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the problem of redoping. One approach is to attach a functional group on the polymer backbone. For example, sulfonic functional groups have been attached to polyaniline backbone to provide water solubility3 . In other examples, long-chain alkyl groups have been attached to increase organic solvent solubility4 . While the solubility was improved, the optical and electrical properties of polyaniline were somewhat compromised. Perhaps the delicate one-dimensional structure of delocalized w electrons is substantially perturbed by the covalently attached functional groups. In yet another approach, the conductive form was solubilized in organic solvents by using a bulky organic dopant such as camphor sulfonic acid, or other surfactant-like molecules5 . This approach avoids covalently attaching a functional group to polyaniline and achieved solubility by concealing the ionic group under the shield of the bulky organic group. The surface of the doped polymer becomes more hydrophobic and allows solvation in organic solvents. In this article we present a different approach to solubilize polyaniline. This approach involves a new synthetic method to assemble a polymeric complex between polyaniline and a polymeric dopant. The advantage of this new approach is that in addition to providing solubility in water and polar organic solvents, it offers ease in adjustment of the degree of solubility and simultaneously allows molecular engineering to satisfy other materials requirements (such as material stability, mechanical strength, processability) which were traditionally viewed as conflicting with the need for preserving the electronic and optical properties of conducting polymers. A new soluble polyaniline: A polymeric complex In this article we report the use of a polymeric molecular complex that consists of two strands twisted together: Strand 1 is polyaniline, abbreviated as Poly(An). Strand 2 is an anionic polyelectrolyte, abbreviated as Poly(E). Such a double-stranded polymer, abbreviated as Poly(An):Poly(E), is pictured in Fig. 1. One might draw a lose analogy of this polymeric complex with the doublestranded DNA, with the Poly(An)

caution that the pairing between two strands is expected to be much less ordered and less specific than that of a DNA molecule. The presence of the Fig. 1 A molecinlar r-amplLx pol-y(An):poly(E) second strand in the complex provides sites for chemical modification to satisfy multiple demands on materials properties in a single molecule. Since chemical modification at these sites on the second strand would not disturb the delicate one-dimensional electronic structure of polyaniline, the problem of conflicting requirements described in the preceding section is relaxed if not entirely removed. In this complex, one strand is used as a vehicle for carrying the electronic and optical properties and the other strand is used as a vehicle for optimizing structural features that are needed for processability, durability and for mechanical strength. We will discuss how the double-stranded complex can be use