AFM单分子力谱研究孤立聚合物分子玻璃化转变动力学

理解孤立聚合物分子玻璃化转变动力学，探索其偏离本体的物理本质，对于精准调控纳米受限条件下聚合物玻璃化转变和分子运动、设计与开发相关材料具有重要的意义。然而，传统表征技术的空间分辨率制约了受限聚合物链动力学的直接测量，尤其是界面对动力学的影响至今仍未被定量表征。.本项目将设计单分子信号易指认、不受探针界面影响的嵌段聚合物体系，利用单晶和LB膜调控链末端活性基团密度、束缚其迁移，实现探针顶端的单分子高效偶联，建立高效空气相单分子力谱技术；发展用于研究孤立聚合物分子玻璃化转变动力学的实验方法和基于单晶模型体系的复杂数据解析方法。利用新建立的技术与方法定量界面作用、链组成、分子量和构象复杂度对玻璃化转变动力学的影响；并关联不同环境（溶剂、空气、薄膜及结晶-无定形网络）中分子间相互作用及链段动力学性质；结合粘弹性测量和调幅-调频AFM等技术，探索不同尺度（链段和分子尺度）的玻璃化转变动力学性质。

Understanding the glass transition kinetics of isolated polymer molecules and exploring the physical nature of their departure from the bulk are of great significance for accurately controlling the glass transition and molecular motion of polymers that are subject to confinement and/or finite size effects, designing and developing the related materials. However, the spatial resolution of traditional characterization techniques limit the direct measurement of the dynamics of confined polymer chains, especially the effect of interface on the dynamics has not been quantitatively characterized..In this project, we will design a block polymer system which can easily identify the single molecule signal and is not affected by the probe interface. To couple the single molecule at the top of the AFM tip, we use single crystal and LB film to regulate the density of the active groups at the end of the chain and restrain their migration. By this way, we establish the high-efficiency air-phase single molecule force spectroscopy. We also develop the experimental methods for studying the glass transition kinetics of isolated polymer molecules and use the single crystal as a model system to analyse the complex data. Then, we use the newly established techniques and methods to quantify the effects of interfacial interaction, chain composition, molecular weight and conformational complexity on glass transition kinetics; correlate the intermolecular interactions and segment dynamics in different environments (solvent, air, film and crystalline amorphous network). The viscoelasticity measurement and AM-FM AFM techniques were combined to explore the kinetic properties of glass transition at the different scales.