Synthesis of Electron-Deficient Borinic Acid Polymers with Multiresponsive Properties and Their Application in the Fluorescence Detection of Alizarin Red S and Electron-Rich 8-Hydroxyquinoline and Fluoride Ion: Substituent Effects

Electron-deficient borinic acid monomers and corresponding polymers were synthesized with different substituents via a one-pot reaction of Grignard reagents with trimethoxyborane and reversible addition fragmentation chain transfer polymerization, respectively. Further investigations of substituent effects of borinic acid polymers (PBAs) were carried out, indicating that the thermoresponsive properties of PBAs benefit from the increase of steric hindrance of PBA substituent, while the binding affinity of PBAs with Alizarin Red S, 8-hydroxyquinoline (HQ), and fluoride ion decreases with the increase of steric hindrance of substituent. Attributed to the strong dative N -> B bond and the strongly luminescent boron quinolate, the application of phenyl PBA for fluorescence detection of HQ is realized with high sensitivity at the ppm level. These results therefore confirm that borinic acid containing polymer is a new type of stimuli-responsive polymer in the field of thermoresponsiveness over a wide temperature range and chemical sensor for diol and electron-rich compounds.