A Design of Transesterification Vitrimers with Variable Fractions of Network Defects and the Creep Characteristics

Abstract

AbstractVitrimer materials have attained great interest owing to their sustainable functions and distinctive physical properties. Compared with conventional cross‐linked materials, the thermoplastic‐like nature, such as the stress relaxation and creep at high temperatures, is outstanding, which is owing to the activation of the bond exchange in the cross‐linked network. The activation temperature of the bond exchange, so‐called topology freezing temperature (Tv), are treated as the important material parameters, and non‐isothermal (i.e., temperature‐ramp) creep test is one of the method to determine the Tv. This study investigates effects of network defects, that is, the breaking point of network connectivity, on the creep and Tv. The transesterification vitrimer samples with varying fraction of the network defects are designed using thiol‐epoxy click reaction, where the overall fraction of the bond exchange units, that is, the ester bond and hydroxyl group, is kept constant. Non‐isothermal creep tests are conducted with varying temperature‐ramp rate and applied stress levels, and the difference of Tv and creep behaviors at T > Tv are discussed in terms of network strand diffusion during bond exchange and chain elongation under stress.