Polystyrene macroporous

The capacity of studied organopolymeric sorbents depends on metal nature (Pd (II) > Au (III) > Pt (IV)) as well as on the composition and stmcture of sorbent matrix (polyvinylpyridine macroporous > polystyrene macroporous > polystyrene fibrous). 

A macroporous polystyrene-divinylbenzene copolymer is produced by a suspension polymerization of a mixture of monomers in the presence of water as a precipitant. This is substantially immiscible with the monomer mixture but is solubilized with a monomer mixture by micelle-forming mechanisms in the presence of the surfactant sodium bis(2-ethylhexylsulfosuccinate) (22). The porosity of percentage void volume of macroporous resin particles is related to percentage weight of the composite (50% precipitant, 50% solvent) in the monomer mixture. 

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). 

Monosized macroporous polystyrene-divinylbenzene particles have been prepared in a multistep swelling process, in which particles of different sizes... 

Removal of diluent by an extraction process To obtain the final stable macroporous structure, the liquid organic diluents and the linear polymer are removed from the crosslinked structure by extraction with a good solvent for the inert diluents and particularly for the linear polymer. Toluene or methylene chloride are usually preferred for the removal of linear polystyrene from the divinylbenzene crosslinked macroporous polystyrene particles [125,128]. The extraction is carried out within a Soxhelet apparatus at the boiling point of the selected solvent over a period usually more than 24 h. 

A typical scanning electron micrograph of the uniform macroporous polystyrene-divinylbenzene particles is given in Fig. 20. First studies on the synthesis of macroporous uniform particles were started by Ugelstad et al. [109]. They used a two-step activated swelling method to obtain macroporous uniform particles in the... 

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. 

Buerge et al. [8] PCMs (AHTN and HHCB) Wastewater effluent Switzerland - Macroporous polystyrene-divinylbenzene adsorbent - Silica gel chromatography - GC-MS - Recovery=81-141% LOD=10 ng/L... 

Preparation of 2-unsubstituted products by this method would require the use of formaldehyde as the aldehyde component, which gives low yields. However, the use of glyoxylic acid, either as the free acid or bound to macroporous polystyrene carbonate, results in satisfactory formation of the 2-unsubstituted products through an in situ decarboxylation <2004OL4989>. The use of a nonpolar solvent (toluene) has been reported to reduce the formation of side products in this type of reaction <2006TL947>. 

Hulme et al. describes the novel use of ethyl glyoxalate in the Ugi-4CR to create ketopiperazines [31]. iV-alkylated/Boc-protected ethylene diamines 60 reacted with an isocyanide 61, a carboxylic acid 62, and ethyl 2-oxoacetate 63 in stoichiometric ratio of 1/1/1/1.25 in methanol. Deprotection and cyclization is completed using TFA and MP-carbonate (a macroporous polystyrene... 

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 first attempts to use macroporous polystyrene supports for onium ion catalysts were reported in the early papers of Brown and Jenkins 54) and of Regen 89). The lightly cross-linked macroporous Rohm and Haas XE-305, 46 % RS as spacer chain catalyst 15, gave O- and C-alkyl products from 2-naphthoxide ion and benzyl bromide... 

Cross-linked polystyrene tolerates well a broad range of reaction conditions, including treatment with weak oxidants (ozone, DDQ), strong bases (LDA), and acids (HBr, TfOH). Saponifications with 40% aqueous sodium hydroxide at 180 °C for 10 h can be realized on 5% cross-linked macroporous polystyrene without deterioration of the polymer [36]. Not surprisingly, however, strong oxidants at high temperatures, and other reagents which lead to a chemical modification of alkylbenzenes, will attack polystyrene. 

The fact that macroporous, highly cross-linked polystyrene does not swell makes this support particularly interesting for continuous-flow synthesis in columns. This support has also been successfully used as an alternative to CPG for the solid-phase synthesis of oligonucleotides [90,91]. Furthermore, because reagents do not need to penetrate into the polystyrene network, enzyme-mediated reactions should also proceed smoothly on macroporous polystyrene [85]. 

Amidines and sulfonamides have also been used as linkers for primary or secondary aliphatic amines (Entries 4, 5, and 7, Table 3.23). These derivatives are stable under basic and acidic reaction conditions and can only be cleaved by strong nucleophiles. Phenylalanine amides can be hydrolyzed by treatment with certain enzymes (Entry 8, Table 3.23), and can therefore be used for linking amines to supports compatible with enzyme-mediated reactions (CPG, some polyacrylamides, macroporous polystyrene, etc.). 

Alkenes can be transformed into ketones by Wacker oxidation (Entry 2, Table 12.3), but this reaction does not seem to proceed cleanly on polymeric supports. Janda and co-workers were able to oxidize styrenes bound to macroporous polystyrene to the corresponding acetophenones, but reported that the reaction did not proceed on PEG... 

Macropolyhedral thiaboranes, preparation, 3, 127 Macroporous polystyrene resins, for metal complex immobilization, 12, 665-666 Macroscale combustion calorimetry, limitations, 1, 611-612... 

Structure Macroporous polystyrene-divinylbenzene nonpolar adsorbent, 62-177 pm particle size Analytical Properties Used mainly in preparative-scale HPLC stable over entire pH range (1-13) sometimes difficult to achieve column-to-column reproducibility due to packing the irregular particles relatively lower efficiency than alkyl bonded phases particles tend to swell as the organic content of the mobile phase increases Reference 1... 

Comparable experiments were performed with DexP-coated macroporous polystyrene-divinylbenzene (PS-DVB) particles [264] and with DexP, labelled with 4-amino-TEMPO, using EPR spectroscopy to study the conformation of the polymer chains [265]. Low substituted DexP gave thicker layers with lower density than highly substituted derivatives due to the presence of more loops and tails. With increasing DS of DexP, the stiffness of the adsorbed layers and, therefore, the density increases and the non-specific interaction of BSA with the DexP-coated PS-DVB surfaces seems to be restricted to the top of the adsorbed layer. 

The first polymer-supported reagents were derived from ion-exchange resins by immobilizing ionic reagents on macroporous polystyrene resins [5], This approach enables easy access to many reagents. For preparation, a... 

An early example for the direct coupling of a tin reagent to Amberlite XE 305, a macroporous polystyrene, was reported by Crosby and coworkers157. The synthetic route is shown in Scheme 35. Reaction of the polymer-supported diorganotin dihydride 70 with iodooctane to give octane indicated a minimum content of 2 mmol tin hydride per gram of the polymer. 

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". 

For the purpose of recycling, some of these strong bases where immobilized on gel-type and macroporous polystyrene. The influence of the morphology on the reactivity was checked a six carbon chain-spacer was introduced between the main chain and the biguanide group. 

Figure 4 Electron Micrographs of Porous Structures of Composite Resins a) Polyhipe Manufactured by Inverse Polymerization b) 20% -Crosslinked Macroporous Polystyrene...

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