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The research on multi‐responsive azobenzene block copolymer and its self‐assembly behavior
Author(s) -
Cao Ying,
Cao Jie,
Zhang Jiatian,
Zhang Dandan,
Li Meng,
Xu Yiting,
He Kaibin,
Chen Guorong,
Yuan Conghui,
Dai Lizong
Publication year - 2020
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.4812
Subject(s) - azobenzene , copolymer , micelle , nile red , amphiphile , chain transfer , materials science , polymer chemistry , raft , ethylene glycol , acrylic acid , polymerization , molecule , photochemistry , chemistry , radical polymerization , organic chemistry , polymer , aqueous solution , fluorescence , physics , quantum mechanics , composite material
The azobenzene‐based amphiphilic copolymers have drawn significant attention as a kind of multi‐responsive smart materials. The demand on deeper investigation of how the azobenzene group influences the micelles formation and light‐responsive behavior on molecular level is very urgent. In this article, multi‐responsive block copolymers, poly (acrylic acid)‐block‐poly[4'‐[[(2‐Methacryloyloxy)ethyl]ethylainino]azobenzene‐co‐poly (ethylene glycol) methyl ether methacrylate] (PAA‐b‐P (AzoMA‐co‐PEGMA)), with pH‐, light‐ and reduction‐responsiveness were synthesized by the monomers of AzoMA, PEGMA and acrylic acid via reversible addition‐fragmentation chain transfer polymerization (RAFT). The amphiphilic block copolymer presented aggregation‐induced emission effect, and it was pH, light, and reduction responsive. The results showed that the micelle size decreased with the decreasing of pH within a certain range. However, the particle size of micelles increased significantly when the pH was 4. Once adding reduction agent, the micelles were disassembly. Fluorescent molecule of Nile red was selected as a hydrophobic guest molecule to study the properties of encapsulating and releasing abilities of block copolymer micelles for guest molecules. The results showed that the loading capacity of three kinds of copolymer micelles was closely related to the aggregates formed by the hydrophobic block, mainly azobenzene block. Besides, the block copolymer micelles could release a certain amount of Nile red under the irradiation of UV light, the reduction with Na 2 S 2 O 4 as reductant, and the exposure to alkaline environment. The mechanism of how the different status of azobenzene group influenced the self‐assembly and multi‐responsive behavior was explored on molecular level.