Polymerous layers with acetylenic

FORMATION OF POLYMEROUS LAYERS WITH ACETYLENIC COMPOUNDS IN HYDROCHLORIC ACID ON METAL SURFACES... 

It has been demonstrated that surface basic sites of PCPs successfully catalyze polymerization in the nanochannels. Thus, the pillared-layer complex [Cu2(pzdc)2bpy] acted as a host for spontaneous polymerization of substituted acetylenes in a specific manner (Fig. 5) [67]. In the case of acidic monosubstituted acetylenes, the basic oxygen atoms from carboxylate ligands in [Cu2(pzdc)2bpy] produced reactive acetylide species that subsequently initiated anionic polymerization in the nanochannel. Compared with a control experiment using a discrete model catalyst... 

Metal-containing polymers can be synthesized by the vapor deposition polymerization of various monomer systems including organometallic compounds and metal-monomer co-condensates. Such co-condensates are produced by simultaneous or layer-by-layer deposition of metal and monomer vapors on substrate plates at low temperatures (usually, 77 K). Polymerization can proceed in different ways. Some metal-monomer systems polymerize during cocondensation (Ge and Sn with acetylene [11], Mg with CN-substituted p-xylylene [12]), most probably due to heat released at condensation. In references 13-16, co-condensates of metals (Pd, Ag, Au, etc.) and vinyl monomers... 

The electrochemical polymerization of pyrrole or thiophene readily lends itself to formation of composites. Polypyrrole-acetylene laminates have been made by using polyacetylene as an electrode 295). The polypyrrole forms as a 5 pm skin on the polyacetylene. If the polyacetylene is first doped, the polypyrrole completely permeates the film. In both cases the conductivity of the composite reached 30-40 S cm-1 and was much less sensitive than that of pure polyacetylene to exposure to moist air or water, so that the polypyrrole protects the polyacetylene even in the case where it permeates the film. In this latter case, treatment with ammonia caused the conductivity to drop by 30 x whereas for the sandwich films the conductivity dropped by 4600 x through the film but only 17 x in the surface layers. 

According to the literature /10,11/ plasma polymer layers contain free radicals which will react with oxygen and water in the atmosphere. In order to examine this fact plasmapolymerized acetylene was deposited using nitrogen instead of air. The elemental analysis of these films revealed less oxygen dian those deposited in air. This proves that most of the oxygen is incorporated into the layer during plasma polymerization. 

The liquid crystal polymerization method was modified to prepare a vertically aligned poly acetylene film [58]. As a result, a film with a very curious morphology was formed that was composed of two layers. The layer on the solvent side had a vertically oriented fibrillar structure, whereas the layer on the acetylene gas side had a randomly oriented one. The modified method is very promising for visualizing the polymer growth process and clearly demonstrates that PA chains grow in a liquid crystal solvent. 

The interpretation of the reaction mechanism is as follows. Acetylene molecules are located in face-centered sites in the ab plane of the unit cell. The molecular planes pile up along the c axis at a c/2 interval with the offset by b/2. The nearest molecules are located in four equivalent positions in the upper and lower layers. The polymerization probably proceeds through opening the triple bond with the subsequent formation of a single bond between adjacent molecules. Therefore the reaction is expected to be induced in the be plane rather than in the ab plane. 

The electrochemical polymerization method was used to prepare layers of conductive polymers on electrodes pre-coated with another conductive polymer or using films of a conductive polymer as electrode. This was the method used to prepare a composite of poly acetylene and polypyrrole [150,151] A sandwichlike composite with layers of polypyrrole adhered to polyacetylene was obtained using undoped polyacetylene electrodes. The use of doped polyacetylene induced pyrrole polymerization in the bulk of the film. A strong improvement in the stability of polyacetylene was observed exposure to ambient temperature of 30 days or to water for 20 minutes did not reduce the conductivity of both materials. 

Polymerization of extremely thin poly(acetylene) films (< 1 pm) on crystal surfaces by epitaxial growth (e.g., on frozen benzene) [40] also induced orientation in the deposited polymer layer. Substituted poly(pyrrole) films with a high anisotropy can be produced by the Langmuir-Blodgett technique [41 3]. 

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