POLYANILINE COMPOSITIONS HAVING A SURFACE/CORE DOPANT ARRANGEMENT

Abstract: An electrically conductive polyaniline particle comprising a substituted or unsubstituted polyaniline doped with two or more dopants, at least one of said dopants predominating at or near the surface of said particles and at least one other dopant predominating at or near the core of said particle.

Description: POLYANILINE COMPOSITIONS HAVING A SURFACE/CORE DOPANT ARRANGEMENT BACKGROUND OF THE INVENTION This invention relates to novel electrically conductive polyaniline compositions. There has recently been an increased interest in the electrochemistry and electrical phenomena of polyaniline. See for example, U.S. Patent Nos. 3,963,498; 4,025,463; 4,855,361; 4,798,685; 4,806,271; 4,822,638; 4,851,487; 4,798,685; PCT O89/01694 and European Patent No. 0017717. SUMMARY OF THE INVENTION This invention relates to particles of a polyaniline doped with two or more dopants where the dopant at or near the surface of said particles is different from the dopant at or near the core of said particles. As used herein, "at or near the surface of the particle" is all or a portion of the surface of said particles to a depth of about 50A or less, and "at or near the core of said particle" is all or a portion of the particle more than about 50A from the surface of the particle. Several advantages flow from this invention. For example, through use of this invention, two or more dopants can be structured in the polyaniline particles to obtain better properties. For example, it is critically important to develop more thermally stable forms of polyaniline which are capable of being melt blended in matrix polymers with higher processing temperatures such as nylons and polycarbonates while at the same time providing a final blended composition having an acceptable level of electrical conductivity. WO 90/10297 published September 7 , 1990 and WO 89/101694 published February 23, 1989 identify a broad range of organic acids and their salts as thermally stable dopants for polyaniline. However, some of the most thermally stable dopants such as aryl disulfonates and trisulfonates of benzene and naphthalene exhibit significantly lower conductivity as compared to the less thermally stable dopants such as aryl monosulfonates. Particles in which the polyaniline is doped with dopants structured in a skin/core arrangement (or more generally in a stratified arrangement) can combine the high conductivity of one dopant (preferably in the core) with the high thermal stability of the other dopant (preferably in the skin) to provide a beneficial result. A variety of other desirable combinations of properties can be achieved through the skin/core or stratified polyaniline particles. For example, such particles can be used to enhance the dispersion ability of polyaniline particles doped in the core with desirable dopant in a matrix of polymers which is incompatible with the core dopant. This embodiment of the invention includes polyaniline particles doped predominantly in the skin or surface region of the particle with a dopant which has a more compatible surface energy with the intended matrix polymer or polymers of the blend but which may provide less electrical conductivity and which is doped predominantly in the core region with a dopant which provides higher levels of electrical conductivity. Other possible desirable features which can be incorporated via a surface dopant/core dopant combination is lessening the hygroscopic tendency of the more electrically conductive core dopant by using for example a luorinated alkyl sulfonate as the skin dopant and more high conductive toluene sulfonic acid as the core dopant. Still other desirable features which may be incoporated via a surface dopant/core dopant combination is the lessening of the reactivity of the doped polyaniline with contacting metals or with other chemical substances by using a less reactive surface dopant such as a polymeric sulfonate, and using a reactive dopant having a higher level of electrical conductivity predominantly in the core of the particle. This arrangement and combination of dopants provides particles and substrates comprising conductive polyaniline with the combinations of desirable features imparted by both dopants while minimizing or eliminating the undesirable of each if taken individually. DESCRIPTION OF THE PREFERRED EMBODIMENT BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood and further advantages will become apparent when references is made to the following detailed description of the invention and the accompanying drawings in which: Figure 1 is a graph of conductivity half life measured for a pellet of compressed polyaniline particles doped with tosylate anions. Measured half life at various temperatures (solid points) is used to project half life over a continuous range of temperature (solid line) . Figure 2 is a graph of conductivity half life versus temperature for a pellet of compressed polyaniline particles doped with tosylate, and a combination of tosylate and dodecylbenzene sulfonate in a skin/core configuration, where in the latter case the tosylate dopant predominates at the core and the dodecylbenzene sulfonate dopant predominates at the skin. Figure 3 is a graph of half-life versus temperature for polyaniline particles doped with tosylate, and a combination of tosylate and 1,5-n aphthalene disulfonate in a skin/core configuration, where in the latter case the tosylate dopant predominates at the core and the naphthalene disulfonate dopant predominates at the