EP2038326A1

EP2038326A1 - Novel compositions and method for the production thereof

Info

Publication number: EP2038326A1
Application number: EP07788801A
Authority: EP
Inventors: Heikki Tenhu; Sami-Pekka Hirvonen; Juha Hartikainen
Original assignee: Panipol Oy
Current assignee: Panipol Oy
Priority date: 2006-07-12
Filing date: 2007-07-12
Publication date: 2009-03-25
Also published as: CN101516959A; WO2008006945A1; FI20060681A0; FI20060681L

Abstract

A solution of an inherently conductive polymer, such as polyaniline or poly(thiophene)s in a polar solvent, a method of its preparation and the use of the solution. According to the 5 invention, the polymer is doped with a sulphonated polymer containing aromatic repeating units which form a rigid or semi-rigid backbone. The sulphonated polymer forms a doped, conductive complex with a polymer comprising a conjugated polymeric chain and it contains a sufficient amount of free sulphonic groups to maintain the complex in solution. The novel solutions can be used for producing conductive films, for coating various substrates 10 and for producing electrically conductive ink formulations for printed electronics applications.

Description

NOVEL COMPOSITIONS AND METHOD FOR THE PRODUCTION THEREOF

Background of the Invention

Field of Invention

The present invention relates to inherently conductive polymers and their uses. More particularly, it relates to novel aqueous solutions of inherently conductive polymers and to methods for the preparation thereof. The present invention also concerns the use of the aqueous solutions for forming films and coating layers.

Description of Related Art

Electronic components are easily damaged in the case of rapid discharging of the electrostatic current (electrostatic discharge, ESD), causing insulating areas and other defects in the conductive patterns. Therefore, electronic components and devices are often packed in electrically conductive packages that have optimally surface resistance in the range of 10⁶-10⁹ ohm. Due to the large conductive surface of the package, possible electric charges are discharged in a controlled manner, without damaging the components.

One of the most common materials for protecting electronic components and devices against damages caused by ESD is plastic, that can be in various forms such as rigid film or flexible foil. A typical way to make such packaging materials electrically conductive is by mixing carbon black or other conductive fillers into the polymer matrix. However, conductive fillers may migrate to the surface of the package and cause contamination of the product.

Additionally, fillers do not allow the control of the conductivity, but lead easily to highly conductive materials that are not optimal for ESD protection. Furthermore, most fillers lead to non-transparent materials.

Another option would be conductors based on ionic conductivity, which is well known technology for antistatic applications. However, in this case the conductivity often requires conditions with high relative humidity of the air and the conductivity is often lost by time. Also, the level of conductivity is restricted in the lower end of the ESD protection, maximum surface resistance being typically 10⁸ - 10⁹ ohm.

Also paper and cardboard are often used as packing material for electronic components and devices. Paper as such has surface resistance of 10⁹-10¹⁰ ohm. However, this resistance is achieved only at high air humidity.

There is a need for a way of modifying packaging materials in such a way as efficiently to render them electrically dissipating to avoid electrostatic discharge phenomenon. In particular, there is a need for improved ways of modifying materials by solvent coating which is a convenient way of treating various, potentially even irregularly shaped surfaces.

A particularly interesting group of materials for improving the resistance against ESD of packaging materials is formed by the inherently conductive polymers (ICPs). The ICPs are polymers which typically are "doped" (furnished, processed) in order to generate charge carriers (holes and electrons). Common to all electrically conductive polymers are the conjugated double bonds of the backbone chain (alternate single and double bonds, delocalized π electron system), which enable the movement of the charge carriers. Electrically conductive polymers have both ionic and electronic conductivity. The conductivity of electrically conductive polymers can be regulated within the whole conductivity range, from an insulating material to a metallic conductor.

However, the ICPs are generally poorly soluble in solvents and it is therefore difficult to formulate them for solvent application.

Summary of the Invention

Based on the above, it is an aim of the present invention to provide a novel composition of inherently conductive polymers in solution phase.

It is a second object of the invention to provide an improved method of producing solutions and dispersions of inherently conductive polymers. It is a third object of the invention to provide uses of the novel compositions.

These and other objects, together with the advantages thereof over known compositions and methods, are achieved by the present invention as hereinafter described and claimed.

