Synthesis of well-defined polystyrene-b-aromatic polyether using an orthogonal initiator for atom transfer radical polymerization and chain-growth condensation polymerization

Well-defined diblock copolymers of polystyrene and aromatic polyether were synthesized by the combination of atom transfer radical polymerization (ATRP) and chain-growth condensation polymerization (CGCP) from an orthogonal initiator. A polystyrene macroinitiator was first synthesized by the ATRP of styrene in the presence of 4-fluorobenzenesulfonyl chloride (FBS-Cl) as an orthogonal initiator, then the terminal chlorine of the polystyrene was dehalogenated with Et3SiH/Pd(OAc)(2). The CGCP of potassium 5-cyano-4-fluoro-2-propylphenolate (1) was then carried out with the polystyrene macroinitiator in sulfolane at 150 degrees C. However, not only polystyrene-b-aromatic polyether but also macrocycles of 1 were obtained, due to transetherification of the p-sulfonylphenyl ether linkage of the macroinitiator with 1. In contrast, the CGCP of 1 from another polystyrene macroinitiator bearing a keto group, which was prepared similarly by the ATRP of styrene with 4-(1-bromoethyl)-4'-fluorobenzophenone (FBP-Br) as an orthogonal initiator, followed by reduction of the terminal C-Br bond with Bu3SnH, afforded only well-defined polystyrene-b-aromatic polyether. This diblock copolymer self-assembled in THF to form spherical aggregates.