skin. DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention is directed to particles of a polyaniline doped with two or more dopants such that the concentration of at least one dopant at or near the surface of said particles is higher than the concentration of at least one other dopant at or near said core of said particle. Particle size and shape are not critical. For example, the particles can be of an irregular shape or can be of a regular or substantially regular shape. The particles can be regular flat shaped particles having relatively high aspect ratios or can be short block, spherical, oval or like shaped particles having relatively low aspect ratios. In any event, the shape of the particles will be dictated solely by the needs of the specific application. Particle size may also vary widely and is dependent on the particular application. In those applications where relatively large particles are required i.e. 1 to 100 microns, large particles are used; conversely in those applications where relatively small particles are required i.e. less than about one micron, small particles are used. Although not ciritcal,usually particles size is from about 0.05 to about 50 microns. Preferred particles sizes are from about 0.02 to about 3 microns. In some polyaniline compositions particles may exist as aggregates composed of smaller primary particles. It is generally most preferred for the production of uniform blends of high conductivity that these aggregates be broken down to their primary particles during compounding. It is most preferred that the primary particles themselves be doped in a skin/core configuration and that the primary particles range in size from about 0.05 to 0.2 microns. Polyanilines for use in the process of this invention may vary widely and include those derived from the polymerization of one or more unsubstituted and substituted anilines of the Formula I: Formula I wherein: n is an integer from 0 to 5; m is an integer from 0 to 5, with the proviso that the sum of n and m is equal to 5 and with the further proviso that at least one position on the aniline ring, preferably at the para position, is substituted with a substituent which will allow coupling of the aniline units such halo, hydrozen or other leaving group; Ri is the same or different at each occurrence and is selected from the group consisting of alkyl, deuterium, alkenyl, alkoxy, cycloalkyl, cycloalkenyl, alkanoyl, alkylthio, aryloxy, alkylthioalkyl, alkylaryl, arylalkyl, amino, alkylamino, dialkylamino, aryla ino, diarylamino, alkylarylamino, aryl, alkylsulfinyl, aryloxyalkyl, alkylsulfinylalkyl, alkoxyalkyl, phosphonic acid, alkylsulfonyl, arylthio, alkylsulfonylalkyl, boric acid, phosphoric acid, sulfinate salts, arylsulfinyl, alkoxycarbonyl, arylsulfonyl, carboxylic acid, phosphonic acid, halo, hydroxy, cyano, sulfinic acid, carboxylate salts, borate salts, phosphate salts, sulfonate salts, phosphinate salts, phosphonate salts, phosphonic acid, sulfonic acid, nitro, alkylsilane, or any of the foregoing aryl, aliphatic or cycloaliphatic groups substituted with one or more phosphonic acid, sulfonic acid, phosphoric acid, boric acid, carboxylate salt, borate salt, sulfonate salt, phosphinate salt, phosphonate salt, phosphate salt, phosphinic acid, carboxylic acid, halo, nitro, amino, alkylamino, dialkylamino, arylamino, diarylamino, alkylarylamino, cyano or epoxy moieties; or any two i groups together or any R 2 group together with any R 2 group may form a substituted or unsubstituted alkylene, alkenylene or alkynylene chain completing a 3, 4, 5, 6, 7, 8, 9 or 10 membered aromatic, heteroaro atic, heteroalicyclic or alicyclic ring, which ring may optionally include one or more divalent nitrogen, sulfur, sulfinyl, ester, carbonyl, sulfonyl, or oxygen atoms wherein permissible substituents are one or more phosphonic acid, sulfonic acid, phosphoric acid, boric acid, carboxylate salt, borate salt, sulfonate salt, phosphinate salts, phosphonate salt, phosphate salt, phosphinic acid, carboxylic acid, halo, nitro, amino, alkylamino, dialkylamino, arylamino, diarylamino, alkylarylamino, cyano or epoxy moieties ; or Rj. is an aliphatic moiety having repeat units of the formula: -(OCH 2 CH 2 )-0-CH 3 , -(0CH 2 CH(CH 3 ) )-0-CH 3 -(CH 2 )q CF 3 , -(CF 2 )_-CF 3 or -(CH 2 ) q CH 3 wherein q is a positive whole number; and R 2 is selected from the group consisting of permissible R x substituents or hydrogen. Illustrative of the polyanilines useful in the practice of this invention are those of the Formula II: wherein: n, m, R x and R 2 are as described above; x and y are the same or different at each occurrence and are integers equal to or greater than 0, with the proviso that the sum of x and y is greater than 0, preferably x is an integer equal to or greater than about 1 and/or the ratio of x to y is greater than or equal to about 0; and z is the same or different and is an integer equal to or greater than 1. Preferred for use in the practice of this invention are polyanilines of the above Formula II in which: n is an integer from 0 to 1; is an integer from 3 to 4, with the proviso that the sum of n and m is equal to 4; i is aryl, alkyl or alkoxy having from 1 to about 20 carbon atoms, sulfonic acid, halo, carboxylic acid, amino, carboxylate salt, alkylamino, phosphonate salt, dialkylamino, arylamino, phosphonic acid, boric acid, phosphate salt, phosphoric acid, borate salt, diarylamino, alkylarylamino, or alkyl or aryl substituted with carboxylic acid, phosphoric acid, boric acid, phosphate salt, phosphonic acid, borate salt, sulfonate