Atomic force microscopy phase transition

In this part we will present the power of atomic force microscopy (AFM) for the nanoscale investigations of the solid-isotropic liquid crystal interfaces. The work described here is focused on direct measurements of forces between solid objects, immersed in an isotropic liquid ciystal that is close to the phase transition to an ordered liquid crystalline phase. Solid surfaces induce some liquid crystalline order in the surrounding liquid crystal and this influences the force between the objects. Consequently, it is possible to extract important information about the behaviour of the liquid crystalhne order in the few nanometer thick interfacial layer by studying the forces. 

In this section experimental results are discussed, concerned with analyses of melting and crystallization kinetics, as well as reversibility of the phase transition. The frame of the discussion is set by Fig. 3.76, which will be supported by experimental data on poly(oxyethylene). The thermal analysis tools involved are TMDSC, optical and atomic-force microscopy, DSC, adiabatic calorimetry, and dilatometry. Most of these techniques are described in more detail in Chap. 4. Results from isothermal crystallization, and reorganization are attempted to be fitted to the Avrami equation. This is followed by a short remark on crystallization regimes and finally some data are presented on the polymerization and crystallization of trioxane crystals. 

Godovsky, Y. K. Papkov, V. S. Magonov, S. N., Atomic Force Microscopy Visualization of Morphology Changes Resulting from the Phase Transitions in Poly(di-n-alkoxysiloxane)s Poly(diethylsiloxane). Macromolecules 2001,34, 976-990. 

Abstract Surface-induced ordering of 4-n-octyl-4 -cyanobiphenyl (8CB) near the isotropic-nematic phase transition was investigated using temperature-controlled atomic force microscopy (AIM). The glass surfaces in contact with liquid crystal were modified by an adsorbed silane surfactant, a deposited 8CB mono-layer, or a deposited 8CB trilayer. 

Boussard and Tao [41,42] used atomic force microscopy (AFM) to study cast and self-assembled, adsorbed DDAB layers on highly ordered PG (HOPG) electrodes. Consistent with Figure 4, theirresults suggested that Mb inserts into the DDAB bilayers. A potential-driven phase transition of adsorbed DDAB was observed by AFM, which may cause physical movement of the DDAB microstructures close to the electrode and possibly assist in mass transport of Mb during CV scans. 

Mechanical properties of a polymer blend change as a function of temperature, particularly near phase transitions. Normally, the modulus and damping of a blend are recorded for the entire sample. Here, we present atomic force microscopy results from local measurements of the individual components of a polymer blend. The data are collected either as images at a set temperature, or spectra of a small area on the surface as a function of temperature. 

ILs may transition from liquid to solid or mesophase due to possible strong interactions between ILs and inorganic mineral surfaces. Much evidence, " including our previous work, has demonstrated the coexistence of liquid and solid phases of ionic liquids [BmimjlPFs] on mica surfaces at room temperature using atomic force microscopy (AFM). Although it has previously been found that some liquids e.g., water) become ordered or solid-like in the layers adjacent to the surface of crystallized solid substrates, the solid layer of [Bmimj Fe] found on mica surfaces is much more stable. 

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