Combination of phosphonium and ammonium pendant groups in cationic conjugated polyelectrolytes based on regioregular poly(3-hexylthiophene) polymer chains

A series of novel polythiophene-based cationic conjugated polyelectrolytes with phosphonium and ammonium pendants were prepared by modifying regioregular poly[3-(6-bromohexyl)thiophene] using a simple quaternization reaction with appropriate phosphine or amine. Partial transformation of the bromide end-groups of the polymer precursor with amine allowed adding the phosphine agent, thereby enabling quantitative transformation into a novel conjugated polyelectrolyte with phosphonium and ammonium groups in the same polymer main-chains. The properties of the synthesized polyelectrolytes in solution (water, methanol, DMSO and chloroform) were analyzed by UV/vis, luminescence, NMR, light scattering and TGA measurements. To test the prepared polyelectrolytes as potential luminescence sensors, fluorescence quenching measurements were performed in water, using K4[Fe(CN)6] and K3[Fe(CN)6] as quenchers. This study showed that polyelectrolytes containing both types of ionic pendant groups (phosphonium and ammonium) are more efficiently quenched.