salt, amino, alkylamino, dialkylamino, arylamino, diarylamino, alkylarylamino, carboxylate salt, halo, phosphonate salt, or sulfonic acid substituents; R 2 is the same or different at each occurrence and is a alkyl or hydrogen; x is an integer equal to or greater than 1; y is equal to or greater than 0, with the proviso that the ratio of x to y is greater than about 1; and z is an integer equal to or greater than about 5. More preferred for use in the practice of this invention are polyanilines of the above Formula II in which: n is an integer from 0 to 1; m is an integer from 3 to 4, with the proviso that the sum of n and m is equal to 4; i is aryl, alkyl, alkoxy, amino, alkylamino, dialkylamino, arylamino, diarylamino, alkylarylamino, halo, sulfonic acid, sulfonate salt, carboxylic acid or carboxylate salt, or alkyl or aryl substituted with one or more sulfonic acid, carboxylate salt, amino, alkylamino, dialkylamino, arylamino, diarylamino, halo, alkylarylamino, sulfate salt, sulfonate salt, or carboxylic acid substituents, wherein the aromatic moieties include from 6 to about 21 carbon atoms and the aliphatic moieties include from 1 to about 15 carbon atoms; R 2 is hydrogen; x is an integer equal to or greater than 2; y is equal to or greater than 1, with the proviso that the ratio of x to y is equal to or greater than about 2; and z is an integer equal to or greater than about 5. In the most preferred embodiments of this invention, the polyaniline is derived from unsubstituted aniline, alkoxy, alkyl, or sulfonic acid substituted aniline or copolymers thereof. The number of aniline repeat units is not critical and may vary widely. The number of aniline repeat units is preferably at least about 10, more preferably at least about 20, and most preferably at least about 30. Useful polyanilines can be prepared through use of chemical and electrochemical synthetic procedures. For example, of polyaniline can be prepared by chemically treating aniline with an oxidant such as ammonium persulfate (NH 4 ) 2 S 2 0 8 in excess acid such as IM HCl or electrochemically by the electrochemical oxidation of aniline in aqueous fluoroboric acid electrolyte on a platinum foil anode. The polyaniline is doped with a dopant solute which is derived from a compound, which upon addition to the polyaniline, ionizes the polymer with co-committent formation of a dopant solute species to form a charge transfer complex with polyaniline, which complex has a conductivity equal to or greater than about 10 "6 ohm "1 Cm "1 by the four-in-line probe method. Dopants for use in the practice of this invention can vary widely and can be such materials which are known in the art for use in doping conjugated backbone polymers. Illustrative of useful dopant species are oxidizing dopants such as AsF s , MoOCl 4 , MoCl 5 , PC1 5 , P0C1 3 , PCI 3 , A1C1 3 , N0 + and N0 2 + salts (such as NOBF 4 , N0PF β , N0SbF 6/ NOAsF 6 , NOCH 3 C0 2 , N0 2 BF 4 , N0 2 PF 6 , N0 2 AsF 6 , N0 2 SbF 6 , and N0 2 CF 3 S0 2 ) , HC10 4 , HN0 3 , H 2 S0 4 , benzoylperoxide, S0 3 , Br 2/ (FS0 3 ) 2 , ZnCl 2 , FS0 3 H, and Fe(III) salts (such as Fe(BF 4 ) 3 , FeBr 3 , Fe(CH 3 S0 3 ) 3 , Fe(C10 3 , FeCl 3 , Fe(OTs) 3 , and Fe(CF 3 S0 3 ) 3 which give rise to doped polymers containing dopant solutes such as N0 3 " , CH 3 S0 3 " , A1C1 4 " ,BF 4 " , ZnCl 4 " , PC1 4 " , PF 6 " , AsF 6 " , SbF 6 " , CF 3 S0 3 " , C10 4 ", OTs " , S0 3 '2 , C 6 H 5 C0 2 " , CH 3 S0 3 " , FS0 3 " , and FeCl 4 " and electrolyte salts such as LiC10 4 ,LiBF 4 , LiAsF 6 , NaPF 6 , BU 4 NCIO 4 , Bu^NOTs, Bu « NCF 3 S0 3 , LiCF 3 S0 3 , AgOTs, and the like. Illustrative of other dopants are inorganic oxidizing or non-oxidizing protonic acid dopants or organic such as hydrofluoric acid, hydrochloric acid, hydroiodic acid, phosphoric acid, nitric acid, perchloric acid, boric acid, sulfuric, and protonic acids such as those of the formula: R (P0 2 (Re)M) 8 (P0 3 M 2 ) £ (S0 3 M) β (C0 2 M) d (P0 2 M 2 ) t (S0 2 M) h or wherein: M is H*, or other metal or non-metal cation with the proviso that at least one of M is H* or a moiety which can be thermally or chemically transformed into a proton under use conditions, such as + NH 4 , + N(CH 3 ) 2 H 2 , + N(C 2 H 5 )H 3 and the like t is 0, 1, 2, 3 or 4; h is 1, 1, 2, 3 or 4; i is 1, 1, 2, 3 or 4; c is 0, 1, 2, 3 or 4; d is 0, 1, 2, 3 or 4; f is 0, 1, 2, 3 or 4; g is 0, 1, 2, 3 or 4, with the proviso that at least one of c, d, f, g, h, i or t is other than 0; e is 0, 1 or 2; R and R 5 are the same or different at each occurrence and are nitro, cyano, hydroxy, halo, amino, alkylamino, dialkylamino, arylamino, diarylamino, alkylarylamino, alkoxy, or salt substituted or unsubstituted alkoxy, aryl or alkyl having from 1 to about 30 carbon atoms wherein permissible substituents include sulfonate salt, perhaloalkyl, phenyl, alkoxy, halo, cyano, amino, haloalkyl, hydroxy, sulfonic acid, phosphoric acid phosphate salt, boric acid, sulfinate salt, phosphinate salt, sulfinic acid, borate salt, phosphinic acid, phosphonate salt, phosphonic acid, carboxylic acid, nitro, carboxylate salt and the like, or any two R 4 or any two R 5 substituents together may form an alkenylene chain completing a fused-ring system which chain may be unsubstituted or substituted with one or more halo, phosphoric acid, hydroxy, boric acid, nitro, cyano, amino, sulfinate salt, phosphinic acid, alkylamino, dialkylamino, phosphinate salt, arylamino, diarylamino, alkylarylamino, sulfinic acid, phosphate salt, carboxylate salt, phosphonic acid, phosphonate salt, sulfonate salt, borate salt, sulfonic acid or carboxylic acid groups, or R* or R 5 is