SuFEx-a selectively triggered chemistry for fast, efficient and equimolar polymer-polymer coupling reactions

The synergy between controlled radical polymerization methods and click chemistry enables the design of complex and well-defined materials. To date, a number of highly efficient reactions have been reported to be suitable to couple polymers in equimolar amounts within minutes, although such reactions typically require high reactivity, and the active groups are not fully compatible under the conditions applied in radical polymerization, necessitating additional modification steps. Here, we demonstrate how the Sulfur(vi) Fluoride Exchange (SuFEx) reaction proves to be an efficient coupling reaction whilst avoiding the traditional issues encountered in other ligation reactions. Two chain transfer agents (CTAs) for RAFT polymerizations were created, which bear the required orthogonal groups for the SuFEx reaction. Both CTAs yield well-defined polymers, with no observable side reactions, even when both CTAs are utilised in the same polymerization. The choice of the catalyst for this click reaction is an important consideration in order to allow efficient polymer coupling using equimolar amounts. Besides the previously reported strong bases, we discovered that the salt tetrabutylammonium fluoride (TBAF) is an excellent catalyst yielding almost quantitative conversions within minutes for different polymers and solvents. This combination of orthogonality towards radical processes and high reactivity is unprecedented in the literature.