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Shape memory polymer (SMP) is a kind of smart material that can fix temporary shape under certain conditions and can restore to its original shape under external stimulus. It is used in flexible electronic devices, biomedicine, aerospace and other fields. widely. Thermoset shape memory polymers, as an important component of shape memory polymers, have superior stability and shape memory properties compared to thermoplastic shape memory polymers. However, once the thermosetting polymer is cross-linked and cured, its shape cannot be changed, that is, the original deformation of the shape-memory polymer can no longer be changed, thereby limiting its application.
The team led by Wang Qihua, a researcher at the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, introduced a dynamic covalent adaptable network (CAN) into thermoset polymers to achieve the original shape reconstruction of thermoset shape memory epoxy resins. The dynamic covalent bond adaptive network structure is capable of covalent bond exchange reactions under certain heat or light stimulation, and thus can achieve properties such as welding and reprocessing of thermosetting polymers.
The researchers introduced temperature-induced dynamic covalent bonds with transesterification properties in the epoxy resin, changed properties at the transesterification temperature for a certain period of time, and then achieved complete relaxation of stress via dynamic transesterification, resulting in new shape. Both qualitative and quantitative characterizations show that both the original trait and the reconstructed shape have excellent shape memory performance. In addition, due to the brittleness of the epoxy resin, the mechanical properties of the epoxy are greatly improved by the introduction of the enhanced graphene, which provides a guarantee for obtaining a large deformation of the shape memory and the reconstruction performance. At the same time, graphene, as a good light-to-heat conversion material, can convert infrared light into heat energy, thus achieving infrared light-induced shape recovery.
The preparation of the shape reconfigurable shape memory polymer is expected to provide new ideas for the reprocessing, self-healing and shape reconstruction of the thermoset shape memory polymer, and also broaden the application range of the thermosetting shape memory polymer material.
The above work has been funded by the national key basic research and development program ("973" program), the National Defense Innovation Fund of the Chinese Academy of Sciences and the National Natural Science Foundation. The related results were published in the American Chemical Society's Applied Materials and Interfaces (ACS applied materials & interfaces 2016, 8 (33), 21691-21699).
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