Synthesis, characterization, and photoresponsive behavior of a series of azobenzene-containing side-chain poly(ether sulfone)s with various lengths of flexible spacers

摘要

A series of azobenzene-containing side-chain poly(ether sulfone)s (azo-PES) with various spacer lengths (2, 6 or 12 methylene units) were successfully synthesized via a nucleophilic substitution grafting reaction between poly(ether sulfone)s with hydroxylphenyl side groups and azobenzene monomers. Their chemical structures and properties were characterized by means of IR, UV-vis and ~1H NMR. These azo-polymers show good thermal stability with glass transition temperatures and 5% weight-loss temperatures above 119 °C and 347 °C, respectively. The results of photoisomerization experiments indicated that azo-PES polymer with longer spacers correspond to higher photoisomerization rates. Upon irradiation with a 532 nm neodymium doped yttrium aluminum garnet (Nd:YAG) laser beam, they presented remnant values of birefringence larger than 82% of the saturation value of birefringence, indicating the good stability of the photoinduced orientation. No fatigue phenomena have been observed after several cycles of inscription-erasure-inscription sequences.