Oxime-Based and Catalyst-Free Dynamic Covalent Polyurethanes

• DOI: 10.1021/jacs.7b03967
• Publication Date: 2017-05-30T18:23:04Z
• Authors: Wen-Xing Liu; Chi Zhang; Huan Zhang; Ning Zhao; Zhi-Xiang Yu; Jian Xu
• Keywords: Hexamethylene diisocyanate; Carbamate

Polyurethanes (PUs) have many applications resulting from their preeminent properties, but being commonly used toxic catalysts, and the lack of processability for PU thermosets cause limitations. Herein, we report a new class PU-like dynamic covalent polymers, poly(oxime-urethanes) (POUs), which are prepared uncatalyzed polyaddition multifunctional oximes hexamethylene diisocyanate (HDI) at ambient temperature. Kinetics studies reveal that almost complete polymerization (∼99% conversion) can be achieved in 3 h 30 °C dichloromethane (DCM), most effective among solvents evaluated, producing linear POUs with comparable molecular weights to catalyzed PUs. We find oxime-carbamate structures reversible about 100 through oxime-enabled transcarbamoylation via thermally dissociative mechanism. The cross-linked based on bonds show efficient catalyst-free healable/recyclable properties. Density functional theory (DFT) calculations suggest fast oxime-urethanation mild thermoreversible nature mediated by characteristic nitrone tautomer oxime. Given widespread urethane-containing materials, promising potential because excellent mechanical performances, facile preparation, property without using catalysts.