Water-Soluble Multifunctional Cross-Conjugated Poly(<i>p</i>-phenylenes) as Stimuli-Responsive Materials:  Design, Synthesis, and Characterization

Abstract

The design, synthesis, and characterization of a series of thermally stable water-soluble polymers with cross-conjugation and multiple functional groups are reported. All copolymers were characterized by means of FT-IR, GPC, 1H and 13C NMR, UV−vis, and fluorescence spectroscopy. Photophysical properties showed collective responses from their respective conjugated segments. Titration studies showed that such polymers have good sensitivity for both cationic and anionic quenchers in fluorescence decay, with an average Stern−Volmer constant of 105 M-1. Besides fluorescence quenching, significant shifts in absorption and emission maxima upon addition of small molecules were also observed. High concentration of small molecular quenchers induced aggregation of the polymers. All polymers were able to form highly fluorescent, flexible, free-standing thin films via evaporation of the solvent. Hence, by attaching cationic and anionic groups on a cross-conjugated water-soluble structure, a multifunctional CP system was developed for potential applications