Modulating Catalytic Activity of Polymer-Based CuAAC "click" Reactions

The copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction is used to synthesize complex polymer architectures. In this work, we demonstrate the control of this reaction at 25 degrees C between polystyrene (PSTY) chains through modulating the catalytic activity by varying the combinations of copper source (i.e., Cu(I)Br or copper wire), ligand (PMDETA and/or triazole ligand), and solvent (toluene or DMF). The fastest rate of CuAAC was found using Cu(I) Br/PMDETA ligand in toluene, reaching near full conversion after 15 min at 25 degrees C. For the same catalysts system, DMF also gave fast rates of "click" (95% conversion in 25 min). Cu(0) wire in toluene gave a conversion of 98% after 600 min, a much higher rate than that observed for the same catalyst system used in DMF. When the PSTY had a chemically bound triazole ring close to the site of reaction, the rate of CuAAC in toluene increased significantly, 97% in 180 min at 25 degrees C, in agreement with our previously published results. This suggests that rapid rates can be obtained using copper wire and will have direct applications to the synthesis of compound where air, removal of copper, and reuse of the copper catalyst are required. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4539-4548, 2011