a moiety of the formula: -(CH 2 ).CF 3 , -(CF 2 )-CF 3 , -(CH 2 )-CH 3 -(OCH 2 CH_) q OCH 3 or -(0CH 2 CH(CH 3 ) ) q OCH 3 wherein: q is a positive whole number from 1 to about 10; and Re is alkyl, aryl, aryloxy or alkoxy. In the more preferred embodiments of this invention, useful dopants are acids and/or acid derivatives of the formula: R* (P0 2 (Rg) M) g (P0 3 M 2 ) f (S0 3 M) c (C0 2 M) d or wherein: c, d, e, f and g are the same or different and are 0, 1 or 2, with the proviso that at least one of c, d, f and g is not 0; * and R s are the same or different at each occurrence and are alkyl, phenyl, amino, alkylamino, dialkylamino, arylamino, diarylamino, alkylarylamino, or alkyl substituted with one or more fluoro, sulfonic acid, sulfonate salt, alkoxy, carboxylate salt, hydroxy, nitro, cyano, phosphinic acid, phosphonic acid phosphinate salt, phosphonate salt, amino or carboxylic acid groups, or phenyl substituted with one or more alkyl, alkoxy, fluoroalkyl, sulfonic acid, phosphinic acid, phosphonic acid, phosphinate salt, phosphonate salt, sulfonate salt, carboxylate, hydroxy, nitro, cyano, or carboxylic acid groups or any two R 4 or R 5 substituents together may form an alkylene or alkenylene chain completing a naphthalene, anthracene or phenanthracene fused system which may be substituted with one or more alkyl, alkoxy, fluoro, phosphinic acid, phosphinate salt, phosphonic acid, phosphonate salt, fluoroalkyl, sulfonic acid, sulfonate salt, carboxylic acid, carboxylate salt, hydroxy, nitro, amino or cyano groups; R 6 is aryl, aryloxy, alkyl or alkoxy; and M is H + or other metal or non-metal cation, with the proviso that at least one of M is H + or is a moiety which can be thermally transformed into a proton under process conditions. In the process of the embodiment of this invention of choice, the dopant is a an acid of the formula: R 4 (S0 3 M) c (C0 2 M) d or wherein; c is 1, 2 or 3; e is 0, 1 or 2; R 4 is alkyl or alkyl substituted with one or more fluoro groups; R 5 is R 4 or any two R 3 groups together may form an alkenylene chain completing a naphthalene fused ring system which may be substituted with one or more sulfonic acid, sulfonic salt group or a combination thereof; and M is a proton, or other metal or non-metal cation, with the proviso that at least one of M is proton. Dopants which are preferred for use at or near the core of the conductive polyaniline particles of this invention when the purpose is to achieve high conductivity include but or not limited to methane sulfonic acid, trifluoromethane sulfonic acid, p-toluene sulfonic acid, 4-hydroxybenzene sulfonic acid, benzene sulfonic acid, and trifluoroacetic acid. Dopants which are preferred for use in this invention at or near the outer surface layer of the polyaniline particles of this invention to lesson thature of the partices and/or to increase compatibility between the particles and a matrix polymer of lower surface energy and lesser polar character include those which contain one or more alkyl or fluoroalkyl substituents of length equal to or greater than about 8 carbon atoms such as octylsulfonic acid, perfluorooctylsulfonic acid, dodecylsulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid and dodecyldiphenyl ether disulfonic acid. Dopants which are preferred for use at or near the surface of the particles to obtain more thermally stable compositions are aromatic, oligomeric or polymeric materials acids containing more than one sulfonic acid group such as 1,5-naphthalene disulfonic acid, 2,6-naphthalenedu sulfonic acid, dodecyldiphenyl ether disulfonic acid l-naphthol-3,6-disulfonic acid, diphenylether-4,4•-disulfonic acid, diphenylsulfone-4,4*-disulfonic acid, 2,5-dihydroxy-l,4-benzene disulfonic acid, 1,3,6-naphthalene trisulfonic acid, polyvinyl sulfonic acid, sulfonated polystyrene, sulfonated poly(4-vinyl naphthalene) , and the like. The amount of dopant added to the polyaniline at or near the surface of the particle or at or near the core of the particle is not critical and may vary widely. In general, sufficient dopant is added to the polyaniline such that the conductivity of at least about 10 "9 ohm "1 cm "1 , the upper level of conductivity is not being critical and is less than an amount which adversely affects the environmental stability of the polyaniline. The amount of dopant employed is sufficient to provide a conductivity preferably of at least about 10 "6 ohm "1 cm "1 more preferably of from about 10 " *ohm "1 cm "1 to about lO^ohm^cm "1 and most preferably of firm about 10 "3 ohm "1 cm "1 to about 10 +3 ohm "1 cm" 1 . The region or portion of the particles doped by a particular dopant and the selected dopant are critical. In general, the area at or near the surface of the particle is predominantly doped with a dopant that is "compatible" with the environment or matrix in which the particles will be dispersed and/or the conditions under which said particles will be dispersed. As used herein "compatibility" refers to the extent to which the dopant and the environment or matrix are misicible and include meeting one or more of the following criteria: closely matching the cohesive energies of the particle and the matrix; obtaining low, chemical reactivity between the particle and the matrix or other medium with which the particle will come in contact; and maximizing dispersive polar or hydrogen bonding interactions which will lead to the facile dispersion of the particles in the matrix. Additionally, when two or more dopants are employed it is preferred that the dopant at or near the surface be the most thermally stable