Quantification Characterization of Hierarchical Structure of Polyurethane by Advanced AFM and X-ray Techniques

作者：Jiadong Wang, Min Wang, Xi Zhang, Yang Han, Yingxue Wu, Dong Wang, Xuan Qin, Yonglai Lu, Liqun Zhang · 发表于：ACS Applied Materials & Interfaces · 年份：2023 · DOI：10.1021/acsami.3c07860 · 被引用次数：59 · 研究领域：Force Microscopy Techniques and Applications、Polymer composites and self-healing、Polymer crystallization and properties

Polyurethane (PU) with microphase separation has garnered significant attention due to its highly designable molecular structure and a wide range of adjustable properties. However, there is currently a lack of systematic approaches for quantifying PU's microphase separation. To address this research gap, we utilized an atomic force microscopy (AFM) nanomechanical mapping technique along with Gaussian fitting to recolor and quantitatively analyze the evolution of PU's microphase separation. By varying the ratios of the chain extender to cross-linking agent, we observed the changes in the hydrogen bonding between the soft and hard segments. As the ratio of the chain extender to cross-linking agent decreases, the strength of the hydrogen bonding weakens, resulting in a reduction in the quantity and phase percentage of hard segment (HS) domains. Consequently, the degree of microphase separation between the soft and hard segments decreases, leading to specific alterations in the material's mechanical properties and dynamic viscoelasticity. To further investigate the hierarchical structure of PU, we employed various techniques, such as X-ray analysis, transmission electron microscopy (TEM), and AFM-based infrared spectroscopy (AFM-IR). Our findings reveal a spherulite pattern composed of lamellae within the HS domains, with the cross-linking density gradually increasing from the center to the periphery. Overall, our comprehensive characterization of PU provides valuable insights in...