Fluorescent copolymer aggregate sensor for lithium chloride

We report a copolymeric fluorescent sensor that is selective for lithium chloride. The two constituent polymers comprise pendent triphenylethylene (TPE) moieties for aggregate induced emission (AIE) along with either strapped-calix[4]pyrrole or secondary ammonium groups that drive aggregation via self-assembly upon polymer mixing. Addition of LiCl in acetonitrile disrupts the strapped-calix[4]pyrrole/secondary ammonium chloride salt host-guest crosslinks leading to disaggregation of the polymer chains and a decrease in TPE emission. The lack of AIE perturbation upon addition of NaCl, KCl, MgCl₂ or CaCl₂ provides for high selectivity for LiCl relative to potential interferants. This supramolecular dual polymer approach could serve as a complement to more traditional sensor systems.