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ABSTRACT:Polypyrrole (PPy) films generated electrochemically from aqueous solutions have been found to have also good electrical conductivity. PPy films with the counter anions TsO-, so;, and NO; showed compact structure with apparent densities close to their flotation densities. The oxidative stability of PPy films has been compared by the value of the oxidation peak Epa around l.OV (vs. SCE) in the cyclovoltammogram. Prolonged electrolysis at +0.8V led to oxidative degradation. The temperature dependence of the conductivity followed the variable range hopping equation. However voltage shorted compaction (VSC) conductivity measurements might show pronounced differences at low temperatures for some of these films. No significant frequency dependence of the conductivity was found up to 35 GHz. In the IR spectra of electrochemically reduced PPy film by transmission the v (N-H) and sp 2 v (C-H) absorption bands were observed with no sp 3 v (C-H) bands. On grinding the reduced film with KBr to make powder compact the sp 3 v (C-H) absorption bands appeared indicating a mobile proton on theN-atom of the pyrrole ring. Definite evidence from IR spectra for the de-intercalation of the counter anion of the conducting PPy film during electrochemical reduction and chemical compensation has been obtained. 2 Recently it was found that pyrrole could be electrochemically polymerized and intercalated in aqueous solution with various types of counter anions to give PPy films of good conductivity, including detergent anions as n-alkyl sulfates, sulfonates, 3 alkyl aryl sulfonates, 4 tosylate anion, 4 and polymeric anions as polyvinyl sulfate and polystyrene sulfonate, 5 polymethacrylate, and sulfonated polyvinyl alcohol 6 as the counter anion. In our laboratory we found that with SO;', N03, and TsO-as the counter anions we can get compact conducting PPy films containing less than 20% void volume, other counter anions gave films of 70-85% void. 7 • 8 In this paper results of our recent investigation 9 on these dense conducting PPy films are summarized including morphology, oxidative stability, metallic conduction, chain structure, deintercalation and re-intercalation of the counter anions. A brief account for the molecular composites containing PPy is also given. MORPHOLOGY AND DENSITYConducting PPy films with Cl04, BF4, and PF6 as the counter anion show a morphology of hollow bowls of 20-30 11m diameter and consequently have very low apparent density 157

Diffuse reflectance infrared spectroscopy has been used to monitor the changes in functional groups on the surface of two woods (western redcedar and southern pine) when they are subjected to a range of artificial weathering conditions. The effects of light only, water only, and light plus water have been studied for a variety of exposure times. The changes in the chemical composition of the wood caused by light plus water is considerably greater than that caused by light only, whereas water alone causes no permanent chemical changes. The effects of some of these weathering conditions have been investigated for wood protected by varnish, for earlywood and latewood and for tangentially, radially, and cross-sectionally cut wood samples. The application of two coats of varnish was found to considerably reduce the weathering effects caused by UV radiation; earlywood undergoes light-only degradation faster than late wood; and the effect of weathering was found to be greatest for cross-sectional cut samples and least for radially cut samples. The weathering profile with depth of penetration has been studied in some detail for western redcedar, and our results show that, after 300 h of continual artificial weathering, the chemical changes are confined to the first 200 μm.

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