Orthogonal Relay Reactions for Designing Functionalized Soft Nanoparticles

The combination of reversible addition-fragmentation chain transfer (RAFT) chemistry followed by thiol-based click chemistry, known as an orthogonal relay reaction as one step complements the other, was used to produce surface-functionalized soft nanoparticles. Thiocarbonyl thio compounds were first used in the presence of vinyl monomers and a source of radicals to control the growth of the polymeric chains (via the RAFT process) and then reduced to thiols and utilized as a handle for functionalization of the resulting polymer chain ends (via a thiol-based click reaction). Both reactions occur under mild conditions and offer excellent control over the properties of the final product, and the thiol addition shows all the benefits of a click reaction, without requiring the use of a catalyst. This simple chemistry opens up the route to the production of a wide range of functional materials, and the concept is illustrated by the formation of nanoparticle-based gels, fluorescent-tagged particles, and protein-nanoparticle conjugates.