Solubility polyaniline sulfonic acid derivative

A number of water-soluble polyaniline derivatives have been developed in recent years. Incorporation of sulfonate groups onto the polymer backbone imparts water solubility to the polymer. In one process, this is accomplished by treating the polymer with fuming sulfuric acid which results in a sulfonic acid ring-substituted derivative that is alkali soluble but only upon conversion to the nonconducting sulfonate salt form. 

Polyaniline (PANI) can be formed by electrochemical oxidation of aniline in aqueous acid, or by polymerization of aniline using an aqueous solution of ammonium thiosulfate and hydrochloric acid. This polymer is finding increasing use as a "transparent electrode" in semiconducting devices. To improve processibiHty, a large number of substituted polyanilines have been prepared. The sulfonated form of PANI is water soluble, and can be prepared by treatment of PANI with fuming sulfuric acid (31). A variety of other soluble substituted AJ-alkylsulfonic acid self-doped derivatives have been synthesized that possess moderate conductivity and allow facile preparation of spincoated thin films (32). 

A second method of introducing sulfonate groups is accomplished by deprotonating polyaniline base and reacting with a sultone, i.e., 1,3-propanesultone [22]. This gives rise to an N-substituted polyaniline derivative that is water soluble. Another route involves the polymerization of sulfonated aniline monomer such as sodium salt of diphenylaminesulfonic acid [23]. 

Aside from considerations of the polymer form itself, polyaniline can be doped and derivatized in a variety of ways. First, polyaniline can be polymerized in the presence of a variety of acids, which critically influences the resulting electronic properties [1-15]. The particular acid used and polymerization process employed can affect the degree of crystallinity observed [10-15,17-29]. Multiple dopants and substitutions have been achieved in the hope of increasing both the conductivity and solubility of these materials. The derivatives are simple polyanilines functionalized with complex ions such as aryl-SOj, camphorsulfonates, and perfluoroalkyl (and aryl) sulfonates. Dopants vary from simple anions, to oxyanions, to the more typical iodide ions [10-15,17-29,38-44]. The functionalization and/or doping affects, the band population, and the polyaniline chain conformation in turn influence the resulting electronic and structural properties of the polymer. 

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