Polystyrene, macroporous, beads

The first type of polymer we studied was macroporous polystyrene beads functionalised with potassium sulphonate groups.17 Macroporous beads were used because they are particularly easily to separate. The functionalised beads were used to "fish" in a pool of commercial crown ethers. Whilst some of the crown ethers bound to the beads, unfortunately it appeared that many were just simply adsorbed. The second type of polymer studied, in an otherwise similar system, was gel-type beads. These have no inner surfaces for adsorbtion. However, even here adsorbtion appeared to be a problem.17 It was concluded from these early studies that it would be better to use a soluble polymer as the "fishing rod". 

The most extensively used macroporous resins are polystyrene-based ion-exchange resins. They are made of poly(styrene-co-divinylbenzene) with subsequent modification to arylsulphonic acids, quaternary ammonium salts or other derivatives mainly located on the internal surface of the pores [33,34]. This renders them accessible to munerous organic solvents including water and alcohols. Recently, these ion-exchange resins have had a revival for the immo-biUsation of ionic reagents [31,32] in automated synthesis. Macroporous beads have also been used for the immobihsation of catalysts [5,7] however, leach-... 

Figure 21. Schematic of the bis(dithiocarbamate) ligand derived from A-sulfonyletylene diamine anchored on macroporous polystyrene-divinylbenzene beads.

Copper(n) bis(dithiocarbamate) groups have been bound to macroporous polystyrene resins (139,1763) and other polymeric sorbents (1764), with ESR spectroscopy being used to detected and probe the nature of the copper environment. The A -sulfonylethylene bis(dithiocarbamate) ligand when anchored on macroporous polystyrene-divinylbenzene beads has been used for the selective removal of mercury(II), silver(I), and copper(II) from aqueous solutions, the overall selectivity being... 

A macroporous polystyrene-divinylbenzene copolymer, produced by copolymerizing a mixture of styrene and divinylbenzene, is dissolved in an organic liquid such as t-amyl alcohol or isooctane, which is a solvent for monomers. This solvent is unable to substantially swell the resulting copolymer. Macroporous cation-exchange beads are also produced from these macroporous copolymers (25,26). 

Macroporous resin beads, due to their mode of preparation, consist of a macroporous internal structure and highly cross-linked areas (>5%). The latter impart the resin with rigidity, whereas the porous areas provide a large internal surface for functionalization, even in the dry state. These macroporous polystyrene-based resins are subsequently modified in various manners, which render them compatible with numerous organic solvents. Furthermore, they show high resistance toward osmotic shock, but can be brittle when not manipulated carefully. 

New polymeric solid supports have been devised, which include macroporous styrene-divinylbenzene containing large fixed pores, porous glass beads, insoluble carbohydrate polymers, poly(ethylene oxide), cross-linked derivatives of polyacrylamide resins, and graft copolymers of polystyrene and poly(ethylene oxide). The last two have been the most effective and widely used and have competed well with the original copoly(styrene-divi-nylbenzene) beads. 

Macroporous and isoporous polystyrene supports have been used for onium ion catalysts in attempts to overcome intraparticle diffusional limitations on catalyst activity. A macroporous polymer may be defined as one which retains significant porosity in the dry state68-71 . The terms macroporous and macroreticular are synonomous in this review. Macroreticular is the term used by the Rohm and Haas Company to describe macroporous ion exchange resins and adsorbents 108). The terms microporous and gel have been used for cross-linked polymers which have no macropores. Both terms can be confusing. The micropores are the solvent-filled spaces between polymer chains in a swollen network. They have dimensions of one or a few molecular diameters. When swollen by solvent a macroporous polymer has both solvent-filled macropores and micropores created by the solvent within the network. A gel is defined as a solvent-swollen polymer network. It is a macroscopic solid, since it does not flow, and a microscopic liquid, since the solvent molecules and polymer chains are mobile within the network. Thus a solvent-swollen macroporous polymer is also microporous and is a gel. Non-macroporous is a better term for the polymers usually called microporous or gels. A sample of 200/400 mesh spherical non-macroporous polystyrene beads has a surface area of about 0.1 m2/g. Macroporous polystyrenes can have surface areas up to 1000 m2/g. 

The acidity of these resins, however, increases significantly by treating them with Lewis acid halides. Gates and co-workers151 153 have prepared a superacid catalyst from AICI3 and beads of macroporous, sulfonated polystyrene-divinylbenzene. The... 

Polystyrene beads (PS) are employed as physical templates for macropore. The emulsifier-tee emulsion polymerization method used here allows for the synthesise of nearly monodisperse latex beads of PS in the size of ca. 100 nm [10]. PS beads were prepared using 700 ml degassed water, 54 ml styrene monomer, 0.65 g potassium persulhite as initiator, and 20 ml divinylbenzene as cross-linkmg agent. PS beads were obtained at 70°C and 350 rpm, and dried under ambient condition. Aluminum fec-butoxide and stearic acid were separately dissolved in parent alcohol,. rec-butyl alcohol, at room tempature, and then the two solutions were mixed. Appropriate amount of HNO solution was dropped into the mixture at a rate of I ml/min to acidify and hydrolyze the aluminum precursor. PS beads were added into aluminum hydroxide solution after stirring for 10 h. The final pH of the reactant was approximately 7. Organic templates, both stearic acid and PS bead, were easily removed tern dried aluminum hydroxide by calcination. The overall synthetic procedure is as shown in Fig. 1. 

As with MTBE, acidic resins are the catalysts employed in the industrial practice for ETBE synthesis standard products, made from different manufacturers in the form of spherical beads (e.g., Rohm and Haas, Bayer, Purolite, Dow), have similar characteristics - a macroporous structure, polystyrene-divinylbenzene, functionalized with sulfonic groups (active sites 5.2 eq H per kg). 

Three-dimensionally ordered macroporous ceramic with high LR ion conductivity was prepared by colloidal crystal templating method using monodispersed polystyrene beads [12]. Monodispersed polystyrene beads with 3 pm diameter were dispersed in water and then filtrated by using a membrane filter under a small pressure difference. After this treatment, polystyrene beads were accumulated on the membrane filter with closed pack structure, as shown in Fig. 4.2. Then, the membrane consisting of accumulated polystyrene beads was removed from the membrane filter and put on a glass substrate. After drying at room temperature, the... 

Fig. 4.13 Preparation process of three-dimensionally ordered macroporous carbon with controlled pore size distribution by using monodispersed polystyrene and silica beads...

Macroporous resins are compatible with organic, aqueous, protic and aprotic media. They have low swelling characteristics, making the resin ideal for use in fixed bed applications. Stratospheres and QuadraPure are widely used macroporous based resins. The QuadraPure consists of functionalized macroporous polystyrene beads (Figure 9.7). 

The potential of grafted polymers remained unrecognized until the use of PS-PTFE support was resurrected in the 1990s under the phosphoramidite method [168]. The aminomethylated and loaded with nucleoside 3 -succinate from 12.5 to 48pmol per g-PS-Teflon support has been employed successfully in the automated synthesis of oligodeoxyribonucleotides as long 143-mer, with stepwise efficiency of up to 99.8%, comparing favorably with such popular carriers as silica beads CPG-500 and macroporous polystyrene Primer Support (Pharmacia). 

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