Multi-stimuli responsive and intrinsically luminescent polymer metallogel through ring opening copolymerization coupled with thiol-ene click chemistry

Luminescent polymer based metallogels have gained considerable interest due to their wide range of applications in the fields of drug delivery, tissue engineering, sensing, and optical systems. One of the challenges in the area is to tune the properties of metallogels for a given application, which is largely controlled by the choice of the functional groups in the polymer and the binding metal ions. In the present study, efforts are made to utilize ring opening copolymerization followed by functionalization by thiol-ene click chemistry to attach desirable functional groups to the polymer for preparing polymer based metallogels. A norbornene-alt-cyclohexene oxide based polymer is synthesized to develop an intrinsically luminescent metallogel using lanthanide metal-ligand complexation. The optical properties of the polymer metallogel are modulated via a dual channel process where a cluster induced intrinsic emission surpasses resonance energy transfer mechanism, leading to cool white light emission from the metallogel [CIE coordinates (0.33, 0.37);correlated color temperature 5752 K], with reversible vapochromism and irreversible chemochromism. Our studies suggest that the combination of ring opening co-polymerization and thiol-ene click chemistry is a potential design strategy for preparing polymer based metallogels with multi-stimuli responsive properties.