of the dopants. The region of the particle at or near the core of the particle is doped with any kind of dopant, but is preferably doped with a dopant or mixture of dopants, which offers high conductivity and/or high thermal stability which may be "incompatible" with the environment in which the particle is used or is adversely affected by such environment (reduction in beneficial properties) to any extent. As used herein, "incompatible" is the opposite to compatible and refers to having a mismatched surface energy or a chemical reactivity toward the matrix or the environment in which the particle is embedded. The particles of this invention can be manufactured using modification of conventional chemical or electrochemical doping procedures such as those of U.S Patent 4,820,595. For example, particles of polyaniline can be prepared by addition of an oxidant to solutions of the aniline monomer. The dopant anion incorporated in the polyaniline may be derived from the oxidant (e.g. FeCl 4 " from FeCl 3 ) or it may be derived from an acid or salt which is also present in the solution (e.g., CH 3 (C 6 H 4 )S0 3 " when tosylic acid is present) during addition of an oxidant such as ammonium persulfate. Such conventional procedures produce doped conductive polyaniline particles and particle aggregates which are in general homogeneously doped with a dopant or mixture of dopants. In the present invention, such dopants or mixtures of dopants form the core of the conductive polyanilines particles. The outer layer or layers of the particles of this invention which contain dopant produced either during synthesis or after synthesis by dopant exchange or by partial dopant removal and replacement. It is possible to achieve a stratified dopant configuration by using an excess of a different salt or acid during the latter stages of the polymerization reaction. More preferred is to filter and wash the particles after the synthesis to remove any free salt or acid of the first core dopant type or depending on the degree of washing to remove a surface layer of the core dopant from each particle. A dopant layer of different composition can be then achieved by washing or slurrying the polymer particles in a solution of the new dopant. Repeatedly washing with different dopants will produce multiple layers. The electrically conductive polyaniline composition of this invention can be used for any purpose for which conductive polymers are useful. For example, the composition can be used to form electrically conductive articles for shielding purposes, anti-static purposes or adhesive. Examples of articles include conductive polymer housings for EMI Shielding of sensitive electronic equipment such as microprocessors, infrared, radio frequency and microwave absorbing shields, flexible electrically conducting connectors, conductive bearings, brushes and semiconducting photoconductor junctions, electrodes, capacitors, optically transparent or non-transparent corrosion-preventing coatings for corrodible materials such as steel, antistatic materials and optically transparent or non-transparent coatings for packaging electronic components, antistatic carpet fibers, waxes for floors in computer rooms, antistatic finishes for CRT screens, aircraft, auto windows, electostatic dissipative packaging for electronics, and the like. The particles of this invention are particularly suited for use in the manufacture of emulsions, suspensions of the polyaniline, blends of the polyaniline with other polymers as for example, other conjugated backbone polymers; thermoplastic polymers such as polyamides, polyphenylene oxides, polycarbonates, polyesters, polylactones, polyolefins, and polyacrylics; thermosetting resins such as phenolics and phenolic derivatives, alkyds, unsaturated polyester, epoxies, melamines, amino resins and allylics; and mixtures thereof. The following specific examples are presented to more particularly illustrate the invention, and should not be construed as being limitations on the scope and spirit of the inveNtion. EXAMPLE I Polyaniline (PAni) (320G) doped with para-toluene sulfonic acid (PTSA) (PAni-OTs) (approx. 8% S) was filtered on a Buchner funnel and was placed into a bucket, and 3 liters of 1 M PTSA having a concentration of 1 mol/L were added and stirred for 1/2 hour. The material was again filtered on the Buchner funnel. Then the filtrate was combined with 3 liters of boiling water and the mixture was stirred with an agitator/mixer for 10 minutes, then filtered on the Buchner funnel. The filter cake had a sulfur content of about 5 % by weight. A solution of methanol (2.5L) containing 2 weight % of para-dodecylbenzene sulfonic acid (DBSA) were added to the filter cake and stirred for 1/2 h. The mixture was then filtered again. The filtered material was dried in a fluid bed dryer at a maximum temperature of 80 °C. The skin/core particles, (PAni-tosylate (OTs)-dodecylbenzene sulfonate (DBS)), and polyaniline tosylate (PAni-OTs) particles were combined with matrix polymers, polycaprolactone (PCL) and poly(ethylene terephthalate glycol) (PETG) , into composites. The relative proportions of the polyaniline components were varied over a range of samples from about 50% by weight polyaniline to about 5% by weight. Conductivity of compression molded samples of each blend were measured by a four-probe technique. A plot of the logarithi of conductivity as a function of volume percent polyaniline gave an approximately "S" shaped curve in each case. Such characteristic "percolation" curves were analyzed to determine a "percolation point" (the point of