Mechanism model of dynamic polyurethanes with two scales of nodes to regulate mechanical property

Abstract

Dynamic polyurethanes break the boundaries between thermoplastics and thermosets; while realizing reprocessing, their strength is often weakened and uncontrollable, the processing methods are cumbersome and environmentally unfriendly. Herein, we report a molecular topological structure model of polyether-based dynamic polyurethanes with polyphenols for mechanical property regulation; taking pyrogallic acid, polyethylene glycol, and hexamethylene diisocyanate trimer as an example, the elastic modulus ranges from 162.38 to 1038.62 MPa, and the tensile strength ranges from 1.70 to 42.88 MPa,and the tensile elongation can reach up to 47.26 %. Distinctively, the relationship between molecular, microscopic, and macroscopic structure and mechanical properties is explained in terms of topological structure; no catalyst and solvent are employed during the simple and fast synthesis. The mechanical properties are regulated by changing the ratio of polyols as flexible long chains and the two-scale rigid joints composed of benzene rings and isocyanate-urea rings. They are mainly provided by hydrogen bonds and carbamate groups, the formation of which is affected by steric effects, hydroxyl reactivity, and hydrogen bonding. This provides reference for prepare polyurethane with better mechanical properties in dynamic polyurethane industrial products through molecular topological structure design using same type of raw materials.

Keywords

• Dynamic polymer
• Polyurethane
• Mechanical properties regulation
• Reaction mechanism
• Molecular model