Isoporous resin

Negere et al. reported that the condition of isoporosity is dependent on the concentration of polystyrene in the initial solution. Isoporous resins are obtained... 

The structure of the isoporous sulfonic acid resins is as fully accessible for the tetrabutylammonium ions as are the standard resins with 1-2% DVB (Table 4). The isoporous resins irrespective of the type and amount of erosslinking can be completely saturated with the tetrabutylammonium ions. On the contrary, it is well known that the tetrabutylammonium ion uptake of standard SDVB resins fall sharply with the increasing degree of crosslinking. 

Ratio of ion-exchange capacities of Ratio of ion-exchai e capa-isoporous resins towards cities of standard SDVB resins... 

Ratio of ion-exchange capacities isoporous resins towards (C4H9)4N+ and Na+... 

Surprisingly, one carmot find any interesting or useful information from the pubhcations concerning the structure and properties of isoporous resins... 

The chemical nature and morphology of the polymer might affect both the intraparticle diffusion of reactants and the intrinsic reactivity at the active site. The isoporous polystyrene support of Tundo S may be highly active because of faster reactant diffusion in an isoporous matrix than in a conventional divinylbenzene-cross-linked matrix. The isoporous resin retained 9.4 g of dichloromethane per g ot resin compared with 4.4 g of dichloromethane per g of a conventional 2% cross-linked benzyltributylphosphonium catalyst. No information is available on the degree of hydration of the isoporous catalyst. 

Organic traps contain isoporous, macroporous, or other specifically designed resins (such as reticulated, cross-linked polystyrene resins devoid of ionic function) and take up organics by a combination of ion exchange, adsorption, and other mechanisms. They typically are installed to precede the DI plant. 

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. 

T. R. E. Kressmann J. R. Millar Invention and development of isoporous ion-exchange resins. 1960... 

In general, the ion-exchange resins synthesized from the isoporous polymers are characterized by high exchange capacity, high permeability for large organic ions, and low volume fluctuations. 

Table 3. Comparison of ion-exchange capacity of sulfonated isoporous and standard resins...

Such a structure is termed gel-isoporous and does demonstrate a much improved resistance to organic fouling compared with distinctly gel-heteroporous, but otherwise equivalent, resins. Nowadays the term isoporous has largely disappeared by way of the fact that minimizing the degree of heterogeneity of structure is inherent in the production of most modern premium gel anion exchange resins. 

Fig[ure 5.4 Non-exchange electrolyte sorption of NaCl and HCl by styrenk anion and cation exchange resins respectively against external concentration [m = internal molality A = macroporous SB A (low capacity) B = macroporous SBA (conventional) C = isoporous SBA (gel) D = macroporous SAC E = gel SAC]... 

Theoretical advances ongoing Continuous countercurrent practice and development Fixed bed counterflow designs Macroporous, Isoporous, and Acrylic anion resins The Organic Fouling Debate ... 

Belfer et al.157-161) reported that irreversible structural transformations take place during the chloromethylation of isoporous polystyrene resins. A styrene —... 

M. Negre, M. Bartholin and A. Guyot, Autocross-linked isoporous polystyrene resins, Angew. Makromol. Chem., 1979, 80, 19-30 J. Hradil and E. Kralova, Styrene-divinylbenzene copolymers post-cross-linked with tetrachloromethane, Polym., 1998, 39, 6041-6048 S. Belfer and R. Glozman, Anion exchange resins prepared from polystyrene cross-linked via a Friedel-Craft reaction, J. Appl. Polym. Sci., 1979, 24, 2147-2157. 

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