The earliest polymerizations of fluorene were oxidative polymerization with AlCl or FeCl, and more commonly electropolymerization. Electropolymerization is an easy route to obtain thin, insoluble conducting polymer films. However, this technique has a few disadvantages in that it does not provide controlled chain growth polymerizations, and processing and characterization are difficult as a result of its insolubility. Oxidative polymerization produces a similarly poor site-selectivity on the monomer for chain growth resulting in poor control over the regularity of the polymers structure. However, oxidative polymerization does produce soluble polymers (from side-chain containing monomers) which are more easily characterized with nuclear magnetic resonance.