Atomic force microscopy molecule types

Another example of a Pc-based 1-D polymer is that reported by Armstrong and co-workers [158], They prepared a Pc with eight styrene-type polymerizable sites at the end of the peripheral substituents. This molecule forms highly ordered, rod-like aggregates at the air-water interface that can be transferred onto solid supports. Irradiation of the thin films affords polymerization between the olefin moieties of adjacent molecules by photostimulated [2 + 2] cycloaddition. The rod-like Pc macromolecules were conveniently studied by matrix-assisted laser desorp-tion/ionization (MALDI-TOF) spectrometry and atomic force microscopy (ATM), the latter showing rods with lengths up to 290 nm. 

Various types of electron microscopy (TEM, transmission electron microscopy SEM, scanning electron microscopy) and atomic force microscopy (AFM) as well as a host of other spectroscopic techniques (XANES, Auger, LEED, EELS, PES, surface IR, ETV, solid state NMR, etc) give information about the surface structures of solids and also about the state of molecules adsorbed at the surface. 

Atomic force microscopy makes it possible to calculate the adhesion forces between different interfaces. In this type of experiment, both the sample and the tip of a force microscope are coated with a functionalized monolayer. The measurements of force vs distance between the two surfaces allows one to estimate the strength of attractive interactions (if any) between them. Crooks and coworkers obtained the following energy values for H-bond interactions NH2 vs NH2 1.3, COOH vs COOH 5 and COOH vs NH2 16 kcalmol-1. Although adsorbed water molecules may have affected these data, they scale well with those expected for H-bond and acid-base interactions412. 

Basically two different types of experimental approaches have been used to study the boundary shp local (direct) [45,60] and effective (indirect) methods [49-52,61]. The first group of methods is based on apphcation of optical techniques using tracer particles or molecules to determine the flow field. These techniques have a resolution of less than lOOnm, so they cannot distinguish small differences in slip lengths. The effective methods assume the boundary conditions (Eq. 18) or similar ones to hold at the substrate surface and infer the slip length by measuring macroscopic quantities. These methods have been the most popular so far and they include atomic force microscopy (AFM), surface force apparatus (SEA), capillary techniques, and QCM. 

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