High efficient mechanically induced atom transfer radical polymerization in aqueous media facilitated by piezoelectric heterostructures

Abstract

With ZnO/BaTiO₃ piezoelectric heterostructures as the catalyst, highly efficient ultrasonication-induced atom transfer radical polymerization (ATRP) in aqueous media was developed. Under ultrasonic action, the ZnO/BaTiO₃ heterostructure undergoes polarization and generates hole-electron pairs. The transfer of electrons to copper ions promotes the ATRP, while the strong oxidizing effect of the holes decomposes water molecules to generate hydroxyl radicals which lead to the loss of control of polymerization. By using ethanol as the co-solvent (V/V = 1/1) to capture the hydroxyl radicals and NaBr (0.66 mg/mL) to restrict the dissociation of bromide anions from the deactivator, the conversion of the monomer hydroxyethyl acrylate (HEA) reached 59.1 % within 12 min and 89.2 % within 30 min, in the presence of 600 ppm CuBr₂/tris(2-pyrodylmethyl) (TPMA) and 3 mg/mL ZnO/BaTiO₃ heterostructure, with low molecular weight distribution (M_w/M_n < 1.25). The polymerization can be temporally controlled by switching the ultrasound on and off, and it has also been demonstrated that the polymerization exhibits high chain-end fidelity. In addition, research was also conducted on the recycling of ZnO/BaTiO₃, and the results indicated that the polymerization catalytic system possesses characteristics of sustainable development.