A new polymerisation process that requires less catalyst, occurs at room temperatures and allows chemists to use new monomers has been developed at the University of Pennsylvania (Philadelphia, Pennsylvania; USA; www.sas.upenn.edu/chem) by a team working under chemistry professor Virgil Percec claim to have created a new process for free radical polymerisation. "We have basically re-written the equation of how the polymerisation process can work," said Percec. This, he said, "can have a direct impact on the cost of the reaction and the types of materials that we can create."

The technique, called single electron transfer-living radical polymerisation (SET-LRP), is also claimed to offer chemists greater control over the molecular architecture of the polymers they create and allows them to use materials that do not work with the traditional process. The mechanism of the synthesis reaction is said to function so well that there is very little concern over undesirable side reactions, and the resulting polymers do not need to be purified to remove the catalyst. The findings were recently published in the "Journal of the American Chemical Society".

The new method involves the transfer of outer-sphere electrons, which requires much lower activation energy than required in the traditional process, and, therefore, a different catalytic cycle than atom-transfer radical addition.

Both the traditional and SET-LRP processes use copper-based catalysts to drive the reaction, but the SET-LRP reaction uses a common, elemental form of copper – in the form of powder or wire – in the presence of environmentally friendly solvents, such as water, to promote the reaction. This, the chemists claim, prevents the build-up of excess amounts of copper byproducts and reduces the need to continually add more catalyst to maintain the rate of reaction. The resulting polymers are structurally the same.