According to the invention, a solution of an inherently conductive polymer in a polar solvent, is provided. In this kind of a solution, the inherently conductive polymer is present in the form of a complex formed by a polymer chain with conjugated double bonds and a polymeric, sulphonated doping agent generally comprising a rigid or semi-rigid backbone. Preferably the doping agent has a backbone containing aromatic repeating units. In order to achieve a reasonably good dissolution of the complex into the solvent phase and to maintain the complex in solution, according to the invention, there are at least some free sulphonic acid groups present on the polymeric doping agent.

For the purpose of the present invention, generally any inherently conductive polymer can be used provided that it can be reversibly doped. In this context, "doped" stands for a capability of the polymer to be complexed, oxidised or protonised or charged into conductive form. The polymers have a polymer chain with conjugated double bonds. Typically, inherently conductive polymers are insoluble in solvents, in particular in organic solvent and in solvents having a solubility parameter of <11 (cal/cm³)¹⁷².

The present compositions can be produced by forming

- a solution of a sulphonated polymer, which contains aromatic repeating units forming a rigid or semi-rigid backbone, is mixed with monomers of a polymer comprising a polymeric chain with conjugated double bonds, and

- the monomers are in situ polymerized in the presence of the sulphonated polymer.

The novel compositions have a number of interesting and important uses including antistatic coatings for electronics packages and conductive patterns in printed electronics applications.

More specifically, the present compositions are characterized by what is stated in the characterizing part of claim 1. The novel method according to the invention is characterized by what is stated in the characterizing part of claim 10 and the uses by what is stated in claims 19 to 22.

Considerable advantages are achieved by the present invention. Thus, by the present invention packaging materials can easily be treated and coated by applying a conductive polymer in liquid (solution) form on the surface thereof. Further, various conductive thin films can be formed from the solution phase by evaporating the solvent of the composition. Inherently conductive polymers can be incorporated into water-borne paint compositions comprising, e.g. an acrylic binder. Toxic solvents and high VOC solvents can be avoided. The process according to the present invention is uncomplicated and economical.

Typically, dispersions of polyaniline are manufactured by a multi-step process, where aniline is first polymerized, then polyaniline particles are isolated from the reaction medium and the particles are re-dispersed in the selected solvent. This is not an optimal way to produce homogenous and stable polymer dispersions. The clear advantage of the present invention is that polymerization takes place in-situ in the presence of the soluble doping acid, which leads to highly homogenous, nanoscale dispersion of polyaniline in the selected solvent.

Next the invention will be examined more closely with the aid of the following detailed description.

Description of Preferred Embodiments

As discussed above, the present invention provides a novel composition comprising a solution of an inherently conductive polymer in a polar solvent. The polymer is doped with a sulphonated polymer containing aromatic repeating units which form a rigid or semi-rigid backbone. Further, there is a sufficient amount of free sulphonic acid groups present on the sulphonated polymer residue for maintaining the complex in solution, i.e. in solvent phase.

According to a first preferred embodiment, the doped, conductive complex of the sulphonated polymer is formed with a polymer comprising a conjugated polymeric chain. In general, all polymers are suitable that are convertible via a reversible oxidation or reduction and/or via reversible protonisation or other deriving reactions (which can, to some extent, be described as a complexing or compensation reaction) into conjugated, positive or negative polymer chains, the charging of which is compensated by ions of the opposite charge. Thus, as a result, the polymer can exist in states of different conductivity, which normally have a different chemical composition. Polymers having a conductivity which can reach more than 10^~2 S/cm are preferred.

Examples of useful polymers include polydiacetylene, polyacetylene (PAc), polypyrrole (PPy), polyaniline (PAni), polythiophene (PTh), polyisothianaphthene (PITN), polyheteroarylenvinylene (PArV), in which the heteroarylene group can be, e.g. thiophene or pyrrole, poly-p-phenylene (PpP), polyphenylensulphide (PPS), polyperinaphthaline (PPN), polyphthalocyanine (PPhc) and other conjugated polymers, their derivatives (i.e. polymers of derivatives e.g. substituted with side-chains on the ring or on the heteroatom [these derivatives being] of the monomers forming the above mentioned polymers) and their copolymers and their physical mixtures with each other.

In particular, the conjugated polymeric chain is selected from the group of polyaniline, polypyrrole and substituted poly(thiophene)s. Preferably, the inherently conductive polymer is a doped complex of polyaniline, based on aniline or aniline derivatives as monomers, or poly(ethylenedioxythiophene). Polyaniline is particularly preferred.