steepest rise in conductivity) specified by the volume percent loading of polyaniline at that point, and the saturation conductivity as evidenced by the conductivity observed for the highest loading level for polyaniline in the blend. The results are set forth in the following Table II. In the Table, the conductivity of polyaniline is given in the first row and is that taken on a compressed pellet consisting of 100% polyaniline containing the specified dopant anion(s) . The saturation conductivity given in the bottom row refers to the blend with PETG. Table II Doped PAni Particles Property fPAni-OTs) fPAni-OTs/DBS) A. Conductivity of PAni 7.55 S/cm 4.5 S/cm B. Percolation Point in PCL 8% 8% C. Percolation Point in PETG 20-25% 9.5% D. Saturation Conductivity in PETG 5 x 10 " * S/cm 2.5 S/cm EXAMPLE . Polyaniline tosylate (PAni-OTs) was prepared from aniline, p-toluene sulfonic acid (PTSA) , and ammonium persulfate solution by first combining the aniline and the acid, and then slowly adding the ammonium persulfate solution to the acid and aniline solution in approximately one hour. The solids which were formed were then filtered and washed successively twice with water (75 β C) , once with 5% solution of PTSA (slurry for 1 to 2 hrs) , and finally with a 2% solution of PTSA in methanol. After filtration, the solids were dried in a vacuum oven at 130 β C until the temperature of the powdered solids reached 110 β C. The water content of the solids was determined to be less than 3% by weight. EXAMPLE 3 Polyanilinium tosylate coated by dodecylbenzene sulfonate (PAni OTs/DBS) was prepared as in Example 2 with the exception that dodecylbenzene sulfonic acid (DBSA) was substituted for the PTSA in the final methanol wash. By elemental analysis the resulting dried powder was found to contain approximately (by molar ratio) 70% OTs and 30% DBS. Since exposure of PAni OTs to a concentrated solution of DBSA will cause the replacement of PTSA with DBSA via a process which requires the outward diffusion of PTSA and the inward diffusion of DBSA, the above process produced a polyaniline which was preferentially doped on the surface of each powder grain and/or primary particle with DBSA. EXAMPLE 4 Polyaniline tosylate coated by naphthalene disulfonate was prepared by the procedure of Example 3 wherein naphthalene disulfonic acid (NDSA) was substituted for PTSA only in the final methanol wash and this wash was maintained at 75 β C. EXAMPLE 5 Polyaniline tosylate heavily exchanged with dodecylbenzene sulfonate (PAni-OTs/DBS (heavy) and polyaniline tosylate heavily exchanged with naphthalene disulfonate (PAni-OTs/NDS (heavy)) where prepared in the manner of Example 2, with the exception that DBSA and NDSA were substituted for PTSA in the final two washes, the first was being made at 75°C. EXAMPLE 6 The relative thermal stabilities of the various forms of polyaniline, described in Examples 2-5 above, were determined by the following procedure: The - powdered polyaniline was compressed into pellets with a diameter of 0.7 cm and a thickness of about 0.09 cm. The pellets were placed in an apparatus in which the given pellet was contacted by gold pins at four equally spaced points (90 degrees apart) near the circumference of the pellet. In this configuration a four-probe resistance measurement could be made which could be used to calculate the bulk conductivity of the pellet from the equation s=0.215/(Rd) , where s is conductivity in S/cm (or ohm^cm "1 ) , R is resistance in ohms, and d is pellet thickness in cm. The pellet was maintained in an atmosphere of flowing nitrogen and was held at various constant temperatures (130°C, 150°C, 170°C, 200 β C, and 230 β C) while the conductivity was observed to decay. In order to insure that all samples were thoroughly dry, the pellets were first held at 150°C for 16 hours before conductivity data were taken. All of the samples exhibited a decay in conductivity as an exponential function of time at a given temperature which could be described by the relation, s(t) = s-e- (t t) * where s(t) is the conductivity at a time, t; s 0 is the initial conductivity at time t = 0; t is an experimentally determined characteristic decay time; and a is an experimentally determined parameter for a given sample at each temperature. The value of a typically lay in a range from 0.77 to 1.0. With the help of this equation a charateristic half-life of the conductivity can be determined at each temperature from the value of t and a determined at that temperature according to the relation. ιz = (ln2) 1/β where In is the naperian logarithm and t 12 is the time required for the conductivity to decrease by half (half life) . Since the determination of t and a can be made from the functional form of the decay at early times, this method does not require that the conductivity be driven down to one half its original value at each temperature. As a result, this method allows the determination of the half lives at the five temperatures listed above on the same sample without unduly altering the thermal decay characteristics of the sample by heavily degrading the sample at each temperature. The following Table II summarizes the results obtained for the various polyaniline samples. In the Table II, the abbreviations have the following meanings: (a) "PAni-OTS" is polyaniline doped with tosylate as in Example 2. (b) "PAni-OTS/DBS" is skin/core polyaniline particles doped with tosylate at the core and doped with dodecylbenzene sulfonate at the skin as in Example 3. (c) "PAni-OTs/DBS (heavy) " is polyaniline heavily doped with dodecylbenzene sulfonate