Polymer-solvent molecules, polyelectrolyte

If the electrostatic interaction between two like-charged particles is attractive, we call the interaction inverted and if the interaction between oppositely charged particles is repulsive, we also call it inverted. Ionic force inversion is not a denial of Coulomb s law. If it exists, it must be a manifestation of many-body interactions. For example, if two like-charged polymers electrostatically attract each other, it can only be through the mediation of counterions and/or polarizable solvent molecules. Force inversion is a topic currently of widespread interest in polyelectrolyte physics (this volume, Chapter 5). We currently believe that inverted forces can arise through several distinct types of interactions, and it may not always be easy to pick... 

A polyelectrolyte gel (pH-dependent swelling) is immersed in a large solvent reservoir (pure solvent, no added ions). The system consists of three components polymer ions, counter ions, solvent molecules. Each of them contributes to the chemical potential. 

Monte Carlo simulations provide a rewarding and invaluable approach to solving these systems, and computer simulations and theory can isolate the molecular factors that control polyelectrolyte conformations in solution. Therefore, they are exU cmely useful to address the optimization of colloid-polymer mixtures and guide the design of new experiments. A simple model involving one chain interacting with one particle has been described, but the same model can be extended to more concentrated systems, e.g. involving several chains (and/or colloidal particles) with explicit counter ions, co-ions and solvent molecules. 

In a general sense, the swollen polymer films can be considered as a polymer, polyelectrolyte gel [3]. Various microscopic techniques have revealed a pronounced heterogeneity of the surface layer [151-159]. In this respect, one has to distinguish between macropores (whose diameter exceeds 10 nm considerably) and nanopores (which represent solvent molecules and ions between the polymer chains). Inside the macropores, the thermodynamic and transport properties of ions and solvent molecules practically do not differ from that of the contacting bulk solution. The space-charge regions (electric double layers) are formed at the interface between the polymer and solution phases whose thickness is much lower than the characteristic sizes of macroelements (fibrils, grains, and pores). The... 

Basically, the confinement free energy of a polyelectrolyte chain inside a cavity is due to the translational entropy of counterions, electrolyte ions, and solvent molecules. Simple scaling formulas based on the radius of gyration of the polyelectrolyte, analogous to Equations 5.28 and 5.26, are not applicable for the confinement free energy of a polyelectrolyte in spherical cavities, unlike the case of uncharged polymers. 

Usually, the mesoscopic, kinetic models are considered to be well suited for predicting dynamic properties of polymer solutions on macroscopic scales. Details of the fast solvent dynamics are in most cases irrelevant for macroscopic properties. Exceptions are polyelectrolytes, where the motion of counterions in the solvent can have a major influence on polymer conformation. Therefore, more microscopic models of polyelectrolytes with explicit counterions are sometimes employed [34] (see also the contribution by M. Muthukumar in this volume). Another exception is the dynamics of individual biopolymers, for example, protein folding, which is modeled with an all atomistic model including an explicit treatment of the (water) solvent molecules [35]. 

A polymer, large molecules, is made of linked smaller molecules. Firstly, the rubbery properties of rubber trees were discovered by the Mayans. A polyelectrolyte is a macromolecule dissolved in water or polar solvent and gets a large... 

Since the compartmentalization occurs as a result of microphase separation of an amphiphilic polyelectrolyte in aqueous solution, an aqueous system is the only possible object of study. This limitation is a disadvantage from a practical point of view. Our recent studies, however, have shown that this disadvantage can be overcome with a molecular composite of an amphiphilic polyelectrolyte with a surfactant molecule [129], This composite was dissolvable in organic solvents and dopable in polymer film, and the microphase structure was found to remain unchaged in the composite. This finding is important, because it has made it possible to extend the study on photo-systems involving the chromophore compartmentalization to organic solutions and polymer solid systems. 

If 0.6 N lithium bromide is added to the solution of the polyelectrolyte and also to the solvent on the opposite side of the osmometer membrane, the lowermost set of points in Fig. 145 (lower and left scales) is observed. The anion concentration inside and outside the coil is now so similar that there is little tendency for the bromide ions belonging to the polymer to migrate outside the coil. Hence the osmotic pressure behaves normally in the sense that each poly electrolyte molecule contributes essentially only one osmotic unit. The izjc intercept is lower than that for the parent poly-(vinylpyridine) owing to the increase in molecular weight through addition of a molecule of butyl bromide to each unit. 

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