Polymers solvation theoretical studies

Experimental as well as theoretical methods have been widely employed to study such phenomena as solubility, the conformational structures, size change, and so on. Although these methods have been very successful, however, for example the experimental methods cannot reveal the detailed solvation structures to describe the interaction between solvent and polymer. Either theoretical methods are also not completely atomistic or they assume a certain molecular behavior. Molecular simulation methods, on the other hand, can produce most atomistic information about the solvation process. In this section we will mostly focus on the application of molecular dynamics simulation technique to understand solvation process in polymers. 

One of the most important phenomena in the polymer solvation is the change in the overall size of the polymer chain upon solvation. In fact at equilibrium the average size of isolated polymer molecules in solution is a function of solvent quality and varies from expanded conformations in good solvents to random walk conformations in poor solvents. This is referred to as collapse transition and was first predicted by Stockmayer [82] more than 45 years ago. The phenomenon was observed by Nishio et al. [83] and Swislow et al. [84] more than 25 years ago and is still a subject of much experimental, computational, and theoretical research today. So far many investigators have tried to study the chain size with solvation using a variety of methods. 

Booy ML (1963) Influence of Channel Curvature on Flow, Pressure Distribution and Power Requirements of Screw Pumps and Melt Extmders, Soc Plastics Engrs Trans., 3 pp 176. Cameiro OS, Covas JA et al (2000) Experimental and theoretical study of twin-screw extrasion of polypropylene. J Appl Polym Sci 78(7) 1419-1430 Che D, KotipaUi U et al (2010) Atorvastatin calcium propylene glycol solvates, USPTO Crowley MM, Zhang F et al (2007) Pharmaceutical applications of hot-melt extrusion part I. Drug Dev Ind Pharm 33(9) 909-926... 

Several experimental studies indicate the existence of a short-ranging repulsive interaction that cannot be explained by DLVO theory or by the presence of polymers and micelles. Since it is observed in particular for hydrophilic surfaces and polar solvents, its origin is traditionally attributed to the solvation of the smface and is called solvation or hydration interaction. However, the experimental findings seem partly contradictory and the theoretical explanations are manifold. Hydration interactions are reported for different materials, e.g. latex (e.g. Healy et al.l978). 

The ability of vibrational spectroscopy (infrared and Raman) to probe the different interactions which take place in a solution is well known. From the classic reviews by Irish and Brooker [1] and Gardiner [2], both published in 1977, which cover the Raman spectroscopy of ionic interactions in aqueous and nonaqueous solutions, a number of works have appeared reviewing vibrational spectroscopic studies [3-13]. However, many of these embrace only partial aspects or they are exclusively devoted to one specific type of solution (aqueous or nonaqueous) and do not include topics that will be discussed in the present chapter, such as solutions at high pressures and temperatures, electrolyte polymers, or solutions in the glassy state. The aims of this review are, as its title indicates, the ion-ion interactions whose theoretical aspects have been recently approached in a comprehensive monograph by Barthel and co-workers [14]. This means that aspects related to the Raman spectroscopic studies of the solvent s structure or the interactions between the solute and the solvent (ion hydration or, in general, solvation) will be treated briefly. 

Construction of theoretical phase diagrams similar to the diagram in Fig. 2.17 should facilitate the search for major proaches to the analysis of polymer-solvent systems in which equilibria involving isotropic, liquid-crystalline, crystal solvate, and truly crystalline phases are complexly associated. This is valid, since, as indicated in the classic course of statistical thermodynamics of van der Waals and Konstamm [45], physicists and chemists do not need the precise quantitative dependence for the concrete case as much as to establish general types and then to study whether the qualitative differences of these types coincide with the experimentally found types. ... 

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