Facile synthesis of carbon dioxide and UV light dual-responsive asymmetric tetrablock polymers

This work reports the synthesis of CO₂/ultraviolet (UV) light dual-responsive CABC-type asymmetric tetrablock polymers (CABC-ATP) based on organocatalyzed reversible complexation-mediated radical polymerization (RCMP) with methyl methacrylate (MMA), 2-Propenoic acid, 2-methyl-4-methyl-2-oxo-2H-1-benzopyran-7-yl ester (CMMA), and 2-(dimethylamino)ethyl methacrylate (DMAEMA) as block monomers by three steps. The obtained CABC-ATP has controllable number average molecular weight (M_n) and narrow molecular weight distribution (M_w/M_n = 1.18–1.29). The hydrodynamic diameter and fluorescence intensity were measured using dynamic light scattering coupled with fluorescence assays. Notably, the vesicle volume increased from an initial measurement of 247.6 nm to 285.4 nm post-experiment. The initial fluorescence emission intensity recorded was 4971, which decreased to 1412 following the introduction of carbon dioxide for 20 min. Subsequently, the fluorescence intensity recovered to 5199 upon nitrogen exposure. The response behavior of CABC-ATP to UV light is due to the cross-linking of coumarin-based monomer, resulting in the change of fluorescence intensity at the macro level. Besides, the protonation of tertiary amine is promoted by the stimulation of CO₂, generating of the change of vesicle volume at the micro level.