Advanced approach to O-alkyl/aryl salicylaldehyde derivatives: Synthesis, characterization, and free-radical homopolymerization for improved thermal stability

Abstract

In the development of bioactive materials centered around salicylaldehyde, we synthesized O-alkyl/aryl derivatives through the etherification of the phenolic group. Salicylaldehyde underwent a copper-catalyzed reaction with various halides under basic conditions, yielding 2-(3-chloropyrazin-2-yl)oxy benzaldehyde, 2-(6-chloropyrimidin-4-yl)oxy benzaldehyde, and 3-(2-formylphenoxy)-2-hydroxypropyl methacrylate. Meanwhile, 2-(2-formylphenoxy)ethyl methacrylate was synthesized via a sonication-assisted Mitsunobu reaction, affording high yields of ether derivatives. Structural elucidation was achieved using standard analytical techniques, such as ¹H NMR, ¹³C NMR, FT-IR and LC-MS. The free radical homopolymerization of 3-(2-formylphenoxy)-2-hydroxypropyl methacrylate using benzoyl peroxide as an initiator was successfully achieved. The resulting polymer exhibited enhanced thermal stability, as confirmed by solid-state ¹³C NMR, FT-IR, TGA, DSC, and SEM analyses, with a higher glass transition temperature than the reported poly(glycidyl methacrylate). This increase in T_g is attributed to the enhanced rigidity introduced by the aromatic ring in the homopolymer. This study highlights the successful synthesis of various O-alkyl/aryl salicylaldehyde derivatives using different techniques and functionalities, followed by the effective polymerization of one of the monomers, 3-(2-formylphenoxy)-2-hydroxypropyl methacrylate.