The polar solvent is, in particular, water or an alkanol (aliphatic alcohol) or mixtures thereof, such as aqueous solutions of alkanols. Examples of suitable aliphatic alcohols are methanol, ethanol, n- and isopropanol, n-, i- and t-butanol, amyl alcohol and n-hexanol. Many of the alkanols can be employed in the form of aqueous solutions having a concentration of alkanol of about 0.1 to 99.5 %, in particular about 0.5 to 98 % by volume of the total solution. Examples include aqueous solutions of C_1-^ alkanols, e.g. one or several of the above mentioned lower alkanols, having a concentration of about 5 to 99 % by volume with respect to the alkanol.

The present compositions can be characterized as true solutions in the respect that they are optically clear and translucent. Typically, however, the conductive complexes are present in the form of dispersed minute particles. Thus, the present aqueous or alkanolic solutions comprise particles of doped polyaniline having a hydrodynamic radius of 10 to 300 nm, in particular about 190 - 250 nm. With particles having a particles size in the indicated range, colloidally stable dispersions are obtained.

The concentration of the doped polymer in the liquid phase can vary in broad ranges depending on the conductive complex and on the concentration of the free sulphonic acid groups. Generally, there is about 0.1 to 30 %, in particular about 0.5 to 10 %, by weight of doped polymer in the solution. The sulphonated polymer contains about 0.01 to 1.5, in particular about 0.6 to 1.0, free sulphonic acid groups per repeating unit in the solution phase.

According to the method of the present invention for producing a solution of an inherently conductive polymer in a polar solvent comprises in combination the steps of

- mixing a solution of a sulphonated polymer, which contains aromatic repeating units forming a rigid or semi-rigid backbone, with monomers of a polymer comprising a polymeric chain with conjugated double bonds, and

- in situ polymerizing the monomers in the presence of the sulphonated polymer. A conductive complex is thus formed and the sulphonic acid groups assist in maintaining the conductive complex in the solution after in situ polymerization.

Generally, the sulphonation agent is a polymer, which contains aromatic repeating units forming a rigid or semi-rigid backbone to form a sulphonated polymer which contains 0.1 to 0.95 sulphonic acid groups per repeating units of the polymer.

Examples of suitable polymers include poly(phenylene oxide), (poly(3, 5 -dimethyl- 1,4- phenylene oxide) and poly(phenylene sulphide) which are sulphonated as known per se, e.g. by contacting the polymer in a non-polar solvent with a sulphonating agent such as fuming sulphuric acid or mixtures of sulphuric acid and nitric acid. Other examples include aromatic polyimides, polymers of the Kevlar® type and poly(ether-ether-ketones). Before employing the sulphonated polymer as a doping agent it is purified and isolated from the sulphonation medium. Another option is to use the purified solution of the sulphonated polymer directly in the aniline polymerization process. The polymer can for example be dialyzed against the polar solvent to remove residues of the sulphonation agent. In practice, a solution of a sulphonated polymer is first prepared, containing about 0.1 to 15 %, in particular about 0.2 to 5 %, by mass of the sulphonated polymer in a polar solvent and the polymer is then contacted in the polar solvent with about 1:100 to 100:1, preferably about 1:10 to 5:1, in particular about 1:5 to 1:1, parts by weight of monomers of the inherently conductive polymer backbone. The monomers are polymerized in the presence of an oxidative catalyst, such as various persulphate compounds (e.g. ammonium persulphate, APS).

The in situ polymerization is carried out, preferably under agitation, in the presence of the sulphonated polymer at a temperature in excess of -20 ⁰C up to about 50 ⁰C, preferably at a temperature in the range of from -5 to 30 ° C, in particular at about 0 to 25 ⁰C. Polymerization is continued to obtain a conversion rate of at least 20 % (calculated from the weight of the monomers), in particular at least 40 %, preferably at least 60 % and advantageously at least 80 %.

As a result of the process described above, a conductive polymer complex is obtained in liquid phase, in which the polymeric components have a weight average molecular weight of about 1,000 to 250,000 g/mol, in particular about 5,000 to 100,000 g/mol, preferably about 10,000 to 50,000 g/mol.

