### 脯氨酸聚酯的单链力学性质

1. a西南交通大学 生命科学与工程学院 成都 610031
b北京大学 化学与分子工程学院 北京 100871
• 投稿日期:2021-11-14 发布日期:2021-12-21
• 通讯作者: 吕华, 崔树勋
• 基金资助:
项目受国家自然科学基金(21774102)

### Single-chain Mechanics of Proline-based Polyesters

Zheng Gonga, Yi Zhangb, Hua Lub(), Shuxun Cuia()

1. aSchool of Life Science and Engineering, Southwest Jiaotong Universitiy, Chengdu 610031, China
bCollege of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
• Received:2021-11-14 Published:2021-12-21
• Contact: Hua Lu, Shuxun Cui
• Supported by:
National Natural Science Foundation of China(21774102)

Proline-based polyesters (PPEs) are novel degradable aliphatic polyesters with high molecular weight and complete recyclability under mild and economic conditions. Because of that, PPEs can be used as a candidate to solve the environmental problems caused by the petroleum-based synthetic polymers. However, the study of the mechanical property of PPEs, which is important for the applications, has not been reported yet. Herein, we utilized atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) and quantum mechanics (QM) calculations to study the mechanical property of PNC12PE (a kind of PPEs) in polar organic solvent at the single-molecule level. PNC12PE was dissolved in methyl isobutyl ketone (MIBK) to a concentration of 10 μg/mL. To prepare the sample for single-molecule AFM, a few drops of the PNC12PE solution were deposited onto the clean glass substrate for 15 min. Then, the sample was rinsed with abundant ethanol to remove the loosely adsorbed polymer. After being dried by air flow, the sample was immediately used in the experiments. The spring constant of each AFM cantilever, which was around 45 pN/nm, was obtained by the thermo- excitation method. No remarkable differences can be found between different force-extension (F-E) curves with various stretching velocities, suggesting that the single-molecule experiments were carried out under quasi-thermodynamic equilibrium conditions. It is found that the experimental single-chain elasticity of PNC12PE consists with the result of the QM calculations and the Kuhn length is structural relevant, indicating that the inherent elasticity of PNC12PE is obtained. The normalized F-E curves of PNC12PE and the QM-freely rotating chain (FRC) model fitting curve of C—C backbone (polyethylene) have little difference, meaning that the main chain of PNC12PE is as soft as the common polymers with C—C backbone. In addition, the pyrrolidine rings in the main chain of PNC12PE are mechanically stable (F<2200 pN) during SMFS experiment, indicating that PNC12PE is suitable for the applications requiring high mechanical stability.