Polyacetylene as heterogeneous catalyst for electroless deposition of bulk amorphous metals
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Amorphous alloys have been produced by a variety of methods, the most common of which is rapid quenching of a melt. Other methods which have their own advantages are electroplating1 and electroless (autocatalytic) plating.2"6 These processes allow a continuous buildup of an alloy on a substrate.7 In the electroless method, the deposition reaction occurs only on a catalytic surface8'9 or in the presence of a deposit-promoting catalyst.10 It is evident that once deposition is initiated on a surface, the metal being deposited must, itself, be catalytic in order for deposition to continue. The thickness of the deposited amorphous layer, on conventional catalytic surfaces, does not exceed more than a few tens of micrometers.1012 Conductive polymers have been investigated as catalytic materials in recent years. The first investigation of electrocatalytic activity of a conducting polymer was performed by Nowak et al.13'14 They found that a crystalline surface of polymeric sulfur nitride, (SN)*, shows some electrocatalytic activity. Polyacetylene, (CH)*, which is the simplest conjugated polymer, consists of a complicated network of fibrils which have a diameter of several hundreds of angstroms and a length of several thousand angstroms. The fibrils, which are partially crystalline, consist of chains of CH groups arranged in a zigzag configuration. The fibrillar morphology makes the surface area very large, about 60 m2 g~V5 The polyacetylene (hereafter abbreviated PAc) surface is highly absorbing for oxidizing or reducing agents, i.e.,/?- or n-dopants. The electronic structure of PAc can be modified by doping. The intrinsically insulating PAc can through doping acquire metallic properties. Besides the vast amount of literature on PAc's physical properties, its chemical properties have also been studied. In this respect the J. Mater. Res., Vol. 5, No. 8, Aug 1990
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reversibility of the doping process has been the chief concern of investigations of PAc as an electrode for rechargeable batteries. PAc has also been investigated as a catalytic electrode in an aqueous electrolyte for the reduction of gaseous oxygen, hydrogen peroxide, or perchloric acid,16 and in a H 2 D 2 exchange reaction.17 P-doped PAc has been selected as a possible candidate for photocatalytic hydrogen generation.18 In this communication the synthesis and the wetting of a new foam-like PAc is described. The catalytic properties of PAc with different morphologies will be presented qualitatively by comparison with some catalytic metals and some other conducting polymers. In the last part the preparation of bulk amorphous alloys through autocatalytic plating on a PAc substrate is described and the properties of the resulting twocomponent system are briefly discussed. II. EXPERIMENTS AND RESULTS A. Film preparation
PAc films were synthesized by the Shirakawa technique,15 at -78 °C, with Ti(OBu)4-Al(Et)3 as catalyst. The mole ratio Al/Ti was 4. Toluene or pentane was used in repeated washing of the films. Th
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