The conductivity of the polymer complexes varies over a large range depending on the components (the polymer/doping agent) and their concentrations. Generally, the conductivities are greater that 1*10 ⁸ S/cm, in particular greater than 10^~6 S/cm, and preferably about 1*10 ⁴ to 10 S/cm, e.g. about 5*10 ⁴ to 1*10 ^J S/cm.

Of the above solvents, water is particularly interesting. According to a preferred embodiment, the present invention comprises the following steps for producing novel aqueous compositions:

- sulphonating a rigid, aromatic mainchain polymer to produce a sulphonated polymer which is soluble in water,

- recovering the sulphonated polymer in aqueous phase,

- admixing in the aqueous phase monomers of an inherently conductive polymer,

- adding a polymerization catalyst, - polymerizing the monomers to obtain a conversion ratio of at least 50 %, calculated from the weight of the added monomers, to produce a conductive polymeric complex, and

- recovering the conductive polymeric complex.

The novel compositions have several interesting uses.

Thus, with a composition according to the present invention it is possible to coat plastic packaging materials with a conductive polymer at the ideal surface resistance range of 10⁶-10⁹ ohm. The advantage is also that inherently conductive polymers are permanently conductive and independent of the air humidity. Furthermore, such coatings are transparent. By coating paper or cardboard with a water soluble inherently conductive polymer of the present kind, it is possible to obtain permanent ESD protection for package applications.

In addition to packages, the products according to the present invention can be employed in applications that are used in explosive sensitive environment. As an example, lighting systems can be coated with a transparent layer of electrically conductive polymer, which prevents the formation of a dangerous discharge of the antistatic electricity.

Also ESD paint and lacquer formulations for usage in antistatic applications are possible by using the invention in question. Furthermore, dust sensitive applications, such as protective plastic films of displays, can be treated with the present water soluble inherently conductive polymer. Due to the reduced static electricity, dust formation would be less than for untreated plastic films.

Another application area of the present invention is in the field of printed electronics. Traditionally, electronics relies strongly on silicon based semi-conductors. However, there are applications where silicon based technology has clear restrictions. As an example, in some cases physical flexibility is required from the electronic component. With silicon based technology this is difficult to achieve, due to the rigid nature of the silicon materials. Also, silicon based electronics is complicated to manufacture, which increases the unit price of the components. By using water soluble inherently conductive polymers, it is possible to print thin conductive patterns that are fully polymeric, flexible and semi-conductive. The thickness of the patterns can be 1 micrometre or less, typically about 1 to 1000 nm. Standard printing technologies can be used, such as gravure printing, screen printing and ink-jet printing. Therefore, high volume, low-cost production of electronic devices is possible. Examples of such printed electronics applications are various radio frequency identification (RFID) systems, memory elements, electrodes, supercondensators and photovoltaic devices, among others.

Also, water based solutions of inherently conductive polymers could be applied in sensors, such as biosensors, where electrical conductivity and its changes may be used as an indicator of e.g. chemical reactions, acidity changes and humidity changes. The present invention allows for the manufacture of such sensors by low-cost, commonly used printing methods.

The following non-limiting examples illustrate the invention:

1. SULPHONATION REACTIONS

1.1 Reaction materials and methods

Materials

Poly(2,6-dimethyl-l,4-phenylene oxide) i.e. PDMPO was obtained from Aldrich (M_w 220 000 g/mol)¹. Polyphenylenesulfide (PPS) was obtained from Aldrich (M_n 10 000 g/mol)². Fuming sulfuric acid containing 20 % of SO₃ was obtained from Riedel-de Haen. Chloroform (HPLC grade) was purchased from Lab-scan and dried on molecular sieves 4 A. Methanol (HPLC grade) was provided by Chromanorm. Concentrated sulphuric acid was obtained from AnalaR (sc. grade). Dialysis tubes used were Cellu sep MWCO 6000-8000 or 3500 provided by Orange Scientific.

¹ Determined with static light scattering from toluene solutions

² Announced by supplier Characterization

Sulphonation degree was determined from dry polymer by back titration with 0.100 M NaOH and 0.100 M HCl solutions.

