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Carnegie Mellon scientists use 'green' approach to transform plastics manufacturing

d because ATRP previously required a high concentration of copper catalyst that had to be removed from finished products.

"Our new ATRP processes significantly reduce the cost of recycling the catalyst and also decrease the release of hazardous reaction byproducts found in industrial waste," Matyjaszewski added.

During ATRP, scientists produce a complex polymer structure using a special catalyst to add one or a few monomer units at a time to a growing polymer chain. ATRP requires a balance between two species of copper (Cu) catalyst, CuI and CuII. But as an ATRP reaction progresses, CuII builds up. Typically, researchers add more CuI to compensate for this effect and maintain the balance between the two copper species. But this approach ultimately generates materials with high overall levels of copper -- levels that are too costly to remove efficiently on a large-scale industrial basis.

The PNAS report highlights the team's novel use of "excess reducing agents" to lower the amount of copper catalyst from 5,000 parts per million (ppm) to 10 ppm. The team showed that you can steadily add environmentally benign "reducing" agents -- vitamin C, sugars or standard free radicals -- to chemically reduce CuII to CuI. This unprecedented approach continuously reduces CuII to CuI at the same rate CuII forms while retaining the desired balance between the two states. Ultimately, this technique dramatically lowers the overall amount of Cu catalyst used in ATRP by as much as 1,000 times.

The team's new technology virtually eliminates the need to remove miniscule amounts of catalyst remaining in a product. For example, many ATRP-generated plastics for medical implants would be acceptable from a health perspective because they contain so little copper. However, if the target application -- such as a coating for a biomedical stent -- absolutely requires the removal of residual catalyst, companies will now have much less of it to take out, signific
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Source:Carnegie Mellon University


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