间规聚丙烯单晶纳米力学性质的单分子力谱研究

发布时间：2018-06-25 02:10

本文选题：原子力显微镜 + 单分子力谱　；参考：《吉林大学》2017年硕士论文

【摘要】：半结晶性高分子材料因其优良的性能和使用价值而被广泛应用到人类生活中的多个领域。结晶相结构对高分子材料许多方面力学性质起决定作用。随着人们对材料应用性能要求的进一步提高,揭示并调控材料晶体结构-性能的关系,尤其是单分子水平结构与材料宏观性能关系的探索,变得非常重要。相关研究有助于更好地理解材料性能变化的微观机理,从而指导高性能高聚物晶体材料的性能调控及设计与制备。传统的实验方法难以给出分子水平的力学性质信息,基于原子力显微镜(AFM)的单分子力谱技术(SMFS)的出现使相关研究成为可能。在本论文第一章中,系统地介绍了高分子结晶态及AFM成像的工作模式及其应用,并对基于AFM的单分子力谱技术做了详细的描述,包括其工作原理、单分子力-拉伸曲线的获取、判定与分析及其在材料科学领域的重要应用。本论文的研究思路主要是借助于AFM的单分子力谱技术,探究间规聚丙烯(s PP)晶体材料不同微观结构的力学性能。本论文第二章的工作主要集中在具有不同晶型结构的间规聚丙烯单晶的制备与表征。通过结晶条件筛选,分别制备出不同晶型结构的间规聚丙烯溶液相单晶和熔融相单晶,并利用AFM、透射电子显微镜(TEM)、X-射线粉末衍射仪(XRD)、电子衍射(ED)等测试手段对间规聚丙烯单晶的形貌和晶体结构进行表征,结果表明成功制备了不同结构的间规聚丙烯单晶,为其微观尺度力学性质研究奠定了基础。第三章中主要是间规聚丙烯晶体单分子力谱实验的设计、实施与数据分析。经过多次实验条件的摸索,建立了聚丙烯分子与AFM针尖的有效偶联方法。通过分别对AFM探针针尖和间规聚丙烯单晶表面修饰氨基和羟基(磺酸基),增强针尖与聚丙烯的结合强度,使两者之间可以形成桥联结构;随后分别对具有不同晶型结构的间规聚丙烯单晶进行表面随机拉伸,得到单分子链力-拉伸曲线,从单分子水平上探究将单个聚丙烯链从晶体中解折叠的力学性能,同时对间规聚丙烯其他聚集态结构(球晶结构、介晶相结构)也进行了探究。结果表明,不同晶型结构的间规聚丙烯具有不同的力学稳定性,I型单晶单分子力学稳定性最强;间规聚丙烯单晶力学性能具有晶体厚度依赖性;位于晶体不同晶面中的s PP分子体现出相近的纳米力学性质。上述实验结果从分子水平上加深了我们对间规聚丙烯结构与力学性质关系的认识,为间规聚丙烯材料的性能优化与调控提供了重要依据。
[Abstract]:Semi-crystalline polymer materials are widely used in many fields of human life because of their excellent properties and use value. Crystalline phase structure plays a decisive role in many aspects of mechanical properties of polymer materials. With the further improvement of material application performance, it is very important to reveal and regulate the relationship between crystal structure and properties, especially the relationship between the horizontal structure of single molecule and the macroscopic properties of materials. The related studies are helpful to better understand the microscopic mechanism of the change of material properties, and thus guide the performance control, design and preparation of high performance polymer crystal materials. The traditional experimental methods are difficult to give the information of the mechanical properties at the molecular level. The appearance of single molecular force spectroscopy (SMFS) based on atomic force microscope (AFM) makes the related research possible. In the first chapter of this thesis, the working mode and application of polymer crystalline state and AFM imaging are systematically introduced, and the single molecular force spectrum technology based on AFM is described in detail, including its working principle, the acquisition of single molecular force-tensile curve. Judgment and Analysis and its important Application in the Field of Materials Science. The main idea of this thesis is to explore the mechanical properties of syndiotactic polypropylene (SPP) crystal materials with the help of AFM single molecule force spectroscopy. The second chapter focuses on the preparation and characterization of syndiotactic polypropylene single crystals with different crystal structure. Through the screening of crystallization conditions, the syndiotactic polypropylene solution phase single crystals and the melt phase single crystals with different crystal structure were prepared, respectively. The morphologies and crystal structures of syndiotactic polypropylene single crystals were characterized by AFM, transmission electron microscopy (TEM) X-ray powder diffraction (XRD) and electron diffraction (Ed). The results showed that syndiotactic polypropylene single crystals with different structures were successfully prepared. It lays a foundation for the study of micro-scale mechanical properties. The third chapter is mainly about the design, implementation and data analysis of single molecule force spectrum experiment of syndiotactic polypropylene crystal. An effective coupling method between polypropylene molecule and AFM tip was established after many experiments. The surface modification of amino group and hydroxyl group (sulfonic group) on the tip of AFM probe and syndiotactic polypropylene single crystal were carried out to enhance the bonding strength between the tip and polypropylene, so that the bridging structure could be formed between them. Then the surface of syndiotactic polypropylene single crystal with different crystal structure was drawn randomly, and the single molecular chain force tensile curve was obtained. The mechanical properties of unfolding single polypropylene chain from crystal were explored from the single molecule level. At the same time, the other aggregation structure (spherulite structure, mesomorphic phase structure) of syndiotactic polypropylene was also studied. The results show that the syndiotactic polypropylene with different crystal structure has different mechanical stability and the mechanical properties of syndiotactic polypropylene single crystal are dependent on crystal thickness. The SPP molecules located in different crystal planes exhibit similar nanomechanical properties. The above experimental results deepen our understanding of the relationship between the structure and mechanical properties of syndiotactic polypropylene at the molecular level and provide an important basis for the performance optimization and control of syndiotactic polypropylene materials.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O632.12

【相似文献】