1.2 Sulphonation of poly(2,6-dimethyl-l,4-phenylene oxide) (PDMPO)

METHOD A

Poly(2,6-dimethyl-l,4-phenylene oxide) was sulphonated in chloroform solution using fuming sulfuric acid containing 20 % SO₃ as a sulphonating agent. 20 g of poly(2,6-dimethyl-l,4- phenylene oxide) was dissolved in 500 ml of dry chloroform in a two necked 1 L flask with mechanical stirring. Stirring speed was adjusted to 450 rpm. 10 ml of fuming sulfuric acid was added in the solution drop-wise at room temperature. The reaction was then continued for 18 hours. After 24 hours of total reaction time, 300 ml of methanol was added to cease the reaction and chloroform was removed using rotary evaporation. Sulphonated poly(2,6- dimethyl-l,4-phenylene oxide) was dialyzed against distilled water in Cellu sep-tubes MWCO 6000-8000 to remove remaining sulfuric acid. Dialysis was continued until the dialysis water remained neutral. The sulphonated polymer could not be precipitated from its water solution and was therefore recovered by lyophilization. Sulphonation ratio³ was varied between 0.50 and 0.90 by changing the amount of fuming sulfuric acid and sulphonation time.

METHOD B

Sulphonation was carried out as in method A, but the product was not lyophilized. The sulphonated polymer was stored as water solution. The polymer concentration and the degree of sulphonation were determined from dried sample.

SO₃ units per aromatic ring of PDMPO METHOD C

Sulphonation was carried out as in method A, but the dialysis of the product was conducted in methanol. The dialyzed product was then stored as methanol solution or dried from methanol, first by evaporation in normal pressure to a solid substance and then in dynamic vacuum to remove any residual solvent.

1.3 Sulphonation of polyphenylenesulfide (PPS)

METHOD A

5 g of poly(l,4-phenylene sulfide) powder was dispersed in 100 ml of 96 % H₂SO₄ solution with magnetic stirring. The suspension was placed in an oil bath at 75 ⁰C and 20 ml of fuming sulfuric acid with 20 % of SO₃ was added in the solution at once. The reaction was continued for 22 hours and was stopped by pouring the reaction mixture in 300 ml of distilled water. The sulphonated polymer precipitated and was removed from the solution by centrifugation. The precipitated polymer in suspension was dialyzed in Cellu sep-tubes MWCO 6000-8000 against distilled water to remove remaining sulfuric acid. During the dialysis the precipitated polymer dissolved completely to form totally transparent yellow-orange liquid in the tubes. Different degrees of sulphonation were achieved by varying the amount of fuming sulfuric acid in sulphonation as well as sulphonation time.

METHOD B

Sulphonation was carried out as in method A, but the product was not lyophilized. The sulphonated polymer was stored as water solution. The polymer concentration and the degree of sulphonation were determined from dried sample. 2. ANILINE POLYMERIZATION

2.1 Reactants and methods

Materials

Aniline and ammoniumpersulphate i.e. APS (pro analysi grade) were obtained from Merc and used as received.

Characterization

Electrical conductivity of the polyaniline complexes was measured by four-probe method from the films cast on the glass plates equipped with (sputtered) gold electrodes. Particle size of the polymer dispersions in water was analysed by dynamic light scattering in water solutions.

METHOD A

Aniline was polymerized by chemical polymerisation in a 250 ml round bottle flask equipped with a magnetic stirrer in room temperature (22 ⁰C). First, a predetermined amount of the selected doping acid was dissolved in 50 ml of 1 M hydrochloric acid and mixed for 2 hours. Next, a calculated amount of aniline was added to the reaction mixture and mixing was continued until the aniline had dissolved. Finally, calculated amount of APS dissolved in 20 ml of 1 M hydrochloric acid was added in the solution during a period of 1 h. Mixing was continued for 4 or 5 hours at room temperature. The product was purified by dialysis against water until the water remained neutral.

EXAMPLE 1

Synthesis of PDMPO-S A9-P ANI-I

Method A was used to prepare polyaniline complex with (PDMPO-SA9) with a sulphonation ratio of 0.80. Thus, 0.400 g of PDMPO-SA9 was dissolved in 50 ml of 1 M hydrochloric acid in a 250 ml round bottomed flask with magnetic stirring. After 2 hours 0.164 g of aniline was dissolved in the solution. Then, 0.400 g of ammonium persulfate (APS) was dissolved in 20 ml of 1 M hydrochloric acid and added to the reaction solution during a period of 1 h. The reaction was allowed to continue for a further 4 hours and after that the solution was purified by dialysis against distilled water. Dialysis was continued until the water remained neutral and the dialyzed product was transferred to storage.

