Wang Jiadong, Wang Min, Zhang Xi, Han Yang, Wu Yingxue, Wang Dong, Qin Xuan, Lu Yonglai, Zhang Liqun
State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China.
Engineering Research Center of Elastomer Materials Energy Conservation and Resources, Ministry of Education, Beijing 100029, China.
ACS Appl Mater Interfaces. 2023 Sep 27;15(38):45388-45398. doi: 10.1021/acsami.3c07860. Epub 2023 Sep 13.
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 into its hierarchical structure and establishes a quantitative framework to explore the intricate relationship between the structure and properties.
具有微相分离结构的聚氨酯（PU）因其高度可设计的分子结构和广泛可调的性能而备受关注。然而，目前缺乏用于量化PU微相分离的系统方法。为了填补这一研究空白，我们利用原子力显微镜（AFM）纳米力学映射技术结合高斯拟合对PU微相分离的演变进行重新着色和定量分析。通过改变扩链剂与交联剂的比例，我们观察到软硬段之间氢键的变化。随着扩链剂与交联剂比例的降低，氢键强度减弱，导致硬段（HS）域的数量和相百分比减少。因此，软硬段之间的微相分离程度降低，导致材料的力学性能和动态粘弹性发生特定变化。为了进一步研究PU的层级结构，我们采用了各种技术，如X射线分析、透射电子显微镜（TEM）和基于AFM的红外光谱（AFM-IR）。我们的研究结果揭示了HS域内由片晶组成的球晶图案，交联密度从中心到外围逐渐增加。总体而言，我们对PU的全面表征为其层级结构提供了有价值的见解，并建立了一个定量框架来探索结构与性能之间的复杂关系。
