Compositions – Electrically conductive or emissive compositions
Reexamination Certificate
2000-04-17
2003-10-14
Kopec, Mark (Department: 1751)
Compositions
Electrically conductive or emissive compositions
C252S519200, C546S008000
Reexamination Certificate
active
06632380
ABSTRACT:
This application is the national phase of international application PCT/98/04660 filed Jul. 24,1998 which designated the U.S.
The invention relates to chemical compounds of intrinsically conductive polymers, in particular polyanilines, with metals, their preparation and uses of these compounds.
Compounds of conjugated and intrinsically conductive polymers, such as polyanilines (poly-phenylenamines), with metals are not yet known.
“Conjugated and intrinsically conductive polymers” which are a component of the compounds according to the invention are understood as those organic polymers and derivatives thereof which have polyconjugated bond systems (e.g. double bonds, aromatic or heteroaromatic rings or triple bonds). Examples of such polymers are polydiacetylene, polyacetylene (PAc), polypyrrole (PPy), polyaniline (PAni), polythiophene (PTh), polyisothianaphthene (PITN), polyphenylenevinylene, polyheteroarylenevinylene (PArV), it being possible for the heteroarylene group to be e.g. thiophene or pyrrole, poly-p-phenylene (PpP), polyphenylene sulphide (PPS), polyperinaphthalene (PPN), and derivatives thereof (which are built up e.g. from substituted monomers), copolymers thereof with other monomers and physical mixtures thereof. They can exist in various states, which are described by in each case different empirical formulae and can be converted into one another usually substantially reversibly by (electro)chemical reactions, such as oxidation, reduction, acid/base reaction or complex formation. These reactions are occasionally also described in the literature as “doping” or “compensation”, or can be regarded as “charging” and “discharging” analogously to the electrochemical processes in batteries. At least one of the possible states has a very good electrical conductivity, e.g. has a conductivity of more than 1 S/cm (as the pure substance), so that they can be referred to as intrinsically conductive polymers.
A good overview of intrinsically conductive polymers which have already been synthesized and are suitable according to the invention is to be found in Synthetic Metals, issues 17, 18 and 19 (1987) and vol. 84-86 (1997).
Such conductive polymers have also already been used in the metallization of printed circuit boards (see WO-A-97/20084). They have also found use in corrosion protection (see WO-A-95/00678).
The invention is based on the object of providing electrically conductive compounds, the conductivity of which is less sensitive to changes in pH than that of conventional conductive polymers and which show advantages over conventional conductive polymers in their use in the production of printed circuit boards or in corrosion protection.
This object is achieved by the compounds disclosed herein. The invention also relates to the process for making such compounds and to the uses of these compounds for metallizing substrates, in printed circuit boards and for protection of metal surfaces from corrosion.
The compounds according to the invention are those of intrinsically conductive polymers with metals. Compounds of this type are not yet known.
It has been found that intrinsically conductive polymers surprisingly can form true chemical compounds with metals, and the polymer-metal compounds prepared are also electrically conductive.
On the basis of the investigations carried out, it is assumed that the compounds are built up in the manner of a copolymer of the following general formula (I).
[(
DU
)
a−x
(
Me
a+
)
x
(
DU
ox
H
+
)
y
](
a·x+y
)
A
−
(I)
wherein
DU=a dimer unit of the polymer,
DU
ox
=an oxidized form of the dimer unit,
Me
a+
=a metal ion of valency a,
a=the valency of the metal ion,
x=an integer from 1 to 10,000,
y=an integer from 0 to 10,000,
A=an anion.
It is further assumed that the metal is bonded chemically to the dimer unit, and that each dimer unit is capable of bonding a monovalent metal ion. For bonding of a divalent metal ion, on the other hand, at least two dimer units are required. The dimer units can also be present in doped form. Examples of dimer units DU are given below for polypyrrole, polythiophene, polyacetylene and polyaniline.
Possible anions are, in particular, monovalent anions, such as chloride, toluenesulphonate or dodecylbenzenesulphonate. Polyvalent anions are also possible, but these are then present in a correspondingly lower number.
Accordingly, preferred compounds of polyaniline with iron and copper probably correspond to the following formulae (II) and (III).
As a rule, the metals are present in the compounds according to the invention as mono- or polyvalent positive ions, the exact oxidation level not being essential for the invention but depending on the surrounding conditions. The metal can also have the oxidation level of zero e.g. as a result of an internal redox reaction with the polymer.
However, those polymers which are built up by the “shish-kebab” principle, i.e. in which the electron-rich monomer units are stacked on top of one another, such as e.g. in polyphthalocyanines, are unsuitable as polymers according to the invention.
It has not yet been possible to clarify the nature of the chemical bond between the metal and the polymer in the compounds. It could possibly be a complex bond. At any rate, stoichiometrically defined compounds with a content of from just above zero up to 50 mol % of a monovalent ion, up to 25 mol % of a divalent ion etc., based on the moles of monomer in the polymer, are possible.
Only intrinsically conductive polymers in which electron-rich structural elements such as double bonds or aromatic or heteroaromatic ring systems overlap and which have been rendered conductive by protonation with Brönstedt acids or oxidation with Lewis acids, i.e. by a so-called doping, are as yet known in the prior art. However, no compounds in which chemical bonds exist between the polymer and a metal as in the compounds according to the invention are as yet known.
The compounds according to the invention preferably contain as the metal iron, copper, zinc, magnesium, cadmium or tin. Iron and copper are particularly preferred here.
Polyacetylene, polypyrrole, polythiophene, polyphenylenevinylene and, in particular, polyaniline are preferred as the intrinsically conductive polymer.
The compounds according to the invention are preferably in the form of dispersions in aqueous or organic dispersing agents or in the form of paints or polymer blends containing them. In addition to the compounds according to the invention the polymer blends comprise further polymers, copolymers or polymer mixtures, such as polyamides, polyesters, polyethers, such as polyethylene oxides, copolymer latices on an aqueous basis, such as vinyl acetate/butyl acrylate, or other copolymer latices, and/or polyvinyl alcohols. Particularly preferred further polymers are polyamides.
Furthermore, preferred compounds are those of polyaniline with copper, iron or zinc, which, as dispersions in N-methylpyrrolidone and iso-propanol, on spectroscopic analysis in the UV-VIS-NIR range, have absorption maxima at wavelengths of
copper-polyaniline compound
285 ± 5 nm,
iron-polyaniline compound
280 ± 5 nm,
zinc-polyaniline compound
332 ± 5 nm.
The metal-polymer compounds according to the invention can be prepared by a process in which
(a) a dispersion of an intrinsically conductive polymer is brought into contact with the chosen metal in elemental form, wherein
(b) the dispersion medium is agitated in order to ensure exchange of matter at the interface between the metal and dispersion, and
(c) the dispersion is brought into contact with the metal until the metal-polymer compound has formed.
Re (a): Possible dispersions are those in water or aqueous solvents or in organic solvents. Suitable dispersion are described e.g. in WO-A-97/20084 and DE-C-38 34 526. The metal is employed in elemental form, e.g. in the form of foils, sheets or granules.
Re (b): It is essential that the dispersion medium is agitated, since otherwise only deposition of
Kopec Mark
Pillsbury & Winthrop LLP
Zipperling Kessler & Co. (GmbH & Co.)
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