A team from the Olsen, Rubinstein, and Craig labs explore the question of reactivity-guided fracture in otherwise indistinguishable end-linked networks by tuning the relative composition of strands with two different mechanochemical reactivities. Increasing the substitution of less mechanochemically reactive (“strong”) strands into a network comprising more reactive (“weak”) strands has a negligible impact on the fracture energy until the strong strand content reaches approximately 45%, at which point the fracture energy sharply increases with strong strand content. Coarse-grained fracture simulations agree closely with the tearing energy trend observed experimentally, confirming that weak strand scissions dominate the failure until the strong strands approach percolation. Article Link

Professors Alshakim Nelson and Stephen Craig write the "Stimuli-responsive materials" section for the 2023 Soft Matter Roadmap. 'Stimuli-responsive' refers to materials that undergo a meaningful change in properties (the response) when subjected to a change in external environment (the stimulus). They discuss how various forms of energy and the introduction or removal of matter can in be coupled to an ever-increasing range of responses. Article Link

A team from the Steinmetz and Craig labs built an internal polymer “backbone” using a maleimide cross-linker to covalently interlink viral coat proteins inside the capsid cavity, while the native VLPs are held together by only noncovalent bonding between subunits. Endoskeleton-armored VLPs exhibited significantly improved thermal stability, increased resistance to denaturants, and enhanced mechanical performance. Article Link

The Kalow lab, in collaboration with the Air Force Research Laboratory, synthesized two oligosiloxane-based epoxy networks that provide fast dynamic bond exchange. The resulting polymer networks provided access to fast stress-relaxation times (1–10 min) at temperatures of only 130 °C with excellent reprocessability. This work provides a framework to utilize epoxy acids and siloxanes for dynamic materials, and the low viscosity of the siloxane monomers may offer further advantages for composite manufacturing processes. Article Link

A team from the Nelson and Craig labs demonstrate 3D printed, elastomeric ionogels comprising covalent adaptable networks (CANs) for modular sensor assemblies. The modular components can be combined and assembled on-demand into customized piezoionic sensors. This study highlights the benefits of dynamic covalent networks toward decentralized manufacturing, wherein a modular approach enables customization of 3D printed parts without the need for modifying the original design. Article Link

A team from the Schindler and Kulik labs report a visible-light-mediated approach that enables facile access to 1- and 2-azetine-based dimeric lactones of up to 30-membered ring macrocycles. This transformation occurs in one step and deviates from traditional macrolactonization methods. This new method may provide a unique avenue to access biologically interesting synthetic macrocycles. Article Link

A team from the Craig, Kulik, and Johnson labs report the mechanochemically coupled generation of hydrogen flouride (HF) from alkoxy-gem-difluorocyclopropane (gDFC) mechanophores derived from difluorocarbene addition to enol ethers. This latent source of HF resides within a polymer until released in response to a mechanical signal, at which point it be converted in situ to a flouride salt for use in self-immolative polymers, remodeled siloxane elastomers, vitrimer alteration, and degradable polymers. Article Link

The Center for the Chemistry of Molecularly Optimized Networks is officially open for business! Read one press release here .

MONET and Johnson lab trainee Yuwei Gu has received his PhD from MIT. Congratulations Dr. Gu!

Congratulations to Jeremiah Johnson, recipient of a 2019 ACS Cope Scholar Award ! Johnson was recognized “for developing methods for precision polymer synthesis that have generated macromolecules with novel functions and new insights into polymer network structure and mechanics.”

Congratulations to MONET team member Bradley Olsen on being named a Fellow of the American Chemical Society !

Congratulations to Rebekka Klausen, recipient of the 2021 ACS Award in Pure Chemistry ! Quoting Jillian Buriak (U. Alberta) in C&EN: “Professor Klausen’s work on polysilane chemistry is absolutely groundbreaking not only from a nanoscience viewpoint, but due to the smashing of preconceived notions of silicon chemistry, silicon can finally be viewed as much more than a poor relative of carbon in terms of synthetic chemistry. She has shaken up the world by showing that one can truly synthesize precise and controlled silicon-based molecules, and by extension, silicon nanomaterials.”