### 两亲性聚氨基酸三嵌段共聚物构筑pH/溶剂可控多级纳米结构

1. 青岛科技大学高分子学院 青岛 266042
• 发布日期:2020-09-04
• 通讯作者: 孙静 E-mail:jingsun@qust.edu.cn
• 基金资助:
本项目感谢国家自然科学基金（Nos 51722302 and 21674054），山东省杰青基金项目（No.ZR2019JQ17）资助.

### pH/solvent tunable hierarchical nanostructures assembled from an amphiphilic polypeptide-containing triblock copolymer

Li Rongye, Mehul Khiman, Sheng Li, Sun Jing

1. College of Polymer Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042
• Published:2020-09-04
• Supported by:
Project supported by the National Natural Science Foundation of China (Nos 51722302 and 21674054), 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. Note that PS is a glassy polymer at room temperature. Thus, the addition of THF that can dissolve PS is desired to reach an equilibrium in aqueous solution. We demonstrated that the nanostructured self-assemblies can be used as the subunits to construct 1D fiber-like supramolecular structure in water-THF mixed solvent.Self-assembly of the polymer was examined in aqua-organic mixed solution 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 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 days 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.