as in Example 5. (d) "PAni-OTS/NDS" is skin/core polyaniline particles doped with tosylate at the core and doped with naphthalene disulfonate at the skin as in Example 4. (e) "PAni-OTs/NDS (heavy) " is polyaniline heavily doped with naphthalene disulfonic acid as in Example 5. Table II Conductivity Half Lives of Polyaniline Compositions Composition s 0 t 1/2 (170°C) t 1/2( 200°C) t 1 / 2 (230°C) (S/cm) (h) (h) (h) The conductivity given in the Table II, s , is that obtained at 150°C after drying 16 hours at 150°C. The conductivity half lives, t 1/2 , are those measured at 170°C, 200 β C, and 230°C. The data are arranged in order of thermal stability at the highest temperature 230°C. The data for the samples having a skin/core arrangement of different organic sulfonate dopant anions illustrate a synergy of desirable properties which goes beyond a simple average. The core and skin combination of PTSA and DBSA, respectively, (PAni OTs/DBS) results in a conductive polyaniline which combines the higher thermal stability of PAni/DBS with the high conductivity of PAni/OTs. Likewise, the PAni OTs/NDS sample combines the high conductivity of PAni/OTs with a significant improvement in the thermal stability stemming from its skin of the dopant, NDSA, even though this sample received only a light treatment with NDSA in the final wash. The sample PAni OTs/NDS (heavy) shows an even more substantial increase in thermal stability. For comparison with the results of Table II, a sample of polyaniline doped with hydrochloric acid was also tested. This sample was treated at temperatures below 100°C because it was to resistive to measure at temperatures above 100°C. The initial conductivity offer drying at 90°C was 2.9 S/cm. Example 7 The data for the half lives taken as in Example 6 at 130°C, 150°C, 170°C, 200°C, 230°C was shown to follow an Arrhenius exponential as a function of temperature of the form, where e is the base of the naperian logarithm and K is the Boltz ann constant. The activation energy, E,, was determined from the slope of a plot of ln[t 12 ] vs the inverse of absolute temperature in degrees Kelvin. The naperian logarithm of the prefactor, ln[( fcl/2) o3, was determined from the intercept at 1/T=0. These empirically determined parameters were then used to predict the thermal stability (i.e., the conductivity half life) over a range of temperature extending from 50 β C to about 280°C. The agreement between the predicted variation of half-life and data taken for PAni-OTs is shown in Figure 1 projected results are given in Figure 2 for PAni OTs, PAni-OTs/DBS and PAni-OTs/DBS (heavy) . Figure 3 compares the projected results obtained for PAni-OTs, PAni-OTs/NDS and PAni-OTs/NDS (heavy) . These figures illustrate that the thermal stability for the samples with a skin/core dopant arrangement is enhanced beyond a simple averaging of properties. These data were used to estimate an upper limit for processing termperature (T p ) and for continuous use temperature (T u ) . Temperatures corresponding to maximum processing times of 0.1 h and l.Oh were calculated along with the temperatures where the continuous use time was 5 years. Table III below summarizes the results obtained for the various compositions which were tested. TABLE III Use Temperature and Processing Temperatures of Polyaniline Compositions

Claims: WHAT IS CLAIMED IS: 1. An electrically conductive polyaniline particle comprising a substituted or unsubstituted polyaniline doped with two or more dopants, at least one of said dopants predominating at or near the surface of said particles and at least one other dopant predominating at or near the core of said particle wherein said polyaniline is a polyaniline homopolymer or copolymer of the type derived from polymerizing an aniline of the formula: n is an integer from 0 to 5; m is an integer from 0 to 5, with the proviso that the sum of n and m is 5; R x is phosphinic acid, phosphonic acid, sulfonic acid, boric acid, phosphoric acid, alkylamino, dialkylamino, arylamino, diarylamino, alkylarylamino, amino, sulfonate salt, borate salt, hydroxy, phosphonate salt, phosphinate salt, phosphate salt, sulfinic acid, nitro, sulfinate salt, carboxylic acid, halo, carboxylate salt, cyano, deuterium, or substituted or unsubstituted alkyl, alkenyl, alkoxy, cycloalkyl, cycloalkenyl, alkanoyl, alkylthio, alkynyl, dialkylamino, arylamino, diarylamino, alkylarylamino, aryloxy, hydroxy, alkylthioalkyl, alkylaryl, arylalkyl, aryloxy, amino, alkylthioalkyl, alkylaryl, arylalkyl, alkylsufinyl, alkoxyalkyl, alkylsulfonyl, aryl, arylthio, arylsulfinyl, alkoxycarbonyl, alkylsilane, or arylsulfonyl, wherein permissible substituents are one or more amino, phosphinate salt, alkylamino, dialkylamino, arylamino, diarylamino,phosphinic acid, alkylarylamino, phosphonic acid, sulfonic acid, boric acid, sulfinic acid, sulfinate salt, phosphoric acid, sulfonate salt, borate salt, carboxylate salt, phosphonate salt, phosphate salt, carboxylic acid, halo, nitro, hydroxy, cyano or epoxy moieties; or any two R 3 substituents or any one R 3 substituent and R 2 substituent taken together may form substituted or unsubstitued alkylene, alkynylene or alkenylene chain completing a 3, 4, 5, 6, 7, 8, 9 or 10 membered aromatic, heteroalicyclic, heteroaromatic or alicyclic carbon ring, which ring may optionally include one or more divalent ester, carbonyl, nitrogen, sulfur, sulfinyl, sulfonyl or oxygen wherein permissible substituents are one or more amino, alkylamino, phosphinic acid, phosphinate salt, dialkylamino, arylamino, diarylamino, alkylarylamino, phosphonic acid, sulfonic acid, boric acid, sulfinic acid, sulfinate salt, phosphoric acid, sulfonate salt, borate salt, carboxylate salt, phosphonate salt, phosphate salt, carboxylic acid, halo, nitro, hydroxy, cyano or epoxy moieties, or R 3 is an aliphatic moiety having repeat units of the formula: (OCH 2 CH 2 ) q 0-CH 3 , (OCH 2 CH(CH 3 )) q O-CH 3 , (CH 2 ) q CF 3 , (CF 2 ) q CF 3 or (CH 2 ) q CH 3 wherein q is a positive whole number; and R 2 is the same or different at each occurrence and is alkyl or hydrogen. 