Deep focusing on the role of microstructures in shape memory properties of polymer composites: A critical review

In the last two decades, shape memory polymers (SMPs) find promising applications in various fields such as micro-actuators, medicine, basic sciences, anti-counterfeit technology, sensor, and automobile. This class of active polymers can switch between an original shape and one or more temporary shapes. Although SMPs have been extensively admitted as smart materials, due to low density, excellent biocompatibility, and facile processing, but still exposes numerous weaknesses and limitations based on engineering aspects, analogous: multiple approaches to improvement of driving methods, reinforcement of mechanical properties, the creation of specific deformations and the formation of multifunctional materials. For this purpose, SMP composites (SMPCs) is introduced to eliminating the mentioned disadvantages. This review is intensely focused on the most recent research on microstructure-property of SMPCs filled by different carbon and silicate-based nano/micro-particles as well as hybrid particles. Silicate fillers in SMPCs divided base on natural shapes (1, 2 and 0 D) and the necessary information for tailoring an appropriate SMPCs is deliberated. On the other hand, the embedded carbonic fillers (carbon black, CNT and graphene) in polymeric matrixes for improving shape memory behavior are separately deliberated. In addition, the current review offers a comprehensive discussion on micro- and macro-morphology of polymer composites in order to design proper shape memory properties. A systematic approach has been undertaken to highlight the advancements and challenges of SMPCs and the critical research areas that need immediate attention.