An overview of epoxy vitrimers

R. J. J. WILLIAMS

Tarragona

Simposio; VII International Baekeland Symposium; 2019

Universidad Rovira i Virgil

Since the seminal papers of Leibler?s group [1-3], the field of epoxy vitrimers has expanded at a high rate. These materials are synthesized by the crosslinking of epoxy monomers employing carboxylic acids or carboxylic anhydrides. They exhibit the typical behaviour of thermosetting polymers below their glass transition temperatures but undergo flow at high temperatures due to the exchange of covalent bonds produced by transesterification reactions. This enables their recycling, self-healing, shape reconfiguration and a set of other properties that constitute the driving force for the present search of industrial applications.Materials synthesized by the reaction of epoxy monomers with carboxylic acids will be first analyzed. Several important issues related to the effect of transesterification reactions on the network structure will be analyzed [4]. The meaning (if any) of the so-called topological freezing transition temperature will be discussed. The effect of usual transesterification catalysts (Zn+2 salts or tertiary amines) will be compared to the possibility of formulating materials without catalysts [5] or using non-conventional catalysts covalently bonded to the polymer structure [6]. Selected papers from the recent literature will be discussed showing ways to adapt this chemistry to provide vitrimer properties to conventional rubbers, silica-modified epoxies and other materials, Examples of formulations providing very fast relaxation rates or enabling remote activation of transesterification reactions will be presented.Finally vitrimers produced by the crosslinking of epoxy monomers with carboxylic anhydrides will be analyzed focusing on reactions generating the hydroxyl groups needed for transesterification reactions.