By using resources and expertise at the Molecular Foundry, researchers from the Scripps Research Institute developed a new chemical process to create polymers containing sulfate or sulfonate. The new process is faster, easier, and cheaper than previous methods. The reaction will lower the cost of bringing these sulfur-containing materials — which could be used to make everything from water bottles and cell phone cases to medical devices and bullet proof glass — to large-scale production. The new process is known as sulfur(VI) fluoride exchange (SuFEx) reaction. Combined with a newly identified class of catalysts, the reaction can quickly make polysulfates and polysulfonates.
Polysulfonates and polysulfates have great potential in industrial and commercial plastic products However, they are rarely used. Why? Producing the materials requires large amounts of a highly corrosive catalyst. The catalyst, which drives the process, raised safety concerns and required extensive purification. The new technique dramatically increases product yield, requires 100 to 1,000 times less catalyst, and is far less hazardous. It opens the door to large-scale production.
Users from the Scripps Research Institute, including 2001 Nobel Prize laureate K. Barry Sharpless, teamed with scientists at the Molecular Foundry to characterize polymers generated during their search for a catalyst to efficiently create long chains of linked sulfate or sulfonate molecules, termed polysulfates and polysulfonates, using the SuFEx click reaction. While polysulfates have shown great potential as competitors to polycarbonates, they have been rarely used for industrial applications due to lack of reliable and easily scalable synthetic processes. The original process involved large amounts of highly corrosive catalyst, which required extensive purification and limited the types of starting materials that could be used.
To overcome the challenges inhibiting bulk synthesis of polysulfates and polysulfonates, the researchers explored various catalysts and starting reagents to optimize the SuFEx reaction. They relied on their collaborators at the Molecular Foundry to assess physical properties and determine if the newly created polymers were thermally stable products. The polymers are assembled from smaller molecules like stringing a repeating pattern of beads on a necklace. In creating a polysulfonate "necklace" with SuFEx, the researchers identified chemical compounds that would be good "beads" to use and found a bifluoride salt catalyst that made the previously slow reaction "click" into action. The high efficiency of the reaction results in a remarkable 99 percent conversion — from starting reactants to products in less than an hour. In addition, the new reaction produces less waste and allows for a wider range of starting "beads" results. All of these improvements make SuFEx more appealing for industrial processes.
Molecular Foundry, Lawrence Berkeley National Laboratory
Financial support for this work was provided by the National Science Foundation, the National Institutes of Health, the Chinese Natural Science Foundation, and the Major Research Project of Jiangsu Province Office of Education. Part of the work was carried out as a user project at the Molecular Foundry, which was supported by the Office of Science, Office of Basic Energy Sciences, U.S. Department of Energy.
H. Wang, F. Zhou, G. Ren, Q. Zheng, H. Chen, B. Gao, L. Klivansky, Y. Liu, B. Wu, Q. Xu, J. Lu, K.B. Sharpless, and P. Wu, "SuFEx-based polysulfonate formation from ethenesulfonyl fluoride–amine adducts." Angewandte Chemie International Edition 56, 11203-11208 (2017). [DOI: 10.1002/anie.201701160]
B. Gao, L. Zhang, Q. Zheng, F. Zhou, L.M. Klivansky, J. Lu, Y. Liu, J. Dong, P. Wu, and K.B. Sharpless, "Bifluoride-catalysed sulfur(VI) fluoride exchange reaction for the synthesis of polysulfates and polysulfonates." Nature Chemistry 9, 1083-1088 (2017). [DOI: 10.1038/nchem.2796]
Lawrence Berkeley National Laboratory news release: Making Polymer Chemistry "Click"