Synthesis, Structure, Properties, and Applications of Fluorinated Polyurethane

Fluorinated polyurethane (FPU) is a new kind of polyurethane (PU) material with great applicational potential, which is attributed to its high bond energy C-F bonds. Its unique low surface energy, excellent thermal stability, and chemical stability have attracted considerable research attention. FPU with targeted performance can be precisely synthesized through designing fluorochemicals as hard segments, soft segments, or additives and changes to the production process to satisfy the needs of coatings, clothing textiles, and the aerospace and biomedical industries for materials that are hydrophobic and that are resistant to weathering, heat, and flames and that have good biocompatibility. Here, the synthesis, structure, properties, and applications of FPU are comprehensively reviewed. The aims of this research are to shed light on the design scheme, synthesis method, structure, and properties of FPU synthesized from different kinds of fluorochemicals and their applications in different fields and the prospects for the future development of FPU.

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

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.