On like a light

摘要

Control over the length and composition of polymers is key to controlling their properties. Now, a photoswitchable catalyst is shown to allow external control over reaction rates, chain lengths and even polymer composition in ringopening polymerizations. A precisely defined monomer sequence is essential for the function of biopolymers - such as DNA and proteins - in the control of a number of biological processes. The amino acid sequence in a protein, for example, determines its three-dimensional structure and small changes in the microstructure can affect both the final configuration and function. This concept can be also translated to synthetic polymers whose physical properties are altered by differences in chain length, tacticity and monomer sequence, among many other factors. The incredible advancements that have been made in living polymerization over the past two decades have enabled high levels of control over many of these parameters; however, controlling some of the more complex structural features - while retaining the attraction of working on a large scale - remains a significant synthetic challenge. Now, looking for alternative methodologies to achieve such complex structures, Stefan Hecht and co-workers1 report the use of a light-responsive catalyst to control ring-opening polymerization. This allows for additional regulation over a living polymerization and enables remote control of the macromolecular architecture of biodegradable polymers.