CN1254728A

CN1254728A - Adoping, induction and deposition process for preparing self-assembly superfilm of polyphenylamine

Info

Publication number: CN1254728A
Application number: CN 98121862
Authority: CN
Inventors: 蒋亚东; 李丹
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 1998-11-23
Filing date: 1998-11-23
Publication date: 2000-05-31

Abstract

A process for preparing superthin film of polyaniline, which can be used for chemical sensors, electrochromic device, luminous device, chemical modifying electrode and polymer FETs, uses intrinsic polyaniline solution and polymer acid as raw materials, which take part in doping reaction to prepare said film. In its preparing, the film thickness can be controlled in nm size by controlling the concentration of polyaniline solution and the times of assembly. The resultant film has the advantages of high adhesion to substrate, long service life, and stable electric and optical properties.

Description

The preparation method of doping induction and deposition polyaniline self-assembling ultrathin film

The invention belongs to the ultrathin membrane preparing technical field.

As everyone knows, polyaniline is the conductive polymers that a class is hopeful to obtain practicability most, have a series of special electricity and optical characteristics, in person in electronics, its film can be used widely at aspects such as luminescent device, transmitter, electrochromic device, chemically modified electrode and other molecular electronic devices.In some applications, as making transparent polymeric electrode, the sensitive membrane of chemical sensor is constructed complicated molecular electronic device structure etc., requires the thickness of film enough to approach, and thickness will be evenly, and film and substrate have stronger sticking power.Adopt the thickness of very difficult controlling diaphragms such as common casting method, spin-coating method or dipping polymerization to reach nano level, the poor adhesive force of film same substrate, film easily comes off from substrate.

In recent years, a kind of new thought for preparing ultrathin membrane has been proposed in the world, promptly so-called self-assembling technique.This technology is subjected to extensive attention both domestic and external in recent years because of its composition of controlling diaphragm and structure on molecular level easily.Especially after Germany scientist Decher proposed to utilize the static building block principle to prepare the method for multilayer film, this technology was generalized to rapidly in the preparation of the self-assembled film with various functional performances of polyelectrolyte, biologically functional molecule, conductive polymers, luminescent material, Nano semiconductor ion and soccerballene etc.Its basic skills and principle are that substrate is alternately immersed in the solution of polycation and polyanion, by the electrostatic attraction effect of polycation and polyanion, thereby alternately adsorb the molecular film of polyanion and polycation at substrate surface.The molecular chain of doped polyaniline is positively charged, according to static and hydrogen bond self-assembly principle, it is raw material that professor Rubner of Massachusetts Institute Technology waits with small molecules adulterated the polyaniline aqueous solution and organic polyanion, obtain a series of polyaniline self-assembled film (seeing document Macromolecules, 1997 30 volume the 9th phase 2712-2725 pages or leaves) and applied for patent (United States Patent (USP): Thin-filmheterostructure formed by molecular self-assembly of electrically conductive polymers; US5,536,573; Authorize day: on July 16th, 1996).Adopt this technology can be at the nanoscale thickness of controlling diaphragm easily, film that makes and substrate have stronger sticking power.But the weak point of this method is polyaniline and is easy to precipitation that in acidic solution polyaniline solutions uses and just can not continue after about 1 hour to use, and not only causes waste of material, and easily causes the film that makes inhomogeneous.In addition, owing to also have small molecules acid in the film that makes, easily volatilization or loss from film of small molecules acid causes the doping level reduction of polyaniline in use, and conductivity descends, and spectral quality changes.

The object of the present invention is to provide a kind of preparation method of new polyaniline self-assembled film.This method not only can be controlled the thickness of polyaniline at nanoscale, make the film and the substrate that make that stronger sticking power be arranged, also to overcome shortcomings such as the film properties short, preparation in polyaniline solutions work-ing life of Rubner method is stable inadequately, make the polyaniline solutions can life-time service, make performances such as the electricity of the film that makes and optics more stable simultaneously.

The substrate of self-assembled film of the present invention can be materials such as glass, pottery, silicon, various metal, various polymkeric substance.Assembling is preceding if substrate surface is not that tart carry out surface acidityization earlier.The method of acidification can adopt similar document [Science, volume was the 1232nd page in 1997 277] reported method, obtains acidic surface at substrate surface assembling one layer of polymeric acid molecule.The difference of the present invention and Rubner method maximum is that the polyaniline solutions that is used to assemble is the eigenmode polyaniline solutions, and this solution attitude of mixing under normal temperature condition is much solution-stabilized.Its benzene ring hydrogen of polyaniline used in the present invention both can be substituted by replacements such as other group such as methyl, ethyl, methoxyl group, oxyethyl groups yet.The solvent of dissolving polyaniline can be organic solvents such as N-Methyl pyrrolidone, N, dinethylformamide.In addition, the present invention's solution of being used to assemble also comprises polymeric acid solution.Used polymeric acid both can be organic polymer acid, as polystyrolsulfon acid, polyacrylic acid; Also can be inorganic polymer acid, as the isopoly-acid of molybdenum, heteropolyacid etc.Different with the Rubner method, do not add other small molecules acid in the polymeric acid solution.

