A team at Cornell University has built a way to watch a polymer chain grow after the catalyst is applied. Writing in Science, the group describes how they did it — and their surprise at what they saw: the chains did not lengthen at a steady rate but in fits and starts, pausing and resuming.
The observation matters because models of polymerisation had assumed steady growth. Being able to see the process directly, rather than infer it from the properties of the finished material, changes what can be measured about it.