Structure of Ion-exchange Resins

The most common formulation of ion-exchange resins is polystyrene cross-linked with divinylbenzene. The conventional styrene-divinylbenzene copolymer forms colorless transparent particles and consists of a homogeneous polymer phase. By changing the divinylbenzene content, one can modify the three dimesional networks of the copolymers. These resins are called gel-type copolymers. 

The macroreticular resins are prepared by copolymerizing styrene and divinylbenzene in the presence of an organic compound that is a good solvent for the monomer but a poor swelling agent for the polymer. They form opaque round particles and have large surface areas. 

Various functional groups are introduced to the copolymers to form the cation or anion exchange resins. For example, the sulfonation of benzene nuclei with sulfuric acid yields cation-exchange resins of strong acidity. 

Resins of weak acidity are obtained by introducing carboxy groups. Resins of strong basicity are obtained by introducing quaternary ammonium groups to the copolymer. The characteristics of some styrene-divinylbenzene ion exchange resins are listed in Table 3.37. 

The cation exchange resins can be used up to 390 and 420 K for the gel types and the macroreticular types, respectively. The anion exchange resins can be used up to 343-370 K. 

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Scheme 2.1. Structures of ion exchange resin (a) cation and (b) anion.

The basic chemical structure of ion exchangers is the same for most of them. They are quite often formed by PS-DVB cross-linked frameworks, with different kind and degree of functionalization, cross-linking degree, specific surface area and porosity. The large-scale industrial production of PS-DVB resins started more than 50 years ago [40]. The ready availability of these materials attracted the attention of chemists interested into chemical synthesis... 

The presence of insoluble materials in the polymerization mixture may have some control on the structure of the polymeric skeleton. Seidl et al. reported that the micro structure of skeletons of ion-exchange resins, based on the copolymers of styrene and DVB, can be controlled by carrying out the polymerization in presence of an inert material and by adjusting the reaction conditions and concentration of DVB. The micro structure depends on the parameter of interaction and on the molar volume of the inert material. In the case of copolymers modified by an inert component with high molar volume and interaction parameters, microstructures with small measureable surfaces and pores with relatively large radii are obtained. 

INFLUENCE OF POLYMERIC MATRIX STRUCTURE ON PERFORMANCE OF ION-EXCHANGE RESINS V. A. Davankov, S. V. Rogozhin, and M. P. Tsyurupa... 

Use Molding, adhesives, laminating, textile finishes, permanent-press fabrics, wash-and-wear apparel fabrics, protective coatings, paper manufacture, leather treatment, binders for fabrics, foundry sands, graphite resistors, plaster-of-paris fortification, foam structures, and ion-exchange resins. 

In 1960, Hirs, Moore, Stein, and Anfinsen described the first primary structure of the enzyme ribonuclease (M.W. 13,700), which has a single peptide chain of 124 amino acid residues and four intrachain disulfide bonds. These investigators established many of the techniques still used in sequence analysis, such as the use of ion exchange resins for separation of peptides and amino acids. 

This third edition is essentially an entirely new book. Our goal has been to describe the materials, principles and methods of ion chromatography in a clear, concise style. Whenever possible the consequences of varying experimental conditions have been considered. For example, the effects of the polymer structure and the chemical structure of ion-exchange groups and the physical form of the ion-exchange group attachment on resin selectivity and performance are discussed in Chapter 3. 

Esterification of glycerol with oleic acid in the presence of ion exchange resins. Influence of the resin structure. 

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