Molecular recognition effects in polyaniline

Polyaniline (PANI) is known to dissolve in strong acids, such as sulphonic acids. PANI, in its electrically conductive form, is generally regarded to be poorly soluble in low-acidic solvents and to be infusible, closely resembling fully aromatic rigid rod polymers. We show that “less” acidic solvents and plasticizers can be found based on phenyl-phenyl interactions in combination with hydrogen bonding. The requirement is that the interactions are strong enough and, importantly, sterically match the complementary moieties of the sulphonic acid doped PANI. Dihydroxybenzenes and bisphenols are examples of such low-acidic compounds. This type of molecular recognition allows solution and melt processibility of PANI doped by generic sulphonic acid, such as methanesulphonic acid or alkylbenzenesulphonic acid. Molecular recognition is also offered as an explanation for the previously observed high solubility of camphorsulphonic acid (CSA) doped PANI in phenols.