Precise Synthesis of ABCDE Star Quintopolymers by Combination of Controlled Polymerization and Azide-Alkyne Cycloaddition Reaction

A facile approach based on integrated utilization of ring-opening polymerization (ROP), reversible addition-fragmentation chain transfer (RAFT) process, and azide-alkyne cycloaddition reaction was efficiently used to construct amphiphilic 5-arm ABCDE star quintopolyrners. The miktoarm stars are composed of poly(ethylene glycol) (A), poly(epsilon-caprolactone) (B), polystyrene (C), poly(L-lactide) (D), poly(N,N-dimethylaminoethyl methacrylate) (E-1), poly(methyl methacrylate) (E-2), and poly(methyl acrylate) (E-3). Alkyne-in-chain-functionalized BC and DE diblock copolymers were synthesized by successive ROP and RAFT process. Selective [3 + 2] click reaction between two-azide-end-functionalized PEG and BC copolymer gave azide-core-functionalized ABC star terpolymer, and a subsequent click reaction with DE copolymer afforded well-defined ABCDE stars with well-controlled molecular weight, low polydispersity, and precise composition, as evidenced from H-1 NMR, GPC, and GPC-MALLS analyses. DSC analyses revealed part of polymer segments in ABCDE stars were compatible. This general methodology has some advantages such as straightforward synthesis, mild reaction conditions, versatile polymerizable monomers, and high yields, which is promising for the construction of numerous functional star copolymers with multiple compositions and precise microstructures.