Fully bio-based acetal diepoxy monomer with high modulus, good thermal stability and readily degradability†

Abstract

Degradable epoxy resins are designed to address the environmental pollution caused by traditional epoxy resins. However, incorporating the degradability of dynamic covalent bonds in the design of degradable resins often compromises the rigidity and heat resistance of the material, rendering it less suitable for high-temperature applications, such as those used in deep space exploration. This paper presents the creation of an innovative, entirely bio-based epoxy monomer. Its cyclic rigid dynamic bonds confer a high tensile modulus (4.06 GPa), glass transition temperature (T_g = 240 °C), notable creep resistance with full shape recovery at 180 °C, and remarkable degradability, dissolving entirely in a 1 M HCl solution in just 60 minutes at 50 °C. The preparation of the diacetal was accomplished by reacting vanillin with xylitol under acidic conditions. This was followed by a reaction with bio-derived epichlorohydrin to produce bio-based, multifunctional epoxy monomers featuring hydroxyl groups and bicyclic acetal structures, representing a new strategy for eco-friendly polymer synthesis. This monomer was then cured with a hardener to create an epoxy crosslinked network. The eco-friendly raw materials are easily obtainable, and the synthesized cross-linked network structure is exceptionally high-performing. This makes it a potential material for use in deep space exploration and other tough environments, and it provides a benchmark for synthesizing chemically degradable epoxy resins suitable for extreme conditions.