Atomic Force Microscopy for Teaching Polymer Crystals and Polymer Blends

The essential component of expanding an undergraduate curriculum is the inclusion of lab experiments in nanoscience and nanomaterials, which significantly impact health and the environment through their use in food, cosmetics, agriculture, and medicine. We designed a laboratory experiment based on the atomic force microscopy (AFM) analysis of the physical characteristics of polymer blends and crystals, including surface morphology, Young's modulus, deformation, and stiffness. The laboratory exercise exposes students to the main aspects of the crystallization of polyethylene glycol and the formation of an immiscible polystyrene/polybutadiene blend, followed by optical microscopy and AFM characterization. In addition to providing information about the surface morphology and microstructure of the samples through AFM topography scanning, nanoindentation measurements allow for the mechanical characterization of materials with nanoscale resolution. Mechanical characterization offers students a broader application area where they can use their chemical understanding to regulate the material's physical characteristics. AFM force curve mapping enables assessment of the components' distribution in composite materials while analyzing each constituent independently with nanoscale precision. The versatility of AFM considerably increases the number of laboratory experiments that can be developed in undergraduate courses on nanoscience and nanomaterials. The knowledge acquired about polymer blending, crystallization, and their characterization at the nanoscale equips students with practical and transferable skills that they may apply in other chemistry and engineering classes to address real-world issues.