AIE-Active Random Conjugated Copolymers Synthesized by ADMET Polymerization as a Fluorescent Probe Specific for Palladium Detection

Using acyclic diene metathesis (ADMET) polymerization, we have synthesized a series of random conjugated copolymers from diene monomers based on tetraphenylethene (TPE), which is an aggregation-induced emission (AIE)-active molecule, and comonomers such as 1,9-decadiene, 2,7-divinyl-9,9-di-n-octylfluorene, and 1,4-dihexyl-2,5-divinylbenzene. These all-hydrocarbon copolymers exhibit good solubility and high molecular weights. As proved by H NMR spectra, chain segments composed of two monomers are randomly distributed in the polymers. Absorption and emission features from both TPE units and those conventional diene segments in conjugated copolymers are observed in their optical spectra. Because of the presence of AIE-active TPE units, emission intensities of the copolymers are greatly enhanced in tetrahydrofuran/water mixtures with increased water content. Moreover, the fluorescence of ADMET polymers can be quenched by palladium ions in quasi-aqueous solutions following a dynamic quenching mechanism. The fluorescence quench degrees are affected by both chemical structures of the copolymers and the solvent polarity. Our findings demonstrate that ADMET conjugated polymers have enormous potential as fluorescent "turn-off" probes specific for palladium ions even in the absence of a particular coordination interaction.