Evaluation of suitable onium tetrafluoroborates for cationic polymerization of epoxides

Abstract

Epoxides are frequently used in coatings due to their great adhesion to most materials, high resistance towards chemicals and well-defined material properties. Onium salts such as iodonium and sulfonium salts are one of the most widespread classes of initiators used in light-induced cationic polymerization of such epoxides. We successfully synthesized onium salts based on group 14 to 16 elements in the periodic table. They were then characterized using cyclic voltammetry and UV-visible spectroscopy before determining their reactivity in epoxy-based resins. Using commercial bisphenol-A-based resins, thiopyrylium, bismuithonium and pyrylium salts show good reactivity and epoxy group conversions above 60% in simultaneous thermal analysis. Photochemically interesting new cationic initiators were identified to be oxonium, thiopyrylium and selenonium salts. Additionally, bismuthonium and stibonium salts show great potential towards sensitization with anthracene. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.