Optical properties of phosphonium-, quaternary ammonium- and imidazolium- substituted regioregular polythiophenes and application for imaging live cells

Cationic side chains on conjugated polyelectrolytes play crucial roles in the state of polymer chains in water as well as the interactions with live cells. However, it is difficult to compare the effect of different cationic side chains due to the structural defect and severe aggregation issue. We synthesized structurally defined cationic polythiophenes with pendent phosphonium-, quaternary ammonium- and imidazolium-substituted side chains, and confirmed molecularly dispersed state of them in aqueous solutions by spectroscopic characterizations. We also investigated the cytotoxicity as well as cell binding and intracellular trafficking by imaging live cells in the absence and presence of hyaluronic acid.