Glycerol Induced Catalyst‐Free Curing of Epoxy and Vitrimer Preparation

• Published in: Macromolecular rapid communications. Vol. 40; no. 7; pp. e1800889 - n/a
• Main Authors: Liu, Tuan, Zhang, Shuai, Hao, Cheng, Verdi, Christina, Liu, Wangcheng, Liu, Hang, Zhang, Jinwen
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.04.2019
• Subjects: Anhydrides; Anhydrides - chemistry; Carboxylic acids; Catalysis; Catalysts; catalyst‐free; coatings; Crosslinking; Curing; epoxy; Epoxy Compounds - chemistry; Glycerol; Glycerol - chemistry; Molecular Structure; self‐healing; Transesterification; Vitrimers; coatings; vitrimers; catalyst-free; epoxy; self-healing
• ISSN: 1022-1336; 1521-3927; 1521-3927
• DOI: 10.1002/marc.201800889

Epoxy vitrimers prepared from anhydride‐cured epoxies exhibit, repairable and reprocessable properties; however, they generally rely on a large amount of catalyst for accelerating the dynamic transesterification (DTER). If the catalyst loading is not enough, the vitrimer properties will be limited. In this work, a preparation method of catalyst‐free epoxy vitrimer is demonstrated by adding glycerol to an epoxy–anhydride curing system. The hydroxyls of glycerol first react with the anhydride to induce the ring‐opening of anhydride and form a carboxylic acid, and the latter attacks the epoxy and form a β‐hydroxyester linkage, so the curing can be performed in the absence of catalyst. A significant amount of hydroxy groups are preserved in the crosslinked network, and they serve as both reacting moiety and catalyst for the DTER, which imparts fast relaxation and satisfactory repairability to the materials. By taking advantage of this mechanism, a catalyst‐free and self‐healing coating is demonstrated. These findings provide a solution to avoid using catalyst in vitrimer preparation and advance the application of vitrimer in coating. However, the addition of glycerol produces a decrease of the T g of the final materials, which needs to be further addressed in the future study. A new preparation method of catalyst‐free epoxy vitrimer is developed by introducing glycerol to a commercial epoxy–anhydride curing system. Use of the resulting vitrimer for the repairable coatings is demonstrated. This method can be easily expanded to use of other polyhydric compounds as modifiers for preparation of catalyst‐free vitrimers.