Silicate melts polymer models

In polymeric models for silicate melts, it is postulated that, at each composition, for given values of P and T, the melt is characterized by an equilibrium distribution of several ionic species of oxygen, metal cations, and ionic polymers of monomeric units SiOt. ... 

Hess P. C. (1971). Polymer models of silicate melts. Geochim. Cosmochim. Acta, 35 289-306. 

There is thus good experimental evidence that silicate melts are ionic liquids containing relatively free cations and mixtures of polymeric silicate anions. In a previous chapter Kleppa has reviewed what is known of the mixing properties of simple molten salts. The applications of these principles to melts containing a large number of different polyanions requires the introduction of methods developed by organic polymer chemists (Flory, 1936, 1952). Before describing the polymer models which have been applied to silicate melts it will be useful to review briefly the use of the terms acidic and basic as applied to oxides or melts. 

The activity-composition curves shown in Fig. 7 may be interpreted if a suitable reaction model involving the basic oxide is available. Since silicate melts appear to contain large numbers of different molecular species, reaction models have been developed which are based on the concepts of organic polymer theory. Two such models will be described below ... 

Polymer models of the type described above have been used with considerable success to interpret the mixing properties of certain binary silicate melts. Althoiagh the polymerization constants for melts of geological complexity are as yet unknown and the... 

R. A. Vaia, E. P. Giannelis, Polymer melt intercalation in organically-modified layered silicates Model predictions and experiment, Macromolecules, vol. 30, pp. 8000-8009, 1997. 

Polymer silicate nanocomposites offer unique possibilities as model systems to study confined polymers or polymer brushes. The main advantages of these systems are (a) the structure and dynamics of nanoconfined polymer chains can be conveniently probed by conventional analytical techniques (such as scattering, DSC, NMR, dielectric spectroscopy, melt rheology) (b) a wide range of different polymers can be inserted in the interlayer or end-grafted to the silicate... 

On a global scale, the linear viscoelastic behavior of the polymer chains in the nanocomposites, as detected by conventional rheometry, is dramatically altered when the chains are tethered to the surface of the silicate or are in close proximity to the silicate layers as in intercalated nanocomposites. Some of these systems show close analogies to other intrinsically anisotropic materials such as block copolymers and smectic liquid crystalline polymers and provide model systems to understand the dynamics of polymer brushes. Finally, the polymer melt-brushes exhibit intriguing non-linear viscoelastic behavior, which shows strainhardening with a characteric critical strain amplitude that is only a function of the interlayer distance. These results provide complementary information to that obtained for solution brushes using the SFA, and are attributed to chain stretching associated with the space-filling requirements of a melt brush. 

V aia, R. A. Giannelis, E.P. Lattice model of polymer melt intercalation in organically-modified layered silicates. Macromolecules 1997,30, 7990-7999. 

The one step process for the fabrication of pure silica sliver from sodium silicate [1-3] is an adaptation oil the generic dry spinning process that has been practiced for over 50 years in the fabrication of polymer organic textile fibers. Acrylic polymers, unlike polyesters or nylons, are infusible and cannot be melt spun. They can be dry or wet spun from viscous solutions. The model for inorganic dry spinning processes is the dry spinning process by means of which acrylic fibers such as Orion, are spun using dimethyl formamide as the solvent (Table I). 

Vaia, R. A. Giannelis, E. P., Lattice Model of Polymer Melt Intercalation in Organically-Modified Layered Silicates. Macromolecules 1997, 30, 7990-7999. Vaia, R. A. Giannelis, E. P., Polymer Melt Intercalation in Organically-Modified Layered Silicates Model Predictions and Experiment. Macromolecules 1997, 30, 8000-8009. 

Vaia, R.A. Giannelis, E.P. Polymer melt intercalation in organically-modified layered silicates Model predictions and experiment. Macromolecules 1997, 30, 8000-8009. Equation (2.2) in this chapter differs from equation (6) in Ref. 26. Private discussions with R.A. Vaia clarified that Equation (2.2) as provided here is correct, and is the same as the authors used for their calculations in Refs. 26 and 25. Equation (6) in Ref. 26 was wrongly put in press due to a typographical error. 

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