Research Progress of Shape Memory Polymer Deformation Mode

Abstract

Shape memory polymers are the most widely studied smart deformable materials at present. Due to their low density, large deformation, high stress resistance, various driving methods, good biocompatibility, easier modification and processing, shape memory polymers have become a cutting-edge research in the field of smart materials. Under certain external stimulus (such as temperature, light, electric field, magnetic field, pH, specific ions, enzymes, etc.), shape memory polymers can change their shapes according to pre-designed way and quickly change from temporary shape to permanent shape. Shape memory polymers have shown great application potential in aerospace, biomedicine, bionic engineering, electronic devices, intelligent robots and other fields, which effectively overcome the bottleneck problems in the corresponding fields. In order to make the shape memory polymers more suitable for various fields, not only a simple deformation process from a temporary shape to a permanent shape is needed, the deformation mode should also be improved to adapt the actual situation in practical applications. In this paper, the deformation modes of shape memory polymers are divided into four categories, including the simple dual shape memory deformation mode, the multiple shape memory deformation mode with multiple temporary shapes, the self-folding deformation mode, and the reversible two-way shape memory deformation mode. Multiple shape memory polymers generally have multiple reversible switches or a wide range of temperature switches, which have greater freedom in practical applications. The self-folding structure can spontaneously fold/unfold to the desired shape under stimulation conditions without artificially giving shape, so it has great application prospects in the fields of space systems and self-assembly systems. The reversible shape memory polymer can reversibly convert between permanent and temporary shapes under stimulation conditions, which show great application prospects in the fields of sensors and drivers. The deformation modes are more diversified which can fulfill different requirements in various applications. The deformation mode is an important functional index of shape memory materials. Therefore, from the perspective of different deformation modes of shape memory polymers, this paper reviews the different deformation modes of shape memory polymers and the progress of their related applications, as well as the challenges faced by different deformation modes and their potential research directions.