Polyelectrolytes chemical species

Surfactant molecules can also be used as anchors for the immobilization of chemical species by noncovalent interactions [38], The hydrophobic part of the molecule interacts with the graphene sheets, whereas the hydrophilic head (charged) can interact with the metal complex by electrostatic interactions or covalent bonding. Polyelectrolytes can also act as spacers for charged chemical species, and in this case, strong electrostatic interactions with carbon materials occur [49,53],... 

Sorci GA, Reed WF. Effect of valence and chemical species of added electrolyte on polyelectrolyte conformations and interactions. Macromolecules 2002 37 554-565. 

Modification of the membranes affects the properties. Cross-linking improves mechanical properties and chemical resistivity. Fixed-charge membranes are formed by incorporating polyelectrolytes into polymer solution and cross-linking after the membrane is precipitated (6), or by substituting ionic species onto the polymer chain (eg, sulfonation). Polymer grafting alters surface properties (7). Enzymes are added to react with permeable species (8—11) and reduce fouling (12,13). 

The polyelectrolyte catalysis of chemical reactions involving ionic species has been the subject of extensive investigations since the pioneering studies of Morawetz et al. [12] and Ise et al. [13-17]. The catalytic effect or the ability of poly-electrolytes to enhance or retard reaction rates is mainly due to concentration or exclusion of either or both of the ionic reactants by the polyions added to the reaction systems. For example, the chemical reaction between ionic species carrying the same charge is enhanced in the presence of polyions carrying the opposite charge. This enhancement can be attributed to an increase in the local concentration... 

Figure 3.1a shows a membrane that is permeable to water and K+ and Cl - ions but impermeable to colloidal electrolytes (polyelectrolytes such as charged proteins). Let a denote the interior of the cell and (3 the extracellular region. In the absence of the poly electrolyte, water, K + and Cl" partition themselves into the two sides such that the chemical potentials of each species are the same inside as well as outside, as thermodynamics would demand. Moreover, the requirement of electroneutrality in both ot and (3 demands that the concentrations of each species K + and CP be the same on either side of the partition. 

Changes in the dimensions of a polyelectrolyte gel may also result from a chemically induced ionization irrespective of isomerization. If this ionization is caused by irradiation with light and if the lifetime of the charged species is sufficiently long to permit the polymer to deform, a mechanophotochemical effect may result . This effect was described by Aviram in the case of poly[p-(N,N-dimethylamino)-N-y-D-glutamanilide] cross-linked with 1.5% 2,6-bis-(bromomethyI)naphthaIene on irradiation in the presence of carbon tetrabromide as an acceptor phoioionization occurs (Eq. (10)). 

Proteins are polymers, more specifically polyelectrolytes, which are discussed in Chapter 6. However, proteins were hardly considered in that chapter because they are highly specific and intricate molecules. They are built of 20 different monomers, with side groups of different reactivity. Proteins evolved to fulfil a wide range of highly specific physiological functions, and each protein has a specific composition and conformation. Every protein species is unique the number of species occurring in nature is presumably far over 1010. Chemical reactivity is at least as important as physical chemistry for protein properties in general and for many problems related to proteins in foods. Despite these qualifications, some important physicochemical rules can be derived, and this is the subject of this chapter. 

Chemical modification by simple copolymerization, for example, creates a new class of polyelectrolyte [20,27-43,129] allowing exploitation of their amphiphilic nature the ability of such polymers to form macromolecular aggregates with a micellar-type structure has been recognized [28,33,128] and their capacity to solubilize organic species in aqueous media [31,32,38,40,44] is of importance in consideration of potential applications which range from controlled release of materials [165,181-183] to photochemical conversion and storage [31,32,36,38,39,44,45]. 

A very important monograph outlined the state of knowledge up to 1974, and also noted other associated species which could influence the rates of thermal, photochemical and radiation induced reactions [1]. The initial studies of micellar effects were made in water, but subsequently micelle-like aggregates were observed in non-aqueous solution. These aggregates can also influence chemical reactivity. In some respects the effects of micelles on reactivity are similar to those of cyclo-dextrins or synthetic polyelectrolytes. 

Another type of functional nanocontainers can be fabricated by Layer-by-Layer assembly of oppositely charged species. Layer-by-Layer assembly of oppositely charged species was first proposed by Iler in 1966 [1] and later developed by Decher et al. [2]. The universal character of the method does not have any restriction on the type of the charged species employed for a shell construction. The precision of one adsorbed layer thickness is about 1 nm. The shell of the polyelectrolyte capsules is semipermeable and sensitive to a variety of physical and chemical conditions of the surrounding media, which might dramatically influence the structure of polyelectrolyte complexes and the permeability of the capsules. Introduction of nanosized metals (Ag, Au) or magnetic nanomaterials (Fe3O4) into the shell of polyelectrolyte capsules attains... 

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