A TEMPO-mediated “living” free-radical approach to ABA triblock dendritic linear hybrid copolymers

✍ Scribed by Todd Emrick; Wayne Hayes; Jean M. J. Fréchet

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 175 KB
• Volume: 37
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19991015)37:20<3748::aid-pola2>3.0.co;2-h

✦ Synopsis

Dumbbell-shaped ABA triblock copolymers composed of benzyl ether dendrons and polystyrene as the A and B blocks, respectively, were prepared using 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) -mediated "living" free-radical polymerization. A new bis-dendritic unimolecular initiator, compound 3, was employed to study the efficiency of ABA triblock formation under standard TEMPO-mediated polymerization conditions. By this design, the central B block of the ABA triblock copolymer was grown into the bis-dendritic unimolecular initiator. The ABA triblock copolymer products were separated from their by-products, AB diblock copolymers, by column chromatography on silica gel. The isolated copolymers were characterized using gel permeation chromatography and proton nuclear magnetic resonance spectroscopy as complimentary techniques. That the dendritic-linear AB diblock copolymer was obtained in a mixture with ABA triblock material indicates that TEMPO-terminated dendron counter-radical 5 is an imperfect mediator of this free-radical polymerization.