Measured conductivity for PDMPO-S A9-PANI-1 is 6 10 ,-3 o S cm -1

EXAMPLE 2 Synthesis of PDMPO-SAlO-P ANI-I

Method A was used to prepare polyaniline complex with (PDMPO-SAlO) with a sulphonation ratio of 0.70. According to that method, 0.400 g of PDMPO-SAlO was dissolved in 50 ml of 1 M hydrochloric acid in a 250 ml round bottomed flask with magnetic stirring. After 2 hours 0.148 g of aniline was dissolved in the solution. Then, 0.365 g of APS was dissolved in 20 ml of 1 M hydrochloric acid and added to the reaction solution during a period of 1 h. The reaction was allowed to continue for a further 4 hours and after that the solution was purified by dialysis against distilled water. Dialysis was continued until the water remained neutral and the dialyzed product was transferred to storage.

Measured conductivity for PDMPO-SAlO-P ANI-I is 1-10^"3 S cm^"1

EXAMPLE 3

Synthesis of PDMPO-S Al l -PANI-I

Method A was used to prepare polyaniline complex with (PDMPO-SAl 1) with a sulphonation ratio of 0.60. Following that method, 1.00 g of PDMPO-SAl 1 was dissolved in 50 ml of 1 M hydrochloric acid in a 250 ml round bottomed flask with magnetic stirring. After 2 hours, 0.333 g of aniline was dissolved in the solution. Then, 0.814 g of APS was dissolved in 20 ml of 1 M hydrochloric acid and added to the reaction solution during a period of 1 h. The reaction was allowed to continue for another 4 hours and after that the solution was purified by dialysis against distilled water. Dialysis was continued until the water remained neutral and the dialyzed product was transferred to storage. Measured conductivity for PDMPO-SAl 1 -PANI-I is 4-10^"3 S cm^"1

METHOD B

Aniline was polymerized by chemical polymerisation in a 250 ml round bottle flask equipped with a magnetic stirrer at room temperature (22 ⁰C). First, a predetermined amount of the selected doping acid was dissolved in distilled water and mixed for 2 hours. Next, the calculated amount of aniline was added to the reaction mixture and mixing was continued until the aniline had dissolved. Finally, the calculated amount of APS dissolved in distilled water was added to the solution.

EXAMPLE 4

Synthesis of PDMPO-SA 12-P ANI-I

Method A was used to prepare polyaniline complex with (PDMPO-SA12) with a sulphonation ratio of 0.80. Accordingly, 1.00 g of PDMPO-SA12 was dissolved in 40 ml of distilled water in a 250 ml round bottomed flask with magnetic stirring. After 2 hours 0.331 g of aniline was dissolved in the solution. Then, 0.810 g of APS was dissolved in 10 ml of distilled water and added to the reaction solution in a period of 1 h. The reaction was allowed to continue for another 4 hours and after that the solution was purified by dialysis against distilled water. Dialysis was continued for 20 h and the dialyzed product was transferred to storage.

EXAMPLE 5 Synthesis of PDMPO-SA 12-P ANI-2

Example 4 was repeated, but the amount of aniline was changed to 0.248 g and the amount of APS to 0.607 g. EXAMPLE 6

Synthesis of PDMPO-SA 12-PANI-3

Example 4 was repeated, but the amount of aniline was changed to 0.414 g and the amount of APS to 1.013 g. The product obtained was a viscous solution.

EXAMPLE 7

Synthesis of PDMPO-SA 12-PANI-4

Example 4 was repeated, but the amount of aniline was changed to 0.496 g and the amount of APS to 1.213 g. The product obtained was a viscous solution.

METHOD C

Aniline was polymerized by chemical polymerisation in a 250 or 500 ml round bottle flask equipped with a magnetic stirrer in room temperature (22 ⁰C). First, the calculated amount of aniline was dissolved in a predetermined amount of the selected doping acid solution, which was obtained from the dialysis procedure without lyofilization. Finally, the calculated amount of APS dissolved in distilled water was added to solution.

