PROCESS FOR PRODUCING A POLYACETYLENE OR POLYDIACETYLENE FILM

Abstract: The present invention relates to an electric material, and particularly it relates to an organic substance having a polyacetylene linkage which exhibits electrical conductivity and nonlinear optical effect. More particularly, the present invention provides a process for producing an organic substance having a polyacetylene linkage which can be utilized, for example, as an electric material, said process com­ prising immersing a substrate having a hydrophilic surface in a solution of a substance containing an acetylene (-C≡C-) group and a chlorosilane (-SiCl₃) group dissolved in a nonaqueous organic solvent, thereby subjecting the substance containing an acetylene group and a chlorosilane group to chemical adsorption on the surface of the substrate, subjecting said substance to polymerization reaction by the use of radiation such as X-rays, electron beams, γ-rays, or the like, and thereby producing a polyacetylene.

Description: Polymers of acetylene derivatives have been extensively studied as optical and electronic functional materials because they have electrical conductivity and nonlinear optical effect by virtue of the primary main chain having a π-electron conjugated system which is contained in the molecule of each polymer. As a method for producing a polyacetylene, there is well known the polymerization method of Shirakawa et al. using a Ziegler-Natta catalyst. On the other hand, it is well known that employment of an amphipatic acetylene derivative having both hydrophobic group and hydrophilic group permits formation of a monomolecular film on water surface and formation of a built-up film by the Langmuir-Blodgett (LB) technique. The LB technique is a method which in recent years, has been considered hopeful as one constructing means in development of molecular devices in which molecules themselves have functions. When the LB technique is employed, a monomolecular film of an acetylene derivative of several Ångström order can be formed and a built-up film thereof can easily be obtained. However, polyacetylene derivatives now known are unstable to heat, pressure, ultraviolet rays, etc. in an atmosphere containing oxygen, and therefore study of their stabilization is in progress. But, until now no method for stabilizing an acetylene derivative polymer has been found. From EP 0 178 606 is known a process for producing a polyacetylene film on a substrate, comprising immersing the substrate having a hydrophilic OH-groups containing surface in a solution of a straight-chain hydrocarbon compound having a chlorosilane group on one end of the hydrocarbon chain and one or more groups being reactive to energy beams (e.g. acetylene or diacetylene) at an optional position in the hydrocarbon chain, in a nonaqueous organic solvent, and thereby subjecting the chlorosilane group of the compound and the OH-group on the surface of the substrate to a chemical reaction, whereby a monomolecular film of the reacted compound is formed in the substrate, and polymerizing the molecules of the compound by irradiation with energy beams. Production of a polyacetylene by the use of the above-mentioned monomolecular film producing process, in some cases, causes a structural distortion and hence becomes difficult. In detail, in order for a straight-chain hydrocarbon molecules to have a function therein, its reactive group is irradiated with some energy beams to be subjected to chemical reaction, but the terminal chlorosilane group of straight-chain hydrocarbon molecule constituting the monomolecular film contains an oxygen atom owing to the linkage -Si-O-Si-, and functional groups (acetylene groups) are too apart from each other to react with each other. Therefore, the reacting is insufficient. Moreover, even if the functional groups react to be bonded to each other, there is a large difference between the bond distance of the -Si-O-Si- at the end of straight-chain hydrocarbon molecule constituting the monomolecular film and the bond distance between the functional groups, so that a structural distortion is caused. It is the object of the present invention to provide a process for producing a polyacetylene or polydiacetylene film on a substrate which is stable even in an atmosphere containing oxygen. According to the present invention, there is provided a process for producing a polyacetylene or a polydiacetylene film comprising immersing a substrate having a hydrophilic surface in a solution of a straight-chain hydrocarbon compound having a chlorosilane group on one end of the hydrocarbon chain and one or more groups being reactive to energy beams at an optional position in the hydrocarbon chain, in a nonaqueous organic solvent, and thereby subjecting the chlorosilane group of the compound to chemical adsorption on the surface of the substrate, whereby a monomolecular film of the compound is formed on the substrate, and polymerizing the molecules of the compound by irradiation with energy beams, wherein said straight-chain hydrocarbon molecule forming a main chain has one or more side chains, and said group(s) reactive to energy beams are present in the main chain and in one or more side chains of said main chain. According to the process of the present invention, a monomolecular film is formed by using straight-chain hydrocarbon molecules having one or more side chains in optional positions of the molecules and reactive groups to impart a function in the main chain and the side chain, and then