Seminar - SCM

Shape memory materials are smart materials that can reversibly switch between an equilibrium and a mechanically programmed state via an external trigger. While shape memory alloys (SMAs) were discovered first and continue to be widely used, this phenomenon is also exhibited by cross-linked polymers, which offer significant advantages over SMAs. Today, the field of shape memory polymers (SMPs) includes systems that deform reversibly with strains far beyond 100%, in response to heat, light, electrical, and chemical stimuli, thus offering a wide range of application areas. Conventional study and usage of SMPs involves deformation and “fixing” in the temporary shape by cooling induced crystallization/vitrification. In this work, we explore how the temporary state of the SMP reflects the history of imposed strain, stress, and temperature during the fixing protocol. We use a semi-crystalline shape memory polymer, crosslinked polycyclooctene (PCO), whose shape memory arises from network chain crystallization. We study how conditions during fixing affect the crystallization kinetics and outcome. Finally, by also varying the crosslink density, we establish how the crystallization kinetics affects the key features of shape memory in this polymeric system