Accessing pluripotent materials through tempering of dynamic covalent polymer networks

Abstract

Pluripotency, which is defined as a system not fixed as to its developmental potentialities, is typically associated with biology and stem cells. Inspired by this concept, we report synthetic polymers that act as a single “pluripotent” feedstock and can be differentiated into a range of materials that exhibit different mechanical properties, from hard and brittle to soft and extensible. To achieve this, we have exploited dynamic covalent networks that contain labile, dynamic thia-Michael bonds, whose extent of bonding can be thermally modulated and retained through tempering, akin to the process used in metallurgy. In addition, we show that the shape memory behavior of these materials can be tailored through tempering and that these materials can be patterned to spatially control mechanical properties.

Editor’s summary

Tempering through controlled heating and cooling cycles is used to adjust the microstructure of a range of materials, including many metals and even chocolate. Boynton et al . extended this idea to reversible transformations of the mechanical properties in a single polymer system (see the Perspective by McAllister and Kalow). This method was achieved through the inclusion of thia-Michael bonds that are relatively weak and capable of reshuffling at lower temperatures compared with the covalent bonds in the polymer. At higher tempering temperatures, the cross-link density of the thia-Michael network decreases, resulting in a lower stiffness of the material, whereas tempering at lower temperatures creates a stiffer material. The material exhibits shape memory properties attributed to the dynamic reaction–induced phase separation caused by the change in bound and unbound cross-links. —Marc S. Lavine

Abstract

Dynamic networks can be differentiated through tempering into a range of materials with distinct mechanical properties.