The method of Rubner is based on the electrostatic attraction effect or the hydrogen bond action of doped polyaniline and polymer anion, and principle of the present invention is based on the doping reaction of eigenmode polyaniline and polymeric acid.Fig. 1 is a doping induction and deposition polyaniline self assembling process synoptic diagram, with the example that is assembled into of polyaniline/polystyrene sulfonic acid.After acid substrate is immersed in the solution of eigenmode polyaniline, the reaction of will mixing with the imine group of polyaniline in the solution of lip-deep acidic-group, thereby on substrate surface by chemical bond absorption last layer polyaniline, see Fig. 1 (1).After rinsing out unnecessary polyaniline with organic solvent, the skim polyaniline since the absorption on surface will be retained on the substrate surface.Thickness measuring is the result show, the thickness of individual layer polyaniline film can change in the scope of 1～20nm with the difference of polyaniline solutions concentration.Studies show that adsorbed polyaniline film is not fully mixed, after this film was immersed in the solution of polymeric acid, polyaniline can be aggregated thing acid and further mix, and makes it be converted into conductive state, adsorbs last layer polymeric acid molecule simultaneously, sees Fig. 1 (2).Because the multifunctional characteristic and the steric effect of polymeric acid, the surface of film will mainly be covered by acidic-group, and the surface is able to acidification again, makes continuation absorption from polyaniline solutions become feasible.Continue repeating step (1) (2), can obtain the multilayer polyaniline film.Concentration and assembling number of times by the control polyaniline solutions like this, thickness that just can controlling diaphragm.Because the deposition of each tunic is the spontaneous assembling process that the doping reaction of intrinsic polyaniline and polymeric acid causes, claim that present method is a doping induction and deposition polyaniline self-assembly method.

In sum, self-assembling method concrete steps of the present invention are as follows: 1. earlier substrate is carried out surface treatment, make its surface be acid; 2. acid substrate was immersed concentration and be in the solution of 0.01%～15% eigenmode polyaniline 1-30 minute, and after the taking-up, washed about 30 seconds, dry up, obtain the polyaniline self-assembled film of the eigenmode of individual layer with organic solvent; Rinse solvent can be a N-Methyl pyrrolidone, N, dinethylformamide, N,N-dimethylacetamide, tetrahydrofuran (THF) etc.3. to be immersed in concentration be in 0.01～10% the polymeric acid solution 5～120 minutes to the substrate that step 2 is obtained, and takes out, and with pure water rinsing about 30 seconds, dries up.Through this step, polyaniline is doped to conductive state, and the surface of film is again by acidification simultaneously; 4. repeating

step

2,3, can obtain the multilayer film of polyaniline.The concentration of control polyaniline solutions and assembling number of times can be at the thickness of nanoscale controlling diaphragm.

One of advantage of the present invention is to adopt the intrinsic polyaniline solutions to make the assembling raw material, because the eigenmode polyaniline solutions that adopts is more stable, has overcome that doped polyaniline is easy to sedimentary shortcoming in the Rubner method in assembling process, but the polyaniline solutions life-time service.Simultaneously, owing to do not use small molecules acid doping agent, the electricity of the film that makes and optical property are stable.

Another advantage of the present invention is to adopt means such as concentration that present method can be by selecting different polyaniline solution for use and assembling round-robin number of times, easily at the thickness of nanoscale controlling diaphragm.Between the film and substrate that is made by the present invention, film inner layer is that chemical bond is connected with interlayer, so film and substrate strong adhesion, and film is firm, fine and close.Be particularly suitable in various electron devices, using, as fields such as chemical sensor, electrochromic device chemically modified electrode, polymer field effect transistor.

The film that the present invention makes is that 450～650nm optical transmission window has higher transmittance at wavelength, and the transparency electrode and other optical coating that are suitable for use as luminescent device are used.

The surface of the film that the present invention makes has acidic-group, also can continue the film of other material of assembling on its surface, as polyelectrolyte, biologically functional molecule, conductive polymers, luminescent material, Nano semiconductor ion and soccerballene etc., perhaps at these material surface assembling polyaniline ultrathin membranes, can utilize the conductive characteristic of polyaniline and the special effects of other functional molecular, assemble nanometer composite superthin film in the nanoscale scope, construct novel nano electron device, have potential huge applications prospect.

