticles with conducting polymer leads to formation of ferromagnetic conducting polymer composite possessing unique combination of both electrical and magnetic properties.…”

Composition dependent magnetic properties of iron oxide-polyaniline nanoclusters

“…The agglomeration in these magnetic nanoparticles due to Vander Waal's and magneto static interparticle interaction hampers their use for technological applications. Several methods have been employed to reduce this problem of agglomeration, namely, blending colloidal nanomagnetic particles with polymers, coating of oxide particles with polymers like PVA, PVP,PMA etc., forming a core shell structure or embedding the particles in a polymer matrix [6][7][8][9]. These so called nanocomposites are also used in blend with conducting polymers like polypyrrole (PPY), polyaniline (PANI) etc.…”