Polystyrene, isoporous

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. 

By a method similar to isoporous polystyrene synthesis, poly(4-vinylpyridine) has been cross-linked with dibromoalkanes to give insoluble networks containing pyri-dinium ions (26)113). 

The isoporous macrocrosslinked networks are obtained by the introduction of crosshnking bridges on polystyrene or slightly crosslinked polystyrene... 

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

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. 

Preparation of Macronet Isoporous and Hypercrosslinked Polystyrene Networks... 

At the same time, crosslinking of polystyrene chains in solution or in swollen state is expected to lead to a homogeneous distribution of links, that is, to materials referred to as isoporous (see Chapter 5). 

SYNTHESIS OF MACRONET ISOPOROUS AND HYPERCROSSLINKED POLYSTYRENE NETWORKS... 

Synthesis conditions of macronet isoporous and hypercrosslinked polystyrene networks... 

Table 16.1 Ion exchange capacity (meq/g) of the macronet isoporous hypercrosslinked, and conventional sulfonates of polystyrene [369]...

Figure 16.1 Water uptake as a function of the crosslinking degree of macronet isoporous and hypercrosslinked sulfonates based on (1-3) linear polystyrene, styrene copolymers with (4) 0.8 and (5) 1% DVB, and crosslinked with (1, 5)...

The term isoporous has been used by Davankov29 to describe polystyrenes cross-linked by Friedel-Crafts alkylation because they are claimed to swell extensively even in nonsolvents. Tundo s isoporous catalyst was highly swellable.23 xts activity probably should be compared with those of 0,5% or 1% divinylbenzene-cross-linked catalysts. Such lightly cross-linked polystyrenes generally are not physically stable enough under conditions of use for large scale manufacturing processes. The physical stability of isoporous catalysts has not been repbrted. 

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