Accompanying drawing and description of drawings:

The deposition synoptic diagram of the self-assembled film of Fig. 1 polystyrolsulfon acid/polyaniline

Wherein (1) expression is immersed substrate in the dilute solution of polyaniline; (2) expression is immersed substrate in the solution of polystyrolsulfon acid; (3) expression repeating step (1), (2); (4) be substrate; (5) be the molecular schematic diagram of polyaniline; (6) be the molecular schematic diagram of polystyrolsulfon acid.

The ultraviolet-visible absorption curves of the self-assembled film of Fig. 2 polystyrolsulfon acid/polyaniline is with the change curve of the assembling number of plies.The concentration of polystyrolsulfon acid, polyaniline is respectively 1% and 0.1%.Increase with the assembling number of plies is linear from scheming visible its absorbancy, illustrate that the amount of the polyaniline that each circulation is adsorbed is the same.Be also shown in from figure, very low in the absorbancy of 450～650nm film.

Embodiment: preparation polyaniline/polystyrene sulfonic acid self-assembled film

At first press the method for document (Science, volume was the 1232nd page in 1997 277) and assemble one deck polystyrene sulfonate film on quartz plate, making substrate surface is that sulfonic acid group covers, and is acid.The eigenmode polyaniline that chemical oxidization method is made is dissolved in the N-Methyl pyrrolidone, stirs 1 hour, filters, and obtains concentration and be 0.1% dilute solution.The substrate of acidification was immersed in this polyaniline solutions 10 minutes, takes out,, dry up with dimethyl formamide flushing 30 seconds.So just obtain the eigenmode polyaniline self-assembled film of individual layer.Continuation was immersed film in 1% the polystyrolsulfon acid solution 1 hour, took out, and used pure water rinsing, dried up, and just obtained individual layer doping type polyaniline self-assembled film, and thickness is about 5nm.The preparation of multilayer film is that this film is continued alternately to immerse in polyaniline and the polystyrolsulfon acid solution, through dimethyl formamide and pure water rinsing, dries up respectively.The specific conductivity of the film that obtains after 8 times of circulating is 0.01-1S/cm (specific conductivity is relevant with test environment humidity).The film cocoa that so makes stands the repeatedly flushing of current and its electric conductivity and absorption spectrum do not have considerable change.Thickness measuring is the result show, the thickness of film increases with the assembling number of times is linear.

If the concentration of the polyaniline solutions that adopts is respectively 0.05% and 0.2%, thick 2.5nm and the 11nm of being about respectively of then every tunic.

The film that adopts common casting method to make soaks several minutes and just can peel off from substrate in water, and the film that the present invention makes can stand the immersion and the flushing of water and organic solvent in the preparation process, illustrates to adopt prepared film of the present invention and substrate that stronger sticking power is arranged.

Claims

The manufacture method of 1 doping induction and deposition polyaniline self-assembling ultrathin film, it is characterized in that adopting intrinsic polyaniline solutions and polymeric acid is raw material, based on the doping prepared in reaction polyaniline ultrathin membrane of intrinsic polyaniline and polymeric acid, this manufacture method comprises the steps:

(1) earlier substrate is carried out surface treatment, make its surface be acid;

(2) acid substrate is immersed in the solution that concentration is 0.01%～15% eigenmode polyaniline 1～30 minute, after the taking-up, use N, dinethylformamide, N,N-dimethylacetamide, organic solvents such as tetrahydrofuran (THF) washed about 30 seconds, dried up, and obtained the polyaniline self-assembled film of the eigenmode of individual layer.

(3) to be immersed in concentration be in 0.01～10% the polymeric acid solution 5～120 minutes to the substrate that step 2 is obtained, and takes out, and with pure water rinsing about 30 seconds, dries up.Through this step, polyaniline is doped to conductive state, and the surface of film is again by acidification simultaneously;

(4) repeating step 2,3, can obtain the multilayer film of polyaniline.The concentration of control polyaniline solutions and assembling number of times can be at the thickness of nanoscale controlling diaphragm.
The manufacture method of 2 doping induction and deposition polyaniline self-assembling ultrathin films according to claim 1, it is characterized in that described intrinsic polyaniline comprises the coventional type polyaniline that polyaniline benzene ring hydrogen is not replaced by other group, also comprise the polyaniline that polyaniline benzene ring hydrogen is replaced by methyl, ethyl, methoxyl group, oxyethyl group.
The manufacture method of 3 doping induction and deposition polyaniline self-assembling ultrathin films according to claim 1, it is characterized in that described polyaniline solutions is that the eigenmode polyaniline is at N-Methyl pyrrolidone, N, dinethylformamide, N, the N-N,N-DIMETHYLACETAMIDE, the solution in one of organic solvents such as tetrahydrofuran (THF).