2. The particle according to claim 1 wherein said homopolymer or copolymer is of the formula II: x and y are the same or different at each occurrence and are integers equal to or greater than 0, with the proviso that the sum or x and y are greater than 0; and z is an integer equal to or greater than about 1. 3. The particle according to claim 2 wherein m is from about 3 to about 4. 4. The particle according to claim 3 wherein Rj. is the same or different at each occurrence and is alkyl or alkoxy having from 1 to about 20 carbon atoms. 5. The particle according to claim 4 wherein x is an integer equal to or greater than 1; y is equal to or greater than 0, with the proviso that the ratio of x to y is greater than about 0; and z is an integer equal to or greater than about 5. 6. The particle according to claim 5 wherein: n is 0; m is 4; x is an integer equal to or greater than 2; y is equal to or greater than 0, with the proviso that the ratio of x to y is greater than about 0.5; and z is an integer equal to or greater than about 5. 7. The particle according to claim 1 wherein said polyaniline is doped with one or more organic acid dopants or salts thereof of the formula: R 4 (P0 2 (Re)M) g (P0 3 M 2 ) f (S0 3 M) c (C0 2 M) d (P0 2 M 2 ) t (S0 2 M) h (PO(R 6 )) or wherein: M is H*, or other metal or non-metal cation with the proviso that at least one of M is H + or a moiety which can be thermally or chemically transformed into a proton under use conditions, such as t is 0, 1, 2, 3 or 4 i is 0, 1, 2, 3 or 4, h is 1, 1, 2, 3 or 4; c is 0, 1, 2, 3 or 4, d is 0, 1, 2, 3 or 4, f is 0, 1, 2, 3 or 4j g is 0, 1, 2, 3 or 4 with the proviso that at least one of t, i, h, c, d, f or g is other than 0; e is 0, 1 or 2; and R*, R 5 and Re are the same or different at each occurrence and are nitro, cyano, hydroxy, halo, amino, alkylamino, dialkylamino, arylamino, diarylamino, alkylarylamino, alkoxy, or salt substituted or unsubstituted alkoxy, aryl or alkyl having from 1 to about 30 carbon atoms wherein permissible substituents include sulfonate salt, perhaloalkyl, phenyl, alkoxy, halo, cyano, amino, haloalkyl, hydroxy, sulfonic acid, phosphoric acid phosphate salt, boric acid, sulfinate salt, phosphinate salt, sulfinic acid, borate salt, phosphinic acid, phosphonate salt, phosphonic acid, carboxylic acid, nitro, carboxylate salt and the like, or any two R 4 or any two R 5 substituents together may form an alkenylene chain completing a fused-ring system which chain may be unsubstituted or substituted with one or more halo, phosphoric acid, hydroxy, boric acid, nitro, cyano, amino, sulfinate salt, phosphinic acid, alkylamino, dialkylamino, phosphinate salt, arylamino, diarylamino, alkylarylamino, sulfinic acid, phosphate salt, carboxylate salt, phosphonic acid, phosphonate salt, sulfonate salt, borate salt, sulfonic acid or carboxylic acid groups, or R 4 or R 5 is a moiety of the formula: -(CH 2 ) q CF 3 , -(CF 2 ) q CF 3 , -(CH 2 ) q CH 3 -(0CH 2 CH 2 ) q 0CH 3 or -(0CH 2 CH(CH 3 ))-0CH 3 wherein: q is a positive whole number from 1 to about 10. 8. The particle according to claim 9 wherein said dopant is a sulfonic acid, sulfonic acid derivative or a combination thereof of the formula: R (S0 3 M) c (C0 2 M) d or wherein; c and d are the same or different and are 0, 1, 2 or 3 with the proviso that at least one of c or d is other than 0; e is 0, 1 or 2; R 4 is alkyl or alkyl substituted with one or more fluor substituents; R 5 is alkyl or alkyl substituted with one or more fluoro, or any two R 5 groups together may form an alkenylene chain completing a naphthalene faced system which may be substituted with one or more sulfonic acid, hydroxy, phenoxy, or sulfophenoxy, fluoro or alkyl group; and M is a proton, or other metal or non-metal cation, with the proviso that at least one of M is proton. 9. The particle according to claim 8 wherein said polyaniline is unsubstituted polyaniline and at least one of said dopants predominating at the core of said particle is selected from group consisting of methane sulfonic acid, trifluoromethane sulfonic acid, p-toluene sulfonic acid, 4-hydroxybenzene sulfonic acid, benzene sulfonic acid, and trifluoroacetic acid. 10. The particle according to claim 8 wherein said compatibility enhancing dopants is selected from the group consiting of octylsulfonic acid, perfluorooctylsulfonic acid, dodecylsulfonic acid, dodecylbenzenesulfonic acid, dmonylnaphthalenesulfonic acid, dodecyldiphenyl ether disulfonic acid, 1,5-naphthalene sulfonic acid, 2,6-naphthalene sulfonic acid, l-naphthol-3,6-disulfonic acid, diphenylether-4,4'-disulfonic acid, diphenylsulfone-4,4'-disulfonic acid, 1,3,6-naphthalene trisulfonic acid, and 2,5-dihydroxy-l,4-benzene disulfonic acid.

Inventors: ELSENBAUMER RONALD L, HAN CHIEN-CHUNG, MILLER GRANVILLE G, SHACKLETTE LAWRENCE W, WEBLING BERNHARD M, ELSENBAUMER, RONALD, L., HAN, CHIEN-CHUNG, MILLER, GRANVILLE, G., SHACKLETTE, LAWRENCE, W., WEBLING, BERNHARD, M.
Applicants: ALLIED SIGNAL INC, ALLIED-SIGNAL INC.
Application year: 1992
Main classification: C08G73
IPC codes: C08G73, C08L79, H01B1