Multiresponsive Nonconjugated Polyelectrolyte Fluorescence Films

ABSTRACT

Fluorescent functional polyelectrolytes have been extensively applied in biomedicine and sensing technologies. Classic fluorescent conjugated polyelectrolytes involve complicated synthetic procedures. From a technological point of view, developing such materials via a straightforward synthetic route is desirable; however, attempts to achieve this have been largely unsuccessful. Herein, we introduce a new class of nonconjugated fluorescent polyelectrolytes (Poly(1,2,4‐triazolium)s, Ptriazs) that exhibit a broad fluorescence tuning range. This was achieved simply by changing the pendant groups attached to the cationic poly(1‐vinyl‐1,2,4‐triazolium) main chains. Experimental and theoretical studies revealed that the fluorescence modulation was achieved through‐space charge transfer driven by π–π, cation–π, and H‐bonding interactions. Notably, stable and uniform‐sized aqueous colloidal nanoparticles of Ptriazs can be readily made via precipitation polymerization method in water. We discover that bulk and nanoparticle Ptriaz films exhibit reversible excitation wavelength–dependent emission and water/temperature‐responsive fluorescence changes. These unique multiresponsive characteristics enable Ptiraz films to achieve multimodal optical encryption with security encoded by a myriad of external stimuli. These findings favor the scalable and rational development of nonconjugated fluorescent functional polyelectrolytes with strong potential for a wide range of applications.