Li Jie, Wang Meng-Wie, Liu Ye, Ren Wei-Min, Lu Xiao-Bing
State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China.
Angew Chem Int Ed Engl. 2021 Aug 9;60(33):17898-17903. doi: 10.1002/anie.202104750. Epub 2021 Jul 12.
We report the synthesis of isotactic azobenzene-based polyesters (azopolyesters) with main-chain chirality via highly enantioselective resolution copolymerization of racemic azobenzene-containing epoxides with cyclic anhydrides. All polyesters with trans-azobenzene moieties were found to be semicrystalline materials with melting temperatures of 153-231 °C, while the corresponding isotactic cis-azopolyesters were amorphous. The azobenzene groups in the copolymers exhibited reversible trans-to-cis and cis-to-trans photoisomerization upon irradiation with light. This demonstrates that the crystallinity of isotactic azopolyesters can be manipulated via photoinduced reversible isomerization. In addition, mixing isotactic trans-polyesters with different enantiomeric configurations in a 1:1 mass ratio afforded crystalline stereocomplexes for which the crystalline behavior differed significantly from those of the component enantiomer. Also, photoinduced reversible transitions between semicrystalline and amorphous states were observed in various stereocomplexes of isotactic trans-azopolyesters, similar to the isotactic azopolyesters themselves.
我们报道了通过外消旋含偶氮苯环氧化物与环状酸酐的高度对映选择性拆分共聚反应，合成具有主链手性的全同立构偶氮苯基聚酯（偶氮聚酯）。发现所有含有反式偶氮苯基团的聚酯都是半结晶材料，熔点为153 - 231 °C，而相应的全同立构顺式偶氮聚酯是无定形的。共聚物中的偶氮苯基团在光照下表现出可逆的反式到顺式和顺式到反式光异构化。这表明全同立构偶氮聚酯的结晶度可以通过光诱导可逆异构化来控制。此外，将不同对映体构型的全同立构反式聚酯按1:1质量比混合，得到了结晶立体复合物，其结晶行为与组分对映体的结晶行为有显著差异。同样，在全同立构反式偶氮聚酯的各种立体复合物中观察到了半结晶态和无定形态之间的光诱导可逆转变，这与全同立构偶氮聚酯本身类似。
