Epoxy/Cystamine Vitrimer: Investigation of Shape Memory Behavior Along With Estimation of Topology Freezing Transition Temperature by Hardness Test

The epoxy/cystamine system has recently been introduced to polymer science as a novel vitrimer. This system can rearrange its topology through exchangeable disulfide bonds in the cystamine curing agent. Topology rearrangement occurs at temperatures higher than the topology freezing transition temperature and can exhibit unique properties like shape memory. Herein, performing hardness testing at different temperatures was provided as a novel and simple method to prove the existence of vitrimeric properties in the epoxy/cystamine network and to estimate the topology freezing transition temperature. According to the obtained results, the epoxy/cystamine system hardness values drop sharply in two temperature regions. The first region is in the temperature range of 40°C–60°C and is related to the glass transition temperature. In this region, the hardness decreases from 81 to 65 shore D. The second region occurs at temperatures above 80°C, where the hardness shifts to the shore A scale. This region can be related to the topology freezing transition temperature. At temperatures above 80°C, the epoxy/cystamine system behaves like rubber and can change shape. The shape memory behavior was quantitatively examined by the bending test. The results showed the shape retention ratio and shape recovery ratio for the epoxy/cystamine system are almost 100%. Moreover, the epoxy/cystamine system is a thermal‐sensitive shape memory polymer with fast and repeatable recovery. Furthermore, it has high durability over time and maintains its shape memory capability.