Morphology experimental techniques

From a morphological point of view, block copolymer micelles consist of a more or less swollen core resulting from the aggregation of the insoluble blocks surrounded by a corona formed by the soluble blocks, as decribed in Sect. 2.3. Experimental techniques that allow the visualization of the different compartments of block copolymer micelles will be presented in Sect. 2.4. Other techniques allowing micellar MW determination will also be briefly discussed. Micellar dynamics and locking of micellar structures by cross-linking will be commented on in Sects. 2.5 and 2.6, respectively. 

In PNCs, the details of molecular structure and dynamics in the periphery of the nanoparticles (for example, within the lamellar gallery or at the interface) is quite difficult to establish by regular experimental techniques. The inability to monitor the thermodynamics and kinetics of the molecular interactions between the different constituents that determine the structural evolution and final morphology of the materials hinders progress in this field. This is probably the domain where there is an increasing need for computer modeling and simulations. 

The material in this chapter is organized broadly in two segments. The topics on monolayers (e.g., basic definitions, experimental techniques for measurement of surface tension and sur-face-pressure-versus-area isotherms, phase equilibria and morphology of the monolayers, formulation of equation of state, interfacial viscosity, and some standard applications of mono-layers) are presented first in Sections 7.2-7.6. This is followed by the theories and experimental aspects of adsorption (adsorption from solution and Gibbs equation for the relation between... 

In a later study by the Schmidt group (27), electron microscopy was used to characterize morphological changes in microspheres (<0.6 cm in diameter) of Pt, Rh, Pd, and Pt-Rh alloy in a number of reaction environments the reactions were ammonia oxidation, ammonia decomposition, and propane oxidation. No other experimental techniques, such as weight-loss measurements, were employed. After prolonged exposure to reaction mixtures of ammonia and air at temperatures less than 727°C, the surfaces of the spheres were reconstructed to favor specific crystal planes. The structure of the facets was found to be a function of the reaction mixture, temperature, and metal (Fig. 13). In the same reaction mixtures, as well as in pure ammonia at higher temperatures... 

Methods which would produce a surface morphology dependent on the local hardness might, however, be applicable. One such experimental technique uses ultrasonic cavitation to detect hardness differences (18). The sample and an ultrasonic transducer placed near the surface to be studied are immersed in a liquid. 

In many cases, high-temperature modifications of sulfidic compounds cannot be quenched for room temperature examination. Inversion twinnings, crystal morphology, or other crystallographic features may indicate the appearance of polymorphism. Under these circumstances differential thermal analysis (DTA) can be suitable for the determination of the exact phase transition temperatures. DTA determinations are practically valuable if used in conjunction with high-temperature X-ray diffraction methods. DTA apparatus can operate up to 1100 °C and can be specially designed for sulfides2-4) individual experimental techniques are included in these references. 

Experimental techniques commonly used to measure pore size distribution, such as mercury porosimetry or BET analysis (Gregg and Sing, 1982), yield pore size distribution data that are not uniquely related to the pore space morphology. They are generated by interpreting mercury intrusion-extrusion or sorption hysteresis curves on the basis of an equivalent cylindrical pore assumption. To make direct comparison with digitally reconstructed porous media possible, morphology characterization methods based on simulated mercury porosimetry or simulated capillary condensation (Stepanek et al., 1999) should be used. 

One of the key issues of supported model catalysts is to prepare collection of metal particles having a well-defined morphology. Indeed, if a catalytic reaction is structure-sensitive [54], it will depend on the nature of the facets present on the particles. Moreover, the presence of edges, the proportion of which is increasing rapidly below about 5 nm, can affect the reactivity by their intrinsic low coordination and also by their role as boundary between the different facets. In this section I first discuss the theoretical predictions of the shape of small particles and clusters, then I briefly describe the available experimental techniques to study the morphology, and finally I discuss from selected examples how it is possible to understand and control the morphology of supported model catalysts. 

In order to explore the growth dynamics and film morphology, several experimental techniques have been utilized. Experimental techniques utilized to date make use of... 

Experimental Techniques and Surface Morphology of the Non-ideal Ag(lll) Electrodes... 

Approximate ranges of the experimental techniques to study different blend morphologies are summarized in Table 12.15. See also Chapter 8. Morphology of Polymer Blends in this Handbook. 

Table 12.15. Approximate ranges of experimental techniques to study blend morphology of (1) Inter-atomic (2) Molecular, spherulites (3) Eiller aggregates, compatibilized blends (4) Reinforcements, immiscible blends (5) Voids [Utracki, 1989]...

In this review, we shall begin by discussing the experimental techniques which have been used to study either or both of the above two aspects of the problem. Stability criteria will be treated next. Finally, a thorough investigation of the cellular morphology will be given, with particular emphasis on evaporative convection. 

Specific results that have been published include the work of Balasz et. al. who have completed extensive self-consistent calculations and Monte Carlo simulations to evaluate the effect of adding copolymers to a blend on the interfacial tension of the biphase. Additionally, Kramer and others have utilized experimental techniques to determine the mechanism of fracture that occurs at a biphasic interface in the presence or absence of copolymer" - Macosko, however, has viewed the problem from an engineering perspective and has examined the role of added copolymer on the blend morphology that results from typical processing condition. 

Therefore the most convenient way to proceed in order to establish the phase separation mechanism is to use different experimental techniques giving different size scales of the morphology generated, i.e. SAXS and LS [30], or, when possible, to observe the evolution of morphologies by SEM or TEM at the same cure times as LS observations [129]. 

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