Investigating polymer crystallization at the nanoscale using AFM-IR

控制聚合物和复合材料的形态和结晶至关重要，因为它直接关系到材料的最终性能。半结晶聚合物是商业聚合物的重要部分。众所周知，可混溶的聚合物共混物可以具有多种形态和结晶机制，这取决于每种组分的熔融温度、共混物组成和结晶条件的差异。这些现象在可混溶和可结晶聚合物的二元共混物中变得更加复杂，其中两种组分竞争以达到最终结构（例如形状、取向、形态、形貌、纹理和密度）。然而，尽管物理化学表征方法取得了进展，但在可结晶聚合物共混物中聚合物分布的检查，特别是在亚微米级，在技术上是困难的。最近，我们已经能够使用一种先进的设备，即原子力显微镜-红外光谱（AFM-IR），以研究聚合物的结晶和纳米扩散在互溶和不互溶的共混物，同时记录其高分辨率的形貌图像在纳米尺度上。通过AFM-IR定性鉴定化合物的化学组成的能力使这一进步成为可能。初步结果导致了几个出版物和奖项。在这项研究计划中，我们将开发新的方法来更好地了解可生物降解聚合物的可降解性，结晶和分布，特别是在纳米级的二元聚合物共混物，主要使用原子力显微镜结合红外光谱（AFM-IR）或热电偶（Nano-TA）。将进行聚合物共混物的动力学模拟，以了解结晶过程中的分子结构，主要使用专用于聚合物和生物分子的大规模原子/分子大规模并行模拟器（LAMMPS）分子动力学模拟器软件。纳米尺度表征方法有助于更好地回答文献中的开放问题，特别是分子排列，片层发展机制，球形结构中的形态和相变，这些都是检测生物聚合物材料最终行为的更重要特征。了解聚合物共混物中聚合物扩散与球晶结构和操作条件的关系将提供重要的科学贡献，并为三元和四元共混物等复杂体系的结晶研究开辟新途径。改善聚合物共混物的性能将扩大这些生物聚合物在各种应用中的应用领域，如生物医学材料和生物组织（2019年全球市场为254亿美元）。

Controlling the morphology and crystallization of polymers and composites is crucial because it is directly related to the final properties of the material. Semi-crystalline polymers are an important fraction of commercial polymers. It is well known that miscible polymeric blends can have a variety of morphologies and crystallization mechanisms that depend on the difference in the melting temperature of each component, the blend composition and the crystallization conditions. These phenomena become more complex in the binary blends of miscible and crystallizable polymers where the two components are in competition to reach the final structure (e.g. shape, orientation, morphology, topography, texture and density). However, the examination of the distribution of polymers in crystallizable polymer blends, especially at the submicron scale, is technically difficult despite the progress of the physicochemical characterization methods. Recently, we have been able to use an advanced equipment, i.e. atomic force microscopy-infrared spectroscopy (AFM-IR), to study the crystallization and nano-diffusion of polymers in miscible and immiscible blends, while recording their high-resolution topographic images at the nanoscale level. This advancement was made possible through the ability to qualitatively identify the chemical composition of the compound through AFM-IR. The preliminary results have led to several publications and awards. In this research program, we will develop new approaches to better understand the miscibility, crystallization and distribution of biodegradable polymers, particularly the binary polymeric blends at the nanoscale level using mainly atomic force microscopy coupled with an infrared spectroscopy (AFM-IR) or a thermocouple (Nano-TA). The simulation of the dynamics of the polymer blends will be carried out in order to understand the molecular structure during the crystallization using mainly the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) Molecular Dynamics Simulator software dedicated to polymers and biomolecules. Nanoscale characterization methods help to better answer the open questions in the literature, particularly the molecular arrangements, lamella development mechanisms, morphology and phase transition in a spherical structure that are more important features to detect the final behavior of biopolymer materials. Understanding the diffusion of polymers in relation to the structure of spherulites and the operating conditions in polymer blends will provide an important scientific contribution and open a new pathway for crystallization studies in complex systems, such as ternary and quaternary blends. Improving the properties of the polymer blends will extend the field of use of these biopolymers in various applications such as in biomedical materials and biological tissues (globally, market of US$25.4 billion for 2019).