Conducting polymers, ultrathin coatings

Figure 16.4 Electrochemical corrosion cell used for testing the ennobling effect of a conducting polymer. The mild steel sample (1) is coated by a thin epoxy layer and is in contact with a 0.1 M UCIO4 solution (aerated or deaerated) through a small hole. Polymethylthiophene (PMT) is deposited on a Pt electrode (2) a saturated calomel electrode (3) and a Pt counter-electrode (4) are used with either (1) or (2) as the working electrode. Electrodes (1) and (2) are galvanically connected and can be disconnected from the electrical circuit for specific measurements. (Reprinted with permission from Electrochimica Acta, Corrosion protection by ultrathin films of conducting polymers by U. Rammelt, P.T. Nguyen and W. Plieth, 48, 9, 1257-1262. Copyright (2003) Elsevier Ltd)...

Besides the electrochemical method, other methods such as the chemically initiated polymerization method, the vapor-phase methods, and the Langmuir-Blodgett method have been devised for the preparation of conducting polymers. In the chemical method, a chemical oxidant such as ferric chloride initiates the polymerization. Polymerization usually results in a powdery product and the resultant powder is then compressed into a pellet or dissolved in a suitable solvent such as methylene chloride or chloroform and spin coated on a substrate. In the vapor-phase technique, which is a variation of the chemical method, a monomer film is vacuum sublimed onto a glass substrate and then exposed to a solution or vapor of ferric chloride for oxidative polymerization. Films thus prepared are usually thick, of the order of micrometers. For some applications in which ultrathin and very uniform films are required, the Langmuir-Blodgelt technique for depositing monolayers has also been tried successfully [5]. 

Ultrathin Coatings Based on Conducting Polymers 14.3.5.1 How to Prepare Coatings That Work... 

Coating polymers with inorganic materials is now a well-established practice to achieve radical changes in surface properties (wettability, antistatit conduction, surface hardness) and hulk properties such as the gas-harrier property. RBS provides a convenient and usually accurate means to characterize the thickness of such films, especially when their lack of transparency makes optical characterization impossible. This is an important thickness range to he ahle to characterize accurately, as it typically spans the percolation threshold for ultrathin metallic coatings on polymers. ... 

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