Solvent dispersion process, conductive

Figure 4. Conductive core coating by solvent dispersion process...

TABLE V Calculation Of Energy Required For Conductive Core Coating, LPS Process vs Solvent Dispersion Process... 

Polypyrrole/poly(ethylene-co-vinyl acetate) conducting composites with improved mechanical properties were prepared by a similar method [167], In addition, polyaniline/polystyrene [168] and polyaniline/poly(alkyl methacrylate) [169] composites have been synthesised. A solution of persulphate in aqueous HC1 was added to an o/w HIPE of polymer and aniline in an organic solvent, dispersed in aqueous SDS solution, causing aniline polymerisation. Films were processed by hot- or cold-pressing. 

The solvent diffusion/spontaneous emulsification process can create much smaller droplet sizes than the solvent evaporation method. In this case, the dispersed phase is composed of a water-immiscible solvent and a water-miscible solvent, which is emulsified into an aqueous solution. The diffusion of the water-miscible solvent causes turbulence and further breakup of the droplets in the emulsion. The removal of solvent can be conducted similarly to the solvent evaporation method. 

Colloidal dispersions provide an alternative route for developing solvent-processible conducting polymers and can be produced chemically [129] or electrochemically [130] by the oxidation of monomer in the presence of a steric stabilizer. For electrochemically produced colloids, the steric stabilizer impedes polymer deposition on the electrode surface. Fine colloidal silica can also be used as a dispersant, and nanocomposite colloids of polypyrrole and polyaniline have been prepared using... 

Solid-phase sorbents are also used in a technique known as matrix solid-phase dispersion (MSPD). MSPD is a patented process first reported in 1989 for conducting the simultaneous disruption and extraction of solid and semi-solid samples. The technique is rapid and requires low volumes (ca. 10 mL) of solvents. One problem that has hindered further progress in pesticide residues analysis is the high ratio of sorbent to sample, typically 0.5-2 g of sorbent per 0.5 g of sample. This limits the sample size and creates problems with representative sub-sampling. It permits complete fractionation of the sample matrix components and also the ability to elute selectively a single compound or class of compounds from the same sample. Excellent reviews of the practical and theoretical aspects of MSPD " and applications in food analysis were presented by Barker.Torres et reported the use of MSPD for the... 

Microstructures of CLs vary depending on applicable solvenf, particle sizes of primary carbon powders, ionomer cluster size, temperafure, wetting properties of carbon materials, and composition of the CL ink. These factors determine the complex interactions between Pt/carbon particles, ionomer molecules, and solvent molecules, which control the catalyst layer formation process. The choice of a dispersion medium determines whefher fhe ionomer is to be found in solubilized, colloidal, or precipitated forms. This influences fhe microsfrucfure and fhe pore size disfribution of the CL. i It is vital to understand the conditions under which the ionomer is able to penetrate into primary pores inside agglomerates. Another challenge is to characterize the structure of the ionomer phase in the secondary void spaces between agglomerates and obtain the effective proton conductivity of the layer. 

The same kind of additives can also be used to make polymer films with high surface conductivity, greater than 10-3S, in a two-step process (Jeszka et al., 1999). The precursor organic compound, comprising neutral molecules, is first molecularly dispersed in the polymer film, which is then swelled with solvent vapour at the same time that it is exposed to either iodine or bromine. The CT salt then precipitates close to the surface of the polymer film, producing a localised conductive layer. 

---