RAFT Polymerization of "Splitters" and "Cryptos" Exploiting Azole N carboxamides As Blocked Isocyanates for Ambient Temperature Postpolymerization Modification
A postpolymerization modification strategy based on ambient temperature nucleophilic chemical deblocking of polymer scaffolds bearing N heterocycle blocked isocyanate moieties is reported. Room temperature RAFT polymerization of three azole N carboxamide methacrylates, including 3,5 dimethylpyrazole, imidazole, and 1,2,4 triazole derivatives, afforded reactive polymer scaffolds with well defined molecular weights and narrow dispersities (D 1.2) Model analogues possessing the same N heterocycle blocking agents with varied leaving group abilities were synthesized to determine optimal deblocking conditions. The reactivity of the azole N carboxamide moieties toward nucleophiles can be tuned simply by varying the structure of the azole blocking agents (reactivity order: pyrazole imidazole triazole) DBU catalyzed reactions of thiols with imidazole and 1,2,4 triazole blocked isocyanate scaffolds were shown to occur rapidly and quantitatively under ambient conditions. Differences in reactivity of 1,2,4 t.