文献类型：期刊文献

英文题名：Synthesis and Self-assembly of Amphiphilic Alternating Azopolymers

作者：Jin, Sheng[1];Lu, Yun-kai[1];Tao, Xin-feng[1];Lin, Shao-liang[1]

机构：[1]East China Univ Sci & Technol, Sch Mat Sci & Engn, Shanghai Key Lab Adv Polymer Mat, Shanghai 200237, Peoples R China

年份：2026

卷号：57

期号：8

起止页码：1740

外文期刊名：ACTA POLYMERICA SINICA

收录：;WOS:【SCI-EXPANDED(收录号:WOS:001840813500010)】；

语种：英文

外文关键词：Azobenzene; Ugi reaction; Alternating copolymer; Self-assembly; Photo-responsiveness

摘要：Alternating azopolymers are prominent in the field of smart material design due to their distinctive self-assembly behavior, which originates from the precisely regulated solvophilic/solvophobic balance and their responsiveness to stimuli. However, the azobenzene-functionalized alternating copolymers reported thus far are predominantly synthesized through complex and time-consuming methods. In this work, novel amphiphilic alternating azopolymers, P(Azo-alt-EG(m)) (m=2, 3, 4, and 5), were prepared via Ugi multicomponent polymerization using commercially available monomers, including azobenzene-4,4'-dicarboxylic acid (Azo), oligo(ethylene glycol) diamines (EG(m)), benzaldehyde, and tert-butyl isocyanide. The polymerizations proceeded successfully, affording relatively high yields (>74%). The chemical structures, molecular weights (MWs) and MW distributions were verified through & sup1;H-NMR and SEC analyses. The resulting copolymers exhibited a comparable MW range, spanning from 11.9 kg/mol to 13.3 kg/mol. UV-Vis spectroscopy demonstrated that P(Azo-alt-EG(m)) possessed excellent photo-isomerization properties. As the value of m increased from 2 to 5, the rates of photo-induced trans-to-cis isomerization of P(Azo-alt-EG(m)) were (0.418 +/- 0.023), (0.461 +/- 0.011), (0.528 +/- 0.043), and (0.660 +/- 0.013) s(-1,) respectively. This trend was attributed to the longer EG chains providing more free space for the azobenzene groups to move. The thermal annealing-induced self-assembly behaviors of P(Azo-alt-EG(m)) in alcoholic solvents were systematically investigated. Firstly, P(Azo-alt-EG(m)) was dissolved in ethanol at 70 degrees C and maintained for 4 h, followed by incubating at 25 degrees C for 24 h. This process led to the formation of uniform polymersomes with hydrodynamic radius (R-h) ranging from 95.4 nm to 148.0 nm, depending on the increasing length of EG chains. Meanwhile, when annealed from 90 degrees C in n-propanol, P(Azo-alt-EG(m)) formed fusiform nanosheets, with sizes tunable according to the length of the EG chains. In both polymersomes and nanosheets, P(Azo-alt-EG(m)) chains are orderly arranged following a folded chain model, adopting a monolayer core-shell structure. UV-Vis spectroscopy revealed that the azobenzene groups within the assemblies had a H-aggregation. These assemblies exhibited remarkable photo-responsiveness, undergoing morphological transitions under ultraviolet/visible light irradiation. Specifically, polymersomes disintegrated into irregular aggregates under 365 nm UV light irradiation and reformed into larger polymersomes under 450 nm visible light irradiation, while fusiform nanosheets transformed into spherical micelles and subsequently into elongated "bamboo leaf" -like nanosheets. These findings indicate promising applications for P(Azo-alt-EG(m)) assemblies in the fields of smart materials and biomedicine.