Supramolecular grafting of doped polyaniline leads to an unprecedented solubility enhancement, radical cation stabilization, and morphology transformation

Abstract

We have demonstrated an entirely supramolecular approach for polymer grafting where polyaniline (PANI) is grafted with polyethylene glycol (PEG) coupled with β-cyclodextrin forming a pseudorotaxane with the aniline moiety. The resultant supramolecularly grafted PANI (βCD-PEG-PANI) in the doped state shows an extremely high solubility towards aqueous as well as organic solvents. Furthermore, the grafted PANI exhibits a higher degree of doping and a highly efficient radical cation stabilization, compared to a control PANI system synthesized under identical conditions. The redox switching behavior of PANI is also fully retained in βCD-PEG-PANI. An unusual disk-like morphology has been observed in βCD-PEG-PANI irrespective of the nature of the solvent. The pseudo-micellar assembly formation of βCD-PEG-PANI has been attributed to the high solubility, efficient radical cation stabilization, and unconventional morphological behavior of the grafted PANI. The present system represents a powerful integration of three key elements: first, fascinating electronic and physicochemical properties of parent PANI; second, extremely high aqueous solubility; and third, biocompatibility transcribed from PEG and βCD. While the first two characteristics are highly beneficial for technology generation, a combination of all three can open up a new era for biocommunication systems. The non-specific mode of interactions between the monomer (aniline in this case) and βCD-PEG implies that such a supramolecular strategy can be employed for a wide range of polymers including other conducting polymers.