Polyacetylene Transparent Films

Suspensions of polyacetylene were prepared as burrs or fibers (46) by using a vanadium catalyst. When the solvent was removed, films of polyacetylene were formed with densities greater than that prepared by the Shirakawa method. These suspensions were mixed with various fillers to yield composite materials. Coatings were prepared by similar techniques. Blends of polypyrrole, polyacetylene, and phthalocyanines with thermoplastics were prepared (47) by using the compounding techniques typically used to disperse colorants and stabilizers in conventional thermoplastics. Materials with useful antistatic properties were obtained with conductivities from 10" to 10" S/cm. The blends were transparent and had colors characteristic of the conducting polymer. For example, plaques containing frans-polyacetylene had the characteristic violet color exhibited by thin films of solid trans-polyacetylene. 

When PVAPAC films, optimized with respect to conjugation length distribution and PAC concentration, are stretched in a controlled manner they turn into highly dichroic transparent neutral grey POLPAC filters (Fig. 1.10). The absence of coloration is indicative of an exceptionally highly ordered PAC state in these novel all polymer broadband polarizers based on polyacetylene (POLPAC ). 

Polyacetylene is a colorful polymer. The cis isomer transmits red light, the trans isomer blue, and because these polymers often come in mixtures of cis and trans, various shades of purple result. If well formed films of polyacetylene are made, the surfaces reflect silver and, sometimes, gold. Polyacetylene in powder form appears black. The vacuum line experiments produced membranes which appeared purple when wet with solvent (transmitted light - the membrane is transparent when wet) and silver when dry (reflected light-the membrane is opaque when dry). 

Special techniques were applied to orient the (CH) in order to attain high conductivities (i.e. values greater than 100 000 S cm [19] and parallel fibrils. Similarly, it is possible to make transparent (CH) film with a conductivity of over 5000 S cm The polyacetylene is produced on a plastic film and stretched together with the supporting material, later it is complexed, e.g. with iodine, under standard conditions. 

Similarly, transparent (CH)x film can be made that has conductivity values greater than 5000 S/cm. The polyacetylene is produced on a... 

We have made extensive use of organic insulator layers in MIS devices. The interest here is, firstly, to establish the compatability of the polyacetylene with the insulator as shown in section 6, we find that the polyacetylene layer is better ordered when formed on an organic layer than when fcamed on silicon dioxide. Secondly, we were keen to be able to fabricate structures which are optically transparent over die whole region of interest for polyacetylene (up to 2.5 eV) those fabricated on silicon substrates are limited by the silicon band gap (1.1 eV). We have used principally polyimide and PMMA, though the maximum values of EfFb are considerably lower than obtained with silicon dioxide. Polyimide has the advantage that, after spin-coating from solution, the film is heat-treated to render it insoluble, and it is not.affect d by further treatment with solvents such as those used for the Durham precursor. In contrast, PMMA remains soluble after deposition, and devices were fabricated with PPMA applied on top of the previously-converted polyacetylene film. 

We have carried out an investigation of the electrical and electro-optical properties of a series of Schottky barrier diodes fabricated with polyacetylene sandwiched between two metal contact layers, one to form the Schottky barrier and the other (gold) to provide an ohmic contact [56]. This type of structure is straightforward to fabricate with an extrinsically-doped semiconductor and there have been several reports of such devices which use polyacetylene or other conjugated polymers [57-62]. The details of the device fabrication have been given in section 3.2, and we show in figure 10 the details of the typical structures that we have used for this work. We have worked with relatively thick films of polyacetylene, in the range 500 - 1(XX) nm, so as to avoid the possibility of short-circuits tetween top and bottom electrode, but we have kept the metal contact layers thin so that they are semi-transparent and allow optical transmission measurements. 

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