CHARACTERIZATION AND SOLID-STATE PROPERTIES OF PROCESSABLE N-ALKYLATED POLYANILINES IN THE NEUTRAL STATE

Incorporation of flexible alkyl chains into polyaniline was accomplish ed through an N-alkylation method with the leucoemeraldine form in ord er to maximize the degree of alkylation. The number of carbons varied from butyl to octadecyl, and with dodecylated samples, the degree of s ubstitution was also controlled. The solubility in common organic solv ents improved remarkably with the alkylation. The polymers displayed i nteresting solvatochromism and thermochromism, which result from the c onformational changes induced by the interactions between the polymer and the solvent molecules and from the cooperation of disordering of t he side chains and twisting in the main chain upon heating. In the sol id state, the polymers form a layered structure in which the distance between the backbones depends on the length of alkyl side chain as rec orded by the d spacing in WAXD patterns. DSC studies revealed that gla ss and melting transitions decreased systematically by increasing the length of substituents. With increasing side-chain length, the degree of interdigitation increases and the side chains begin to crystallize in a hexagonal packing array as determined by DSC, WAXD, and FT-IR dat a. The critical length n for side-chain crystallization is a minimum o f 14 carbons, which is much larger than in the case of polyacrylates a nd polythiophenes, indicating the more rodlike character of polyanilin e backbones. In addition, with polymers of n greater than or equal to 16, a mesophase transition after melting of the side-chain crystallite s can be detected by optical microscopy and DSC.