CHAPTER 17: Self-Doped Polymers

Self-doped conducting polymers are conjugated polymers in which at least a fraction of monomer units contain covalently-attached ionizable functional groups that can act as immobile dopants. The synthesis of self-doped polymers is generally performed in two ways; by modifying the existing polymer structure (e.g., addition of ring or N-substituents) or polymerizing the corresponding monomers using either chemical or electrochemical methods. Additional polymerization techniques such as Suzuki coupling and Ring Opening Metathesis Polymerization (ROMP) can also be employed to synthesize several self-doped polymers. Although self-doped polymers can be synthesized directly by polymerizing the substituent monomers, often they do not polymerize alone due to their lower reactivity and steric effects. In such cases, the substituent monomers are typically copolymerized with their parent monomers. This chapter reports the synthesis and characterization of a number of self-doped polymers including sulfonic acid, carboxylic acid and phosphonic acid substituted polyanilines, polypyrroles and polythiophenes; substituted polycarbazoles, poly(p-phenylene)s, poly(phenylenevinylene)s, polyindoles and polyacetylenes. This chapter also reports important characterization techniques including elemental analysis, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), spectroelectrochemistry and electrochemical quartz crystal microbalance (EQCM) that are widely used to characterize the elemental composition, structural behavior and dopant level of self-doped polymers.