The 2023 in-person meeting before the ACS Spring Meeting in New Orleans. A day of talking science and exploring new directions in Broader Impacts!

A team from the Johnson lab and others at MIT collaborated with Université Paris-Saclay to propose a model where the relaxation of polymer gels in the dilute regime originates from elementary events in which the bonds connecting two neighboring cross-linkers all disconnect. The approach is simple enough to be extended to any cross-linker size and could thus be harnessed for the rational design of complex viscoelastic materials. Article Link

Klausen lab postdoc Kelsie Wentz was named a Future Faculty Scholar by the ACS Division of Polymeric Materials: Science and Engineering (PMSE). Kelsie will provide a technical talk at the ACS Fall Meeting in Denver, and participate in a networking reception with other Future Faculty Scholars, keynote speakers, and selected invited guests from academia and other sectors.

A team from the Johnson and Kulik labs introduce the concept of leveraging “nested” supramolecular crosslinks to control bulk material functions. In these nested crosslinks two distinct supramolecular interactions exist in parallel and influence each other. In the future, this may leverage the vast existing body of known MOC host-guest binding properties to accelerate the creation of soft materials with exquisitely selective small-molecule-driven property changes for applications ranging from sensing to biomaterials. Article Link

A team from the Kalow and Kulik labs report the use of bifunctional aromatic thioesters as dynamic covalent cross-links in hydrogels, demonstrating that at physiologic pH in aqueous conditions, transthioesterification facilitates stress relaxation on the time scale of hundreds of seconds. This system exemplifies how dynamic cross-links that exchange through an associative mechanism enable tunable stress relaxation without altering stiffness. Article Link

A team from the Gong and Craig labs embedded cyclobutane-based mechanophore crosslinkers in the first network of double network hydrogels and achieved efficient activation with 100% selectivity.  These findings provide crucial design principles for achieving selective mechanophore activation and deepen our understanding of the damage mechanism within polymer networks when utilizing mechanophores as detectors. Article Link

A team from the Campos, Nelson, and Rubinstein labs report the use of carbazole-based thiuram disulfides (CTDs) that offer dual reactivity as photoactivated reshuffling linkages and iniferters under visible light irradiation. The fast response to visible light activation of the CTDs leads to temporal control of shape manipulation, healing, and chain extension in the polymer networks, despite the lack of optical transparency. Article Link

A team from the Moore, Craig, and Kulik labs detail a non-scissile mechanophore built from an 8-thiabicyclo[3.2.1]octane 8,8-dioxide (TBO) motif that releases one equivalent of sulfur dioxide (SO2) from each repeat unit. These comprehensive studies of TBO mechanophore provide a mechanically coupled mechanism of multi-SO2 release from one polymer chain, facilitating the translation of polymer mechanochemistry to potential biomedical applications. Article Link

A team from the Klausen, Craig, and Kulik labs report the synthesis of two new examples of 7- and 8-membered sila-cycloalkynes, as well as an investigation of their strain-promoted reactivity with azides. The results demonstrate that measurable angle-strain alone is insufficient for room-temperature cycloaddition, influencing design principles in an area broadly relevant to organic chemists and chemical biologists. Article Link

In this article, researchers from the Klausen, Kulik, Moore, Kalow, Sottos, and Johnson labs highlight the use of a comonomer strategy for silyl ether exchange yielding deconstruction and bulk remolding in pDCPD thermosets. Article Link

In this Perspective, researchers from the Sottos and Craig labs speculate as to the potential match between covalent polymer mechanochemistry and recent advances in polymer network chemistry, specifically, topologically controlled networks and the hierarchical material responses enabled by multi-network architectures and mechanically interlocked polymers. Article Link

The Sottos, Johnson, and Moore labs demonstrate end-of-life deconstruction and upcycling of high-performance poly(dicyclopentadiene) (pDCPD) thermosets with a concurrent reduction in the energy demand for curing via frontal copolymerization. Article Link