Styrene-divinylbenzene copolymers porosity

S 11. — — Ion exchange resin matrices. IV. Densities and porosity of ion exchange matrices on the basis of styrene-divinylbenzene copolymers. Chem. prtimysl 13, 100 (1963). 

The porogen is usually an inert solvent, or mixtures of inert solvent and polymers. The meso- and macropores in the polymer network are the voids once occupied by the porogen. Individual recipes for the preparation of macroporous polymer beads may seem complex in terms of the number of components involved and the required control of the experimental conditions. The technology, however, for their preparation has been developed to such a degree that excellent control over their properties (e.g. particle size, shape, porosity and chemistry) is routinely achieved. The vast majority of current macroporous polymers are based on styrene-divinylbenzene copolymers. Other suitable monomers include acrylates, methacrylates, hydroxyalkylacrylates, vinylpyridines and vinyl acetate. A wide range of products are available for HPLC in particle sizes from 5-20 p,m, pore diameters from about 2-400 nm, and surface areas from about 50-500 m /g [141,144,146-148]. 

Sederel, W.L. DeJong, G.J. Styrene-divinylbenzene copolymers. Construction of porosity in styrene-divinylbenzene matrixes. J. Appl. Polym. Sci. 1973, 17, 2835-2846. 

Ion Exchange Resins As Chromatographic Supports. A versatile type of support is one which can exhibit differential ion exclusion, size exclusion, ion complexing, and hydrophobic interaction characteristics with respect to a variety of molecules. In fact, a generic support of this type exists, and is based on a copolymer of sulfonated styrene-divinylbenzene (DVB). Sulfona-tion impacts the ability of the support to complex counter-ions which, in turn, can complex with the solute or exclude an ionic species. The degree of resin cross-linking is proportional to DVB content and determines effective porosity of the resin and size exclusion characteristics. 

The most commonly used polymeric support is a copolymer styrene/divinylbenzene functionalized with various reactive groups such as chloromethyl (Merrifield resin) and various spacers such as ethylene glycol (Wang-type resin). The supports now available vary one from another in many aspects and properties functionalization, cross-linking, porosity, loading, bead size. All these variations generate different swelling behaviours, different hydrophilicity, and different chemical stability. 

Producing a polystyrene (PS)-DVB copolymer of increasing porosity has been accomplished by dissolving 50-80% styrene, 10-50% divinylbenzene, and 30-70% of an inert organic liquid. Toluene is a solvent for the monomer but is a nonsolvent for the polymerized polymer. The monomer solution is then incorporated into water to form a dispersion of oil droplets followed by the polymerization of the suspended oil droplets from the aqueous medium into the polymer (21). 

The synthesis of cross-linked copolymers of styrene and divinylbenzene has been studied intensively and is well documented. The starting monomer is styrene, and divinylbenzene (DVB) is used as cross-linker. The amount of DVB can reach up to 55 wt.%. At 55% DVB, the copolymer shows practically no swelling and possesses a permanent porosity. Figure 3.21 illustrates the network structure of poly(styrenedivi-nylbenzene) (St-DVB). 

B. N. Kolarz, Ion Exchangers XIX. Some Properties of the Carboxylic Cation Exchangers Obtained by Intermesh Polymerization of Methacrylic Acid into Styrene and Divinylbenzene Porous Copolymers, /. Polym. Sci. 47C, 197 (1974). PS/PMA IPNs. Both polymers crosslinked with DVB. Effect of porosity of network I. Effect of crosslink density of network I. Ion exchange properties. 

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