2, Keysight Technologies, Santa Clara, California, United States
A development of fast imaging for most atomic force microscopy (AFM) applications is a current trend of this technique. We illustrate the potential of combining fast imaging and variable temperature studies, which were performed on samples of mesomorphic polymer – poly(diethylsiloxane) – PDES, of semicrystalline polyethylenes of different type and bitumen. Quick Scan in scanning probe microscopes of Keysight Technologies is based on use of the fast-response piezo nose-cone embedded into a regular scanner and high-frequency probes with 1st flexural resonance around 1.5 MHz. In variable temperature experiments the imaging of surfaces at scales from hundreds of nanometers to a hundred of mm with scanning rates up to 50 Hz allows fast recording of morphological transformations and nanoscale structures in a time of milliseconds. Quick Scan provides not only the substantial time savings in experiments, but also enables recording of structural changes at heating rates of 5-10 degrees/min, which are common for other characterization techniques such as differential scanning calorimetry (DSC), dynamic mechanical analysis, etc. Structural changes can be visualized practically at every temperature degree, and this capability empowers comprehensive material characterization. The data, which were recorded on PDES samples prepared in different ways, have confirmed a coexistence of several crystalline, mesomorphic and isotropic states of this polymer. Crystallization from different mesomorphic states proceeds in different path for samples with various thermal histories. Transition from crystalline to mesomorphic order took place in a broad temperature range compared to crystallization. In rubbed sample mesomorphic order has originated from isotropic state at oriented strips of material serving as the nuclei. Newly grown lamellar aggregates are more extended compared to those formed by rubbing. In variable temperature experiments on polyethylene samples we have obtained novel results regarding crystallization, melting and related structural transformations in samples with different crystallinity and chain order. Particularly, we have monitored crystallization process and recorded kinetic data in study of polyethylene based on ethylene/octene copolymer. These results can be obtained with high time efficiency that is invaluable in industrial research environment. Other technologically important material – bitumen has been examined in the temperature range from +90C to -20C with Quick Scan. These studies have revealed specifics of wax crystallization and a formation of surface wrinkling in different shapes depending on thermal history and cooling rate from melt. This technique has a strong potential for a more thorough examination of composition and thermal behavior of bitumen. The demonstrated successful use of Quick Scan at different temperatures is only one of many areas of AFM applications that strongly benefit from this advanced technique.