Polyvinyl alcohol conductivity

If polyvinyl alcohol is used as the reducing agent and the oxidation is conducted in the presence of vinyl monomer, grafting occurs. This method of grafting yields substantially pure graft copolymers since the free radicals are formed exclusively on the polymer backbone. 

Fig. 7. Solid state molecular transistor based on polyaniline bridged microelectrodes. PVA layer of polyvinyl alcohol 1 drain current Vg gate voltage rendering the polyaniline non-conductive Vg gate voltage switching on conductivity of the polyaniline layer (from ref.

With increasing pH the reaction became less complete as the reverse reaction + TiOj MV + Ti02 became more important. A potential of the conduction band of the TiOj particles of —0.1 to —0.2 V (pH = 0) was derived from these measurements. Stabilization of the particles by polyvinyl alcohol did not change this potential. Particles of 80 nm diameter had the same potential as particles of 7 nm. 

A colloidal suspension of conductive vanadium pentoxide [130] can be used to perform intercalation, adsorption or encapsulation of electroactive molecules or biomolecules for electrodes or biosensor realization [131]. Encapsulation of glucose oxidase in nanocomposite films made with polyvinyl alcohol and V205 sol-gel matrix or in ferrocene intercalated V2Os sol-gel [132] were envisaged to prepare glucose biosensors. 

Fig. 4.13 (a) Semilogarithmic plot of conductivity versus the nanotube content (wt%) in poly(phenylene vinylene-co-2,5-dioctoxy-m-phenylene vinylene) (PMPV) [2]. (b) Frequency dependent conductivity of carbon nanotubes at different wt% in PmPV (filled symbols) and polyvinyl alcohol (PVA) (unfilled symbols) based composites [250]. 

When heated, polyvinyl chloride (PVC) and polyvinyl alcohol (PVA) lose HC1 and H20, respectively, to produce dark-colored conductive polyacetylene. Superior polymers of acetylene can be made by the polymerization of acetylene with Ziegler-Natta catalysts. The conductivity of polyacetylene is increased by the addition of dopants, such as arsenic pentafluoride or sodium naphthenide. 

The photoelectrochemical reduction of the N = N double bond of the diaryl azo dye methyl orange can be similarly sensitized by colloidal titanium dioxide les, isoj The reaction was sensitive to pH and the identity of the organic redox reaction could be shifted by conducting the photoreaction in the presence of surfactants. Cationic surfactants increased the efficiency of oxidative cleavage by inhibiting charge recombination. Polyvinyl alcohol instead favored reduction. The ambident photoactivity of methyl orange thus makes it an attractive probe for activity of irradiated semiconductor suspensions. 

Percolation threshold pc corresponding transition to metal conductivity in composite films from Teflon with Au nanoparticles is 30 vol.% [36]. The similar transition to semiconductor conductivity in films of polyvinyl alcohol containing nanocrystals CuS takes place at pc 15-20 vol.% [88]. In cryochemically synthesized films PPX with Ag nanocrystals conductivity of metal type is achieved already in films with Ag content 7 vol.% conductivity of these composite films increases with the lowering temperature proportional to (1 — j.Ty1 similarly to that of block metals, but coefficient a is 2.5 times less than value x0, characteristic for block silver [86]. 

As a base of proton conducting membrane polyvinyl alcohol (PVS) and phenolsulfonic acid (PSA) was synthesized [9]. Membrane is rendered on a surface of a catalytic layer and dries up at room temperature. As shown in [9], at ratio PVS PSA=4 1 the membrane surpasses widely used in PEMFC membranes on the Nafion basis. Besides, experimental data testily that the solution can successfully be used as a connecting element for the anode and the cathode bonding at FC assembly. 

A composite material made of zinc oxide and polyvinyl alcohol was prepared by a sonochemical method [135]. Annealing of the composite under air removed the polymer, leaving porous spheres of ZnO. This change was accompanied by a change in the surface area from 2 to 34 m g k The porous ZnO particles were used as the electrode material for dye-sensitized solar cells (DSSCs). They were tested by forming a film of the doped porous ZnO on a conductive glass support. The performance of the solar cell is reported. 

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