Low-Temperature Cu(I)-Catalyzed Click Reactions for Self-Healing Polymers

Systematic investigations on the Cu(I)-catalyzed click reaction between a three-arm star polymer and low-molecular-weight alkynes are described. Liquid trivalent alkynes (27) are reacted either with monovalent azidotelechelic polyisobutylene 1b ($ \overline M_{\rm n} $ = 1900 g mol-1, PDI = 1.3) in solution, or with the trivalent azidotelechelic polyisobutylene 1a ($ \overline M_{\rm n} $ = 4000 g mol-1, PDI = 1.3). A significant autoacceleration is observed leading to increased reaction rates of the mono-, di-, and trisubstituted alkynes. Reaction in the solvent-free state proved to be significantly faster than reaction in solution. Upon testing various Cu(I) catalysts, CuBr(PPh3)3, tripropargylamine 2 emerges as the ideal component for a room-temperature click reaction with the three-arm star polyisobutylene 1a.