Acta Chimica Sinica ›› 2020, Vol. 78 ›› Issue (11): 1235-1239.DOI: 10.6023/A20080339 Previous Articles     Next Articles



李荣烨, Khiman Mehul, 盛力, 孙静   

  1. 青岛科技大学高分子科学与工程学院 青岛 266042
  • 投稿日期:2020-08-01 发布日期:2020-09-04
  • 通讯作者: 孙静
  • 基金资助:
    项目受国家自然科学基金(Nos.51722302 and 21674054)和山东省自然科学基金(No.ZR2019JQ17)资助.

pH/Solvent Tunable Hierarchical Nanostructures Assembled from an Amphiphilic Polypeptide-containing Triblock Copolymer

Li Rongye, Khiman Mehul, Sheng Li, Sun Jing   

  1. College of Polymer Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, China
  • Received:2020-08-01 Published:2020-09-04
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Nos. 51722302 and 21674054) and the Natural Science Foundation of Shandong Province (No. ZR2019JQ17).

Similar to natural proteins, polypeptides can form secondary structures depending on their physical properties. Many efforts have been made towards the self-assembly of triblock copolymer containing polypeptide as an important component to construct hierarchical structures by utilizing the pH-responsive conformation transformation. In this work, a pH-responsive poly(ethylene glycol)-b-poly(L-lysine)-b-poly(styrene) (PEG-b-PLL-b-PS) triblock copolymer was prepared via a combination of controlled ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP). In the triblock copolymer, PLL is water-soluble in acidic solution with random coil conformation, but becomes insoluble helix in alkaline solution. PEG has excellent water solubility that can exhibit protein-resistant property. PS serves as hydrophobic part. Self-assembly of the polymer was examined by transmission electron microscopy (TEM), atomic force microscopy (AFM) and attenuated total reflection-infrared spectrometer (ATR-IR). The triblock copolymer forms spherical micelles in 1:1 volume ratio of tetrahydrofuran-water mixed solvent, in which the hydrophobic PS segment forms a core and the two hydrophilic segments PLL and PEG serve as shell and corona, respectively. The spheres as the subunits further transform into hierarchical 1D fiber-like structure in the presence of THF after 7 d of aging, confirmed by both TEM and AFM techniques. Upon removing THF, the spherical shape was re-obtained with slightly smaller diameter, so called “frozen micelles”. Further, the diameter of the spheres increases with pH increasing. A sphere-to-vesicle transition was observed at pH 13 as the secondary conformation of PLL transforms from coil to α-helix. The dialysis of these solutions can convert the vesicles back into spherical morphology with slightly smaller diameter.

Key words: triblock copolymer, ring-opening polymerization, atom transfer radical polymerization, self-assembly, pH responsive, nanostructure