subjected to polymerization by irradiating the reactive groups with energy beams, and if necessary, the films subjected to polymerization are formed into a multilayer film, whereby there is solved the conventional problem that since the end of a straight-chain hydrocarbon molecular chain contains oxygen as shown by -Si-O-Si- and the straight-chain hydrocarbon molecule has no side chain, functional groups of the molecule are too apart to react with each other. Thus, the distance between the functional groups is reduced, so that their reactivity can be enhanced, and moreover occurrence or a structural distortion is reduced. By virtue of the characteristics described above, conditions under which radiation polymerization reaction or an acetylene derivative monomer lasts without a break, can be maintained by irradiating molecules of the acetylene derivative aligned in monomolecular state, so that it becomes possible to produce a straight-chain, ultra-high-molecular-weight polyacetylene having a continuous conjugated system. Furthermore, since the polyacetylene produced has an ideal structure, the production process of this invention is very effective. Now, examples of the present invention shall be described with reference to the Figures, wherein: Figs. 1(a) to (d) are cross-sectional views for explaining a process for producing a polyacetylene which is the first example of the present invention. Figs. 2(a) and (b) are cross-sectional view for explaining a process for producing a polydiacetylene which is the second example of the present invention. As the first example, a process for producing a polyacetylene is explained below, stepwise with reference to Fig. 1. Numeral 11 shows an optional substrate (e.g., a Si substrate) for forming a polyacetylene. Numeral 12 shows a hydrophilic film (e.g., a SiO₂ film) formed on the optional substrate 1. Numeral 13 shows a silane surfactant of the formula: (wherein each of p, g, r, s and t is an optional integer), said silane surfactant constituting a monomolecular film 16 comprising straight-chain hydrocarbon molecules which have a side chain at the (r+1)th carbon atom from the Si atom, an acetylene group (-C≡C-) 14 as functional group at the (q+1)th carbon atoms of the main chain from said (r+1)th carbon atom, an acetylene group 14' at the (t+1)th carbon atom of the side chain from said (r+1)th carbon atom, and a vinyl group at the end of the main chain. In the straight-chain hydrocarbon molecule before formation of the monomolecular film, the terminal group on the Si side in the above chemical formula is a chlorosilane group (-SiCl₃). The linkage is formed on the surface of the hydrophilic film (e.g., SiO₂ film) 12 by a monomolecular film forming method such as chemical adsorption method or Langmuir-Blodgett technique, whereby the monomolecular film 16 is formed. In this case, the straight-chain hydrocarbon molecules are formed into the film in a state in which the vinyl group (CH₂=CH-) 15 at the end of the molecule and the methyl group (CH₃-) 17 of the side chain are aligned on the surface of substrate (Fig. 1(a)). In order to make the monomolecular film 16 functional, the film is irradiated with far ultraviolet rays to carry out the photoreaction of the acetylene groups in the main chain and the side chain with each other, whereby a polyacetylene {-(-CH=CH) m -} 18 having a conjugated system is produced. This polyacetylene has electrical conductivity and nonlinear optical effect, can be utilized as a photoelectronic functional material, and can be shaped in an optional direction on the same plane. In this case, since the density of acetylene groups is twice as high as before, the photoreactivity of the acetylene groups with each other for forming a polyacetylene is high, and since both the main chain and the side chain form a polyacetylene, the problem of structural distortion is solved (Fig. 1(b)). In order to further form polyacetylene on the monomolecular film 16, the film is irradiated in a water vapor atmosphere with energy beams, for example, electron beams converged to the molecular diameter order to activate the aforesaid vinyl group, whereby a hydroxyl group 20 is added thereto (Fig. 1(c)). Subsequently, the same silane surfactant as the aforesaid surfactant 13, i.e., (wherein each of p, q, r, s and t is an optional integer) is added to the active group portion having a hydroxyl group added thereto, in the same manner as described above to form the linkage In the thus formed film, vinyl groups 21 are aligned on the surface of the added molecule, a higher-order multilayer molecular structure is formed, namely, polyacetylene can be formed (Fig. 1(b)). Although in the first example of the present invention, there is used the silane surfactant having one side chain of the formula: (wherein each p, q, r, s and t is an optional integer), the number of side chains may be increased if necessary. Although far ultraviolet rays are used as energy beams in the first example of the present invention, radiation such as X-rays, electron beams, etc. may be used for the polymerization. Although the terminal group of the side chain is a methyl group in the first example of the present invention, it may be replaced by a vinyl group. Although a diacetylene group is shown as a functional group in the first example of the present invention, other functional groups such as pyrrole group, thienylene group, phenylene group, etc. may, of course, be employed. Although an example of process for producing a polyacetylene is shown