The ability to reverse
controlled radical polymerization and regenerate
the monomer would be highly beneficial for both fundamental research
and applications, yet this has remained very challenging to achieve.
Herein, we report a near-quantitative (up to 92%) and catalyst-free
depolymerization of various linear, bulky, cross-linked, and functional
polymethacrylates made by reversible addition–fragmentation
chain-transfer (RAFT) polymerization. Key to our approach is to exploit
the high end-group fidelity of RAFT polymers to generate chain-end
radicals at 120 °C. These radicals trigger a rapid unzipping
of both conventional (e.g., poly(methyl methacrylate)) and bulky (e.g.,
poly(oligo(ethylene glycol) methyl ether methacrylate)) polymers.
Importantly, the depolymerization product can be utilized to either
reconstruct the linear polymer or create an entirely new insoluble
gel that can also be subjected to depolymerization. This work expands
the potential of polymers made by controlled radical polymerization,
pushes the boundaries of depolymerization, offers intriguing mechanistic
aspects, and enables new applications.
The calculation of accurate reaction energies and barrier heights is essential in computational studies of reaction mechanisms and thermochemistry. To assess methods regarding their ability to predict these two properties, high-quality benchmark sets are required that comprise a reasonably large and diverse set of organic reactions. Due to the time-consuming nature of both locating transition states and computing accurate reference energies for reactions involving large molecules, previous benchmark sets have been limited in scope, the number of reactions considered, and the size of the reactant and product molecules. Recent advances in coupled-cluster theory, in particular local correlation methods like DLPNO-CCSD(T), now allow the calculation of reaction energies and barrier heights for relatively large systems. In this work, we present a comprehensive and diverse benchmark set of barrier heights and reaction energies based on DLPNO-CCSD(T)/CBS called BH9. BH9 comprises 449 chemical reactions belonging to nine types common in organic chemistry and biochemistry. We examine the accuracy of DLPNO-CCSD(T) vis-a-vis canonical CCSD(T) for a subset of BH9 and conclude that, although there is a penalty in using the DLPNO approximation, the reference data are accurate enough to serve as a benchmark for density functional theory (DFT) methods. We then present two applications of the BH9 set. First, we examine the performance of several density functional approximations commonly used in thermochemical and mechanistic studies. Second, we assess our basis set incompleteness potentials regarding their ability to mitigate basis set incompleteness errors. The number of data points, the diversity of the reactions considered, and the relatively large size of the reactant molecules make BH9 the most comprehensive thermochemical benchmark set to date and a useful tool for the development and assessment of computational methods.
Diazirine reagents allow for the ready generation of carbenes upon photochemical, thermal, or electrical stimulation. Because carbenes formed in this way can undergo rapid insertion into any nearby C–H, O–H...
Motivated by a desire to develop flexible covalent adhesives that afford some of the same malleability in the adhesive layer as traditional polymer-based adhesives, we designed and synthesized two flexible,...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.