# Fully Biobased Epoxy–Imine Monomer: Synthesis and Curing with Amines Toward Vitrimeric Materials

## TL;DR

Scientists created a fully biobased epoxy monomer that can be used to make recyclable materials with potential applications in adhesives and composites.

## Contribution

A new fully biobased epoxy–imine monomer was synthesized and shown to enable vitrimeric materials with reprocessing and recycling capabilities.

## Key findings

- The epoxy monomer can be melted at 100°C without solvents, facilitating formulation with curing agents.
- Materials made with the monomer exhibit vitrimeric behavior, allowing chemical and mechanical recycling.
- The monomer is a promising alternative to DGEBA in thermosetting applications.

## Abstract

This study presents the synthesis of a new biobased epoxy
monomer
derived exclusively from biobased vanillin and epichlorohydrin. Using
only sustainable processes, vanillin is first converted to vanillin
amine hydrochloride, which is then condensed with vanillin to obtain
a diphenol containing an imine moiety. This diphenol subsequently
reacts with epichlorohydrin to produce the epoxy monomer. Unlike thermosetting
networks in which the imine is formed during the curing reaction,
this epoxy monomer incorporates the imine moiety, and no further processing
is needed after network formation due to water release. It presents
a low molecular weight (399.44 g/mol), enabling the formation of a
wide range of highly cross-linked materials. The epoxy monomer can
be melted at 100 °C, which facilitates its formulation with the
curing agents without the need for solvents. The monomer was cured
in this work with two diamines, isophorone diamine (IPDA), a commonly
used curing agent, and cystamine (Cyst) as a biobased amine that contains
a dynamic disulfide group, to obtain a 100% biobased material. The
resulting materials were compared with DGEBA/IPDA and DGEBA/Cyst formulations
in terms of thermomechanical properties to evaluate whether the new
monomer could be a promising alternative to DGEBA. No less important
is the fact that the presence of the imine moiety in the monomer gives
vitrimeric behavior to the material. This feature enables reprocessing
of the material and allows for both chemical and mechanical recycling.
Such properties are particularly promising for applications such as
reversible adhesives or degradable matrices in composite materials.