EXAMPLE 8

Synthesis of PDMPO-S A21 -P ANI-2

Method C was used to prepare polyaniline complex with (PDMPO-SA 12) with a sulphonation ratio of 0.80. Thus, 8.00 g (165 ml) of PDMPO-SA21 as water solution was placed in a 500 ml round bottomed flask with magnetic stirring. Then, 2.6 g of aniline was dissolved in the solution. APS (6.36 g) was dissolved in 40 ml of distilled water and added to the reaction solution within one hour. The reaction was allowed to continue for another 4 hours and after that the solution was purified by dialysis against distilled water. Dialysis was continued for 10 hours and the dialyzed product was transferred to storage. EXAMPLE 9

Synthesis of PPS-SA3-P ANI-I

Method C was used to polymerize polyaniline complex with (PDMPO-SA12) with a sulphonation ratio of 0.50. According to that method, 1.03 g (50 ml) of PPS-SA3 in the form of an aqueous solution was placed in a 250 ml round bottomed flask equipped with magnetic stirring, and 0.268 g of aniline was dissolved in the solution. Then, 0.656 g of APS was dissolved in 5 ml of distilled water and added to the reaction solution within an hour. The reaction was allowed to continue for another 4 hours and after that the solution purified by dialysis against distilled water. Dialysis was continued for 10 hours and the dialyzed product was transferred to storage.

METHOD D

Aniline was polymerized by chemical polymerisation in a 1000 ml reactor equipped with a cooling mantel and a magnetic stirrer at 0 ⁰C. First, the calculated amount of aniline was dissolved in the selected doping acid solution, which was obtained via sulphonation method B. Finally, the calculated amount of APS was dissolved in distilled water and added to the solution.

EXAMPLE 10

Synthesis of PDMPO-S A23k-P ANI-I

Method D was used to prepare polyaniline complex with (PDMPO-SA23k) with a sulphonation ratio of 0.90. Firstly, 5.00 g (107 ml) of PDMPO-SA23k as aqueous solution was placed in a 1000 ml round bottomed reactor equipped with a cooling mantel and a magnetic stirrer. Then, 1.54 g of aniline was added to the solution. Next, APS (4.15 g) was dissolved in 20 ml of distilled water and added to the reaction solution within one hour. The reaction was continued for another 16 hours, after which the solution was purified by dialysis against distilled water. Dialysis was continued for 10 hours and the dialyzed product was transferred to storage.

Measured conductivity for PDMPO-S A23k-PANI-1 is 8,5 -10^"2 S cm^"1 METHOD E

Aniline was polymerized by chemical polymerisation in a 250 ml round bottle flask equipped with a magnetic stirrer at room temperature (22 ⁰C). First, a predetermined amount of the selected doping acid was dissolved in methanol and mixed for 1 hour. Next, a calculated amount of aniline was added to the reaction mixture and mixing was continued until aniline was fully dissolved. Finally, calculated amount of APS was dissolved in water and added to the solution drop-wise. Mixing was continued for overnight (16 h) at room temperature. The product was purified by dialysis against methanol until the solution remained neutral.

EXAMPLE 11

Synthesis of SA15_PANI_5

Method E was used to prepare polyaniline complex with (PDMPO-SAl 5) with a sulphonation ratio of 0.95. Firstly, 2.00 g of PDMPO-SAl 5 was dissolved in 40 ml of methanol and placed in a 250 ml round bottomed flask equipped with a magnetic stirrer. Then, 0.65 g of aniline was added to the solution. Next, APS (1.75 g) was dissolved in 10 ml of distilled water and added to the reaction solution within an hour. The reaction was continued for another 16 hours and after that the solution was purified by dialysis against methanol. Dialysis was continued for 10 hours and the dialyzed product was transferred to storage.

METHOD F

Aniline was polymerized and purified as in example E, except the solvent used was ethanol instead of methanol.

EXAMPLE 12 Synthesis of SA20_PANI_2

Method F was used to prepare polyaniline complex with (PDMPO-SA20) with a sulphonation ratio of 0.70. Thus, 2.00 g of PDMPO-SA20 was dissolved in 40 ml of ethanol and placed in a 250 ml round bottomed flask equipped with a magnetic stirrer. Then, 0.56 g of aniline was dissolved in the solution. Next, APS (1.75 g) was dissolved in 10 ml of distilled and added to the reaction solution within an hour. The reaction was continued for another 16 hours and after that the solution was purified by dialysis against methanol. Dialysis was continued for 10 hours and the dialyzed product was transferred to storage.

