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

• Azobenzene-containing polyethersulfone with various spacer lengths was synthesized.
• All polymers show good thermal stability.
• The influence of spacer length on photoresponsive behavior was investigated.
• The photoisomerization was more difficult to be induced for azobenzene-containing poly (ether sulfone)s with shorter spacers.
• All polymers possessed remnant values of birefringence larger than 84% of the saturation values of birefringence.

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.