Phloretic acid as an alternative to the phenolation of aliphatic hydroxyls for the elaboration of polybenzoxazine
Auteurs
A. Trejo-Machin, P. Verge, L. Puchot, and R. Quintana
Référence
Green Chemistry, vol. 19, no. 21, pp. 5065-5073, 2017
Description
3-(4-hydroxyphenyl)propanoic acid, so-called phloretic acid (PA), is a naturally occurring phenolic compound which can be produced from the hydrogenation of p-coumaric acid or synthesized from phloretin, a by-product of apple tree leaves. It was explored hereby as a renewable building block for enhancing the reactivity of –OH bearing molecules towards benzoxazine ring formation instead of phenol. PA was used to bring phenolic functionalities by reaction with model molecules (ethylene glycol, as well as two polyethylene glycol with molar masses corresponding to 400 g/mol and 2000 g/mol) via a solvent-free Fischer esterification. These phenolic groups were further reacted with a bio-based amine (furfurylamine) to form almost 100 % bio-based benzoxazine monomer end-capped molecules. Very interestingly, the whole synthesis of Bz monomers from PEG400 and PEG2000 did not require both solvent nor purification, and their polymerization led to a set of materials with thermal and thermo-mechanical properties suitable for a wide range of applications. These results show that renewable phloretic acid is a sustainable alternative to phenol to provide easily the specific properties of benzoxazine to –OH aliphatic bearing molecules or macromolecules. It paves the way towards a multitude of applications given the number of –OH bearing compounds in materials science.
