Structure and properties of a flame retardant ternary vitrimer regulated by cyclic and long-chain dicarboxylic acids

A vitrimer is a kind of polymer with a dynamic network that has received extensive attention. An epoxy monomer containing a phosphonate group (E) has been used to endow a vitrimer with flame retardancy. 1, 4-cyclohexanedicarboxylic acid (CA) was used as a diacid monomer. Dodecanedioic acid (DA) containing a long aliphatic chain was used as a third monomer to regulate the structure and properties of the vitrimer. The flame retardant properties were investigated using UL-94 vertical combustion, limiting oxygen index (LOI). The results showed that the E/1C/2D vitrimer containing CA/DA (mole ratio1:2) displays a UL-94 V-0 rating and a LOI value of 31%. Furthermore, the vitrimers possesse excellent recyclable and multiple shape memory performance. The E/1C/2D vitrimer may be structurally modified rapidly via transesterification reaction between an ester and neighboring β‑hydroxy groups at 170 °C. The recycling efficiency is nearly 100%. The tensile strength and modulus of E/1C/2D may be as high as 97 MPa and 2173 MPa, respectively. The tensile strength is not significantly decreased as a consequence of two reformation events. A simple method for the regulation of the flame retardancy and mechanical properties of vitrimers has been demonstrated.