Crystalline and Glassy Systems

The relation between bulk modulus and volume has been widely investigated in both crystalline and glassy systems (Anderson and Soga, 1967 Osaka et al., 1985). From the Bom-Meyer potential,... 

An investigation on chemical compositions of crystalline and glassy substances of the NaP03-Na2Si03 and the NaP03 Si02 systems has been carried out by Ohashi and Oshima (37). 

Figure 9.28 Hypothetical isothermal diagram for a binary system A + B showing the amounts of crystalline and glassy phases. (According to [II] with permission of Elsevier Science Publ.)...

Signal from the border of crystallites and glass can be influenced by both crystalline and glassy phases. Thus, the size of crystallites shown in the multi-elemental maps is more or less different from the real one. The determination of the real size of a crystallite is affected by space resolution of the mapping system. However, the distributions of all detected elements are clear enough to show us the information about their fractionation behaviors after the nuclear glass thermal... 

In a perfect crystal at 0 K all atoms are ordered in a regular uniform way and the translational symmetry is therefore perfect. The entropy is thus zero. In order to become perfectly crystalline at absolute zero, the system in question must be able to explore its entire phase space the system must be in internal thermodynamic equilibrium. Thus the third law of thermodynamics does not apply to substances that are not in internal thermodynamic equilibrium, such as glasses and glassy crystals. Such non-ergodic states do have a finite entropy at the absolute zero, called zero-point entropy or residual entropy at 0 K. 

Pharmaceutical solids can generally be described as crystalline or amorphous (or glassy). In fact, the actual solid phase composition of a pharmaceutical formulation is usually characterized by an intermediate composition, both crystalline and amorphous in character. In a multicomponent system, such as a solid formulation comprising drug and excipient(s), certain components or even a single component may be... 

As we have seen in Section 6.6.1 such confined liquids may behave quite differently from the bulk lubricant. Near the surfaces, the formation of layered structures can lead to an oscillatory density profile (see Fig. 6.12). When these layered structures start to overlap, the confined liquid may undergo a phase transition to a crystalline or glassy state, as observed in surface force apparatus experiments [471,497-500], This is correlated with a strong increase in viscosity. Shearing of such solidified films, may lead to stick-slip motions. When a critical shear strength is exceeded, the film liquefies. The system relaxes by relative movement of the surfaces and the lubricant solidifies again. 

Before applying the ideas summarised in the first section to polymer latices it is appropriate to consider the nature of polymer latex particles. We know, for example, that each particle is composed of a large number of polymer chains, with the chains having molecular weights in the range of about 105 to 107. Moreover, the particles themselves can be amorphous, crystalline, rubbery, glassy or monomer swollen, either extensively or minutely. It follows, therefore, that the properties of the system on drying depends directly on the physical state of the particles, for example, if the particles are soft, coalescence can occur to form a continuous film, whereas with hard particles their individuality is retained. The nature of the particle obtained is directly related to the preparative method employed and the surface properties are often determined by s-... 

In Section 1.6.2 we assumed that the temperature is high enough to consider the van der Waals interaction between chains to be small, so the chains (not to consider chemical crosslinks) can move freely beside each other. To complete the picture, we will shortly describe the structure and behaviour of the systems, described in Section 1.6.2, at lower temperatures. In contrast to the previous cases, interchain interaction is not small, so that the mobility of the macromolecule is very severely restricted by neighbouring macromolecules. One can observe, instead of a fluid state, a crystalline and/or glassy state in this case (Ferry 1980). 

The character of the polymethyl methacrylate data is essentially similar to that found for systems atactic polystyrene-benzene at 25°, 35°, and 50° C. [Kishimoto, Fujita, Odani, Kurata and Tamura (1960) Odani, Kida, Kurata and Tamura (1961)] and also atactic polystyrene-methyl ethyl ketone at 25° C. [Odani, Hayashi and Tamura (1961)], and appears to be fairly general for amorphous polymer-solvent systems in the glassy state. On the other hand, the cellulose nitrate data shown in Fig. 8 appear to manifest features characteristic of crystalline polymer-solvent systems. For example, the earlier data of Newns (1956) on the system regenerated cellulose-water (in this case, water is not the solvent but merely a swelling-agent) and recent studies for several crystalline polymers all show essentially similar characters [see Kishimoto, Fujita, Odani, Kurata and Tamura (I960)]. To arrive at a more definite conclusion, however, more extensive experimental data are needed. 

---