Claims

Claims:

1. A solution of an inherently conductive polymer in a polar solvent, said polymer being doped with a sulphonated polymer containing aromatic repeating units which form a rigid or semi-rigid backbone, said sulphonated polymer containing a sufficient amount of free sulphonic groups to maintain the complex in solution.

2. The solution according to claim 1, wherein the sulphonated polymer forms a doped, conductive complex with a polymer comprising a conjugated polymeric chain.

3. The solution according to claim 2, wherein the conjugated polymeric chain is selected from the group of polyaniline, polypyrrole and substituted poly(thiophene)s.

4. The solution according to any of the preceding claims, wherein the inherently conductive polymer is a doped complex of polyaniline, based on aniline or aniline derivatives as monomers, or poly(ethylenedioxythiophene).

5. The solution according to any of claims 1 to 4, wherein said polar solvent is selected from the group of water and alkanols and mixtures thereof.

6. The solution according to any of claims 1 to 5, wherein the concentration of the doped polymer is about 0.1 to 30 %, in particular about 0.5 to 10 %, by weight of the solution.

7. The solution according to any of claims 1 to 6, comprising particles of doped polyaniline having a hydrodynamic radius of 10 to 300 nm, in particular about 190 - 250 nm, to provide a colloidally stable dispersion.

8. The solution according to any of claims 1 to 7, wherein the sulphonated polymer contains about 0.01 to 1.5, in particular about 0.6 to 1.0, free sulphonic acid groups per repeating unit in the solution phase.

9. The solution according to any of the preceding claims, wherein the sulphonated polymer is poly(phenylene oxide) or poly(phenylene sulphide).

10. A method of producing a solution of an inherently conductive polymer in a polar solvent, comprising

- in situ polymerizing the monomers in the presence of the sulphonated polymer to produce a conductive complex of the polymeric chain with conjugated double bonds and the sulphonated polymer, said sulphonated polymer containing a sufficient amount of sulphonic acid groups to maintain the conductive complex in the solution after in situ polymerization.

11. The method according to claim 10, comprising sulphonating with a sulphonation agent a polymer, which contains aromatic repeating units forming a rigid or semi-rigid backbone to form a sulphonated polymer which contains 0.1 to 0.95 sulphonic acid groups per repeating units of the polymer.

12. The method according to claim 11, wherein the sulphonated polymer is dialyzed against the polar solvent to remove residues of the sulphonation agent before the polymer is contacted with said monomers of the polymer having a chain with conjugated double bonds.

13. The method according to any of claims 10 to 12, comprising preparing a solution of a sulphonated polymer containing about 0.1 to 15 %, in particular about 0.2 to 5 %, by mass of the sulphonated polymer in a polar solvent and contacting the polymer in the polar solvent with about 1:100 to 100:1, preferably about 1:10 to 5:1, in particular about 1:5 to 1:1, parts by weight of said monomers.

14. The method according to any of claims 10 to 13, wherein the polar solvent comprises water, an alkanol or a mixture thereof.

15. The method according to any of claims 10 to 14, comprising polymerizing the monomers in the presence of an oxidative catalyst.

16. The method according to any of claims 10 to 15, comprising polymerizing the monomers in the presence of the sulphonated polymer at a temperature in excess of -20 °C up to about 50 °C, preferably at a temperature in the range of from -5 to 30 ° C, in particular at about 0 to 25 ^°C.

17. The method according to any of claims 10 to 16, comprising preparing a conductive polymer complex, in which the polymeric components have a weight average molecular weight of about 1,000 to 250,000 g/mol, in particular about 5,000 to 100,000 g/mol, typically about 10,000 to 50,000 g/mol.

18. The method according to any of claims 10 to 17, comprising the steps of

- recovering the sulphonated polymer in aqueous phase, - admixing in the aqueous phase monomers of an inherently conductive polymer,

- adding a polymerization catalyst,

- polymerizing the monomers to obtain a conversion ratio of at least 50 %, calculated from the weight of the added monomers, to produce a conductive polymeric complex, and - recovering the conductive polymeric complex.

19. Use of a solution according to any of claims 1 to 9 for producing conductive films.

20. Use of a solution according to any of claims 1 to 9 for coating of substrates selected from the group of polymeric films and sheet, and paper and cardboard webs and sheets.

21. Use of a solution according to any of claims 1 to 9 for producing electrically conductive paint compositions.

22. Use of a solution according to any of claims 1 to 9 for producing electrically conductive ink formulations for printed electronics applications.