Globular disperse structures

FIGURE 3.17 Models describing 2D (a) and 3D (b) globular disperse structures. (From Shchukin, E.D., Physical-chemical theory of the strength of disperse structures and materials, in Physical-Chemical Mechanics of Natural Disperse Systems, E.D. Shchukin, N.V. Pertsov, V.I. Osipov, and R.I. Zlochevskaya (eds.), Izd. MGU, Moscow, Russia, 1985, pp. 72-90.)... 

This description corresponds to the case of disperse structures of globular type in which the strength originates from a continuous skeleton that forms due to adhesion of individual particles upon the conversion of free disperse system into structured disperse system. There are, however, other types of structures, such as, e.g., cellular structures (in solidified foams and emulsions), in which the skeleton consists of continuous films of solid-like dispersion medium. Such structures, typical for some polymeric systems, may... 

The primary sample structure was oriented with some globular dispersed phase oriented as well in the same direction as the matrix. The dispersed phase was in some places highly birefringent. After incubation of the samples in trypsin solution the oriented structure of the matrix was again observed, but had weaker birefringence. There was observed a slight decay of dispersed phase, probably due to cellulose degradation. 

In Sections 13.3.4 and 15.5.2, we already encountered the role of dispersion interaction in, respectively, globular protein structure and protein adsorption. Here, we discuss dispersion forces in somewhat more detail. 

In systems with solid and liqtrid phases, the elasticity modulus is determined by the interactions between the particles of the dispersed phase. For porous disperse structures of globular type with phase contacts between the particles, the elasticity modulus of the systan is determined by the elasticity modulus of the substance making up the solid phase and by the number and area of the... 

Globular protein (Section 27 20) An approximately spheri cally shaped protein that forms a colloidal dispersion in water Most enzymes are globular proteins Glycogen (Section 25 15) A polysaccharide present in animals that IS denved from glucose Similar in structure to amy lopectin... 

The main contributions to AadsG for a globular protein are from electrostatic, dispersion, and hydrophobic forces and from changes in the structure of the protein molecule. Although in this section these contributions are discussed individually, strict separation of the influence of these forces on the overall adsorption process of a protein is not possible. For instance, adsorption-induced alteration of the protein structure affects the electrostatic and hydrophobic interaction between the protein and the surface. When the sorbent surface is not smooth but is covered with (polymeric)... 

Figure 5 presents the results of tensile tests for the HPC/OSL blends prepared by solvent-casting and extrusion. All of the fabrication methods result in a tremendous increase in modulus up to a lignin content of ca. 15 wt.%. This can be attributed to the Tg elevation of the amorphous HPC/OSL phase leading to increasingly glassy response. Of particular interest is the tensile strength of these materials. As is shown, there is essentially no improvement in this parameter for the solvent cast blends, but a tremendous increase is observed for the injection molded blend. Qualitatively, this behavior is best modeled by the presence of oriented chains, or mesophase superstructure, dispersed in an amorphous matrix comprised of the compatible HPC/OSL component. The presence of this fibrous structure in the injection molded samples is confirmed by SEM analysis of the freeze-fracture surface (Figure 6). This structure is not present in the solvent cast blends, although evidence of globular domains remain in both of these blends appearing somewhat more coalesced in the pyridine cast material.

The overall shape of the protein, long and narrow or globular, is called its tertiary structure and is maintained by several different types of interactions hydrogen bonding, dipole-dipole interactions, ionic bonds, covalent bonds, and London dispersion forces between nonpolar groups. These bonds, which represent all the bonding types discussed in this text, are summarized in Fig. 22.25. 

Polymerization in microemulsion systems has recently gained some attention as a consequence of the numerous studies on microemulsions developed after the 1974 energy crisis (1,2). This new type of polymerization can be considered an extension of the well-known emulsion polymerization process (3). Hicroemulsions are thermodynamically stable and transparent colloidal dispersions, which have the capacity to solubilize large amounts of oil and water. Depending on the different components concentration, microemulsions can adopt various labile structural organizations -globular (w/o or o/w tyne), bicontinuous or even lamellar -Polymerization of monomers has been achieved in these different media (4-18),... 

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