Synthesis of Photoisomerizable Block Copolymers by Atom Transfer Radical Polymerization

✍ Scribed by Chih-Feng Huang; Wei Chen; Thomas P. Russell; Anna C. Balazs; Feng-Chih Chang; Krzysztof Matyjaszewski

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 464 KB
• Volume: 210
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200900195

✦ Synopsis

Abstract

A series of polystyrene‐block‐poly(n‐butyl methacrylate) (PS‐b‐P__n__BMA) diblock copolymers (di‐BCPs) with an azobenzene moiety [trans‐4‐methacryloyloxyazobenzene (MOAB)] in the P__n__BMA segment was prepared by atom transfer radical polymerization (ATRP). P(__n__BMA‐co‐MOAB) macroinitiators were prepared by activators regenerated by electron transfer (ARGET) ATRP. The MOAB was slightly more reactive than __n__BMA, resulting in a weak gradient fashion of copolymer. The macroinitiators were subsequently chain‐extended with styrene. Acceleration of the ATRP rate was observed in the presence of a reducing agent. P(__n__BMA‐co‐MOAB)‐b‐PS di‐BCPs were obtained with relatively narrow molecular weight distributions ($\overline M _{\rm w}$/$\overline M _{\rm n}$ = 1.16–1.49) and the molecular weights were in good agreement with the theoretical values. The efficiency of photoisomerization of the MOAB units was above 80%. DSC traces showed a single T~g~ suggesting the block copolymers were miscible before UV irradiation. After UV irradiation, the X‐ray reflectivity measurements showed the beating of two frequencies, indicating the formation of island‐hole structure.

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