above, a polydiacetylene can easily be produced by a similar process. As the second example, a process for producing a polydiacetylene is explained below stepwise with reference to Fig. 2. Numeral 100 shows an optional substrate (e.g., a Si substrate) for producing a polydiacetylene. Numeral 101 shows a hydrophilic film (e.g., a SiO₂ film) formed on the optional substrate 100. Numeral 102 shows a silane surfactant of the formula: (wherein each of p, q, r, s and t is an optional integer), said surfactant constituting a monomolecular film 105 comprising straight-chain hydrocarbon molecules which have a side chain at the (r+1)th carbon atom from the Si atom, a diacetylene group (-C≡C-C≡C-) 103 as functional group at the (q+1)th carbon atom of the main chain from said (r+1)th carbon atom, a diacetylene group 103' at the (t+1)th carbon atom of the side chain from said (r+1)th carbon atom, and a vinyl group 104 at the end of the main chain. In the straight-chain hydrocarbon molecules before formation of the monomolecular film, the terminal group on the Si side in the above chemical formula is a chlorosilane group (-SiCl₃). The linkage formed on the surface of the hydrophilic film (e.g., SiO₂ film) 101 by a monomolecular film forming method such as chemical adsorption method or Langmuir-Blodgett technique, whereby the monomolecular film 105 is formed. In this case, the straight-chain hydrocarbon molecules are formed into the film in a state in which the vinyl group (CH₂=CH-) 104 at the end of the molecule and the methyl group (CH₃-) 106 of the side chain are aligned on the surface of substrate (Fig. 2 (a)). In order to make the monomolecular film 105 functional, the film is irradiated with far ultraviolet rays to carry out the photoreaction of the acetylene groups in the main chain and the side chain with each other, whereby a polydiacetylene {-(-CH=CH-C≡C-) m -} 107 having a conjugated system is produced. This polydiacetylene has electrical conductivity, is expected to be utilized as a molecular wiring, and can be shaped in an optional direction on the same plane. In this case, since the density of diacetylene groups is twice as high as before, the photoreactivity of the diacetylene groups with each other for forming a polydiacetylene is high, and since both the main chain and the side chain form a polydiacetylene, the problem of structural distortion in a molecular structure constituting a polydiacetylene is solved. A polyacetylene can be produced also according to the second example. In this case, the difference between processes for production of a polydiacetylene and a polyacetylene is due to the density of diacetylene groups in the main chain and the side chain of a straight-chain hydrocarbon molecule and the uprightness of the straight-chain hydrocarbon molecules. That is, when the density of diacetylene groups is high and the straight-chain hydrocarbon molecules are upright, a polyacetylene is formed, and when the molecules are in a relatively inclined state, a polydiacetylene is formed (Fig. 2(b)). When further formation of polydiacetylene on the monomolecular film 105 is desired, a multilayer structure of polydiacetylene can be formed by the same manner as described in the first example. In addition, it is obvious that in forming the multilayer structure, a functional portion such as polyacetylene, polydiacetylene or the like may be combined with each layer.

Claims: A process for producing a polyacetylene or a polydiacetylene film, comprising immersing a substrate having a hydrophilic surface in a solution of a straight-chain hydrocarbon compound having a chlorosilane group on one end of the hydrocarbon chain and one or more groups being reactive to energy beams at an optional position in the hydrocarbon chain, in a nonaqueous organic solvent, and thereby subjecting the chlorosilane group of the compound to chemical adsorption on the surface of the substrate, whereby a monomolecular film of the compound is formed on the substrate, and polymerizing the molecules of the compound by irradiation with energy beams, characterized in that said straight-chain hydrocarbon molecule forming a main chain has one or more side chains, and said group(s) reactive to energy beams are present in the main chain and in one or more side chains of said main chain. A process for producing a polyacetylene film according to claim 1, wherein said reactive group(s) is an acetylene group or a diacetylene group. A process for producing a polyacetylene film according to claim 1 or 2, wherein said energy beams are ultraviolet rays, far ultraviolet rays, electron ion beams, X-rays or γ-rays. A process for producing a polyacetylene film according to one of claims 1 to 3, wherein the number of carbon atoms constituting said straight-chain hydrocarbon molecule is 10 or more. A process for producing a polyacetylene film according to one of claims 1 to 4, wherein the end group other than the chlorosilane end group of said straight-chain hydrocarbon molecule is an unsaturated group. A process for producing a polyacetylene film according to claim 5, wherein a multilayer film is formed using the straight-chain hydrocarbon molecules having the unsaturated group. A process for producing a polyacetylene film according to claim 6, wherein said unsaturated group is a vinyl group.

Inventors: MINO, NORIHISA, OGAWA, KAZUFUMI, TAMURA, HIDEHARU
Applicants: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1988
Main classification: G02F1
IPC codes: B05D1, H01L21, C08F138, H01L51, G02F1