Polymer association complexes, water

Dried samples of up to 4 layers of self-assembled polyelectrolytes on silica particles have been investigated by solid state NMR techniques [82] IH MAS spectra at 30 kHz rotation showed the signals of residual water molecules associated with the polyelectrolyte, while no signal of the polymer was detected. By comparison to spectra of dried polymer bulk complexes water sites associated with the silica surface and the multilayers, respectively. 

On the basis of the above experimental results, the expected conformations of polymer-surfactant complexes at the oil-water interface are depicted in Fig. 2.19. In case I, the added polymer associates with excess surfactants present in the bulk solution, but the complexes prefer to remain in the bulk phase. Alternately, the polymer-surfactant complexes are unable to displace the adsorbed surfactant molecules from the liquid-liquid interface. Irrespective of the amount of polymer-surfactant concentration in the bulk, the experimental decay length values remain comparable to the Debye lengths, corresponding to the concentration of ion species in the bulk solution (Eq. (2.11)). This means that the force profile is... 

When a water-soluble polymer is dissolved in water, a complex network is formed that includes the polymer backbone, free water, and water in various degrees of bonding to the polymer. Depending on the concentration of polymer, its molecular weight, and several other factors, the network of polymer and bound water can assume the volume of the solution. This, of course, leads to the high viscosity that these solutions develop. The volume occupied by the polymer and the associated water in the system are said to be the hydrodynamic volume. As this volume increases because of increases in molecular weight or in the water shell surrounding the molecule, the viscosity of the solution increases. 

We have studied polymer association in solution both by the increase in the energy transfer between donor and acceptor labels of interacting species and by use of the medium-sensitive "dansyl label. This chromophore fluoresces strongly in organic media but very weakly in water solution. Thus, when dansyl-labeled polyiacrylic acid) associates in aqueous solution with POE or PVP, water is displaced from the microenvironment of the label and the emission intensity increases sharply. This phenomenon allowed us to study the extent and the nature of such associations. This technique can also be used to follow the kinetics of complex interchange and with the use of a stopped-flow apparatus the much faster complex formation can also be studied . 

As the discussion above implies, there are several different types of enzymatic attack on solid polymers. The simplest case in concept is attack on the polymer by a soluble, freely diffusing, extracellular enzyme which degrades the polymer to form water soluble, low molecular weight fragments that dissolve and diffuse through the aqueous environment until they are taken up by the microorganisms that produced and secreted the depolymerase enzyme. A more complex case is that in which the enzyme is associated with or bound to the outer wall or cell surface of the microorganism, which must attach itself to the polymer surface to permit the immobilized enzyme to seek out the section of the polymer... 

A Ithough it is the most abundant of the metallic elements in the outer crust of the earth, aluminum usually occurs in natural waters in concentrations below 100 micrograms per liter. High concentrations occur rarely and usually are associated with water having a low pH. The chemical properties of aluminum which control its behavior in water have been studied extensively. This paper is based on current research by the U.S. Geological Survey and on published literature. The principal topics considered here are the processes by which aluminum combines with hydroxide ions to form complexes and polymers, the influence of these processes on solubility of aluminum and the forms of dissolved species to be expected in natural water, and the relative importance of fluoride and sulfate complexes of aluminum. The experimental work is briefly summarized here. Details are published elsewhere (6). 

It is difficult to trace the historical development of the theory of water. One of the earliest documents attempting an explanation of some anomalous properties of water is Rontgen s (1892) article, which postulated that liquid water consists of two kinds of molecules, one of which is referred to as an ice-molecule. Rontgen himself admitted that his explanation of the properties of water, using the so-called mixture-model approach, had been known in the literature for some time, but he could not point out its originator. An interesting review of the theories of water until 1927 was presented by Chad well (1927). Most of the earlier theories were concerned with association complexes, or polymers of water molecules. There has been little discussion on the structural features of these polymers. 

Fig. 6.12 Sequential hydrogen bonds formed along the polymer chain due to cooperative hydration. The type of polymer-water associated complex is specified by the index j = (71,72, ), where is...

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