Synthetic Metals

Growth instability in diffusion controlled polymerization

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We report the observation of a sharp transition in the structure of polypyrrole prepared via diffusion controlled polymerization in a quasi-two dimensional electrochemical cell. As the oxidation potential is increased, the fractal dimension drops sharply from values near 2 to 1 as the growth becomes dendritic. At higher potentials, where the polymerization becomes diffusion limited, a continuum of structure is observed as the dendrites become more irregular and the fractal dimension increases to 1.74±0.01. © 1987.