Ketenes in Polymer Science: An Emerging Methodology for Applications in Materials Chemistry

Function matters in materials science, and methodology that provides paths to multiple functions in one step are to be prized. Therefore, we have introduced the versatile reactivity of ketenes to polymer chemistry. New materials synthesized take advantage of Meldrum's acid as both a synthetic building block and a thermolytic precursor to dialkyl ketenes. In many cases, ketenes are directly detected by their characteristic infrared absorption, among other methods, and are stable in ambient conditions. The inherent property of ketenes to provide crosslinking via dimerization, to act as a reactive chemical handle via addition, or both, provides a simple methodology for the downstream engineering of synthetic polymers. The advances described herein provide a platform technology for diverse applications in materials science.;The key innovation to realizing access to robust ketenes was the use of Meldrum's acid as a modular, stable, and user-friendly ketene precursor that could be incorporated into a number of polymer systems. The easy design and synthesis of Meldrum's acid-containing polymers allowed us to implement this methodology into a wide variety of well-studied materials including vinyl polymers, polyolefins, polynorbornenes, and polyethers. The utility of ketenes has enabled them to contribute to a number of challenges in materials science, including the generation of functional, nanopatterned surfaces by microcontact printing, a synthesis-driven approach toward controlling the properties of crosslinked polyolefin materials, and the fabrication of mechanically robust, solvent stable nanostructured templates. Furthermore, we have tuned the chemistry of the Meldrum's acid building blocks in order to lower the ketene formation temperature by over 50 ºC, enabling our methodology to be employed under mild processing conditions and providing new mechanistic insights into thermolytic reactions.;The rediscovery of ketenes as a versatile and valuable functional group in polymer chemistry conjures the prolific career arc of Hermann Staudinger and serves as another example of under-appreciated functional groups contributing to polymer science. The facile access to Meldrum's acid containing polymers and the well-developed chemistry of ketenes assure that this methodology will be a powerful tool for chemists, materials scientists, and engineers in the future.