Macroporous polymer resins

A flow synthesis of peptides using a macroporous polymer resin soon followed additionally incorporating an in-line UV detector, which constantly monitored the progress of the reaction by analyzing the output of the column the reaction was recirculated until it reached completion. However, backpressures of500-1000 psi were encountered, making these systems only suitable for metal-encased columns [93],... 

Besides chemically bonded phases on silica gel supports microparticulate macroporous polymer resins also have been used in the analysis of alkaloids (see Chapters 7 and 8). A disadvantage of macroporous polymer resins is that they are not as rigid as the reversed-phase materials based on silica gel. In addition they may shrink or swell slightly - depending on the composition of the mobile phase. On the other hand they are more stable than chemically... 

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 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... 

Hi. The monomer polymerization route. Compared with the resin-functionalization route, the homo- and copolymerization of organotin-containing monomers permits one to influence the polymer resin structure to a greater extent. In principle, it is possible to prepare gel-type, macroporous, microporous or nonporous polymers. The pore structure, tin loading, solubility and other factors which influence the reactivity of the polymer-supported organotin reagents can be controlled by appropriate... 

Our studies on solvent-impregnated resins, consisting of soluble compounds of type IB impregnated onto macroporous polymer carriers, have enabled us to conclude that a hydrophilic or amphiphilic component must be present in the polymeric network, in order to allow for fast ion diffusion inside the polymeric matrix. It is imperative that this component possesses none or minimal metal-ligand properties, so that it will not interfere with the ion selectivity of the main chelating group [6,7]. 

After a brief rinse the retained sample anions are eluted with a solution of 1 M HC1 in methanol. Again, the ion exchange column should be small and the resin should be a macroporous polymer of 1 mequiv/g exchange capacity. 

The single enantiomer of 45 is produced by enantioselective acylation with vinyl acetate catalysed by Novozym 435, an immobilised lipase from Candida antarctica containing about 1% w/w enzyme on a macroporous polypropylic resin. You will appreciate that as both substrate and catalyst are on polymers, one at least must be soluble in the reaction mixture. The polymer is stripped from the substrate 45 with HF. 

Lipases are manufactured by fermentation of selected microorganisms followed by a purification process. The enzymatic interesterification catalysts are prepared by the addition of a solvent such as acetone, ethanol, or methanol to a slurry of an inorganic particulate material in buffered lipase solution. The precipitated enzyme coats the inorganic material, and the lipase-coated particles are recovered by filtration and dried. Various support materials have been used to immobilize lipases. Generally, porous particulate materials with high surface areas are preferred. Typical examples of the support materials are ion-exchange resins, silicas, macroporous polymers, clays, etcetera. Effective support functionality requirements include (i) the lipase must adsorb irreversibly with a suitable structure for functionality, (ii) pore sizes must not restrict reaction rates, (iii) the lipase must not contaminate the finished product, (iv) the lipase must be thermally stable, and (v) the lipase must be economical. The dried particles are almost inactive as interesterification catalyst until hydrated with up to 10% water prior to use. 

Candida antarctica Lipase B (CALB) is atfracting increasing attention as a biocatalyst for the synthesis of low molar mass and polymeric molecules. Almost all publications on immobilized CALB use the commercially available catalyst Novozym 435, which consists of CALB physically adsorbed onto a macroporous acrylic polymer resin (Lewatit VP OC 1600, Bayer). Primarily, commercial uses of CALB are limited to production of high-priced specialty chemicals because of the high cost of commercially available CALB preparations Novozym 435 (Novozymes A/S) and Chirazyme (Roche Molecular Biochemicals). Studies to better correlate enzyme activity to support parameters will lead to improved catalysts that have acceptable price-performance characteristics for an expanded range of industrial processes. 

Comparing the values of the distribution constant (Kd) for DTMPPA and DEHPA for Amberlite XAD-2 and for organic solvents, we note that the distribution equilibria of DTMPPA and DEHPA shift more to the resin phase and it seems that the interaction of DTMPPA and DEHPA with the resin phase acts to drive the displacement of the extractant molecules further from solution and toward the macroporous polymer. As expected, the pKj value of DTMPPA and DEHPA obtained from the distribution data on XAD-2 and toluene is similar to that obtained for DTMPPA dissolved in organic solvents [18,41], as can be seen in Table 2. 

This book contains 17 chapters and is divided into 3 parts. Chapters 1-5 deal with the more fundamental aspects of known types of polystyrene networks, like type of networks, the formation of macroporous polymers, the preparation of continuous polymeric beds and the properties of ion-exchange resins, among other examples. 

Solvent porogen effects for macroporous resins are often explained in terms of the degree of solvation imparted to the incipient polymer netwoik, the point at which phase separation takes place, and the resultant degree of in filling between primary particles [26]. This may play a role in some amorphous MOPs (for example, micro/ mesoporous PPV [13]) however other systems such as HCPs (Sect. 2.1) do not undergo phase separation in this way [21, 22]. This basic mechanistic difference also accounts for the apparent independence of surface area on monomer concentration for conjugated microporous PAE networks [ 19], for example, in comparison with macro-porous polymer resins where surface area may be strongly concentration dependent. 

Reuse of the phosphine resins for Wittig reactions has been reported without details several times. In the only detailed results 92% conversion of phosphine oxide to phosphine with trichlorosilane was attained with a 2% cross-linked polymer, and repeated synthesis of stilbene by quatemization with benzyl bromide and Wittig reaction with benzaldehyde gave 97% gc yields in both the second and the third cycles based on the amount of phosphonium bromide used (H). Identical recycling of a 20% cross-linked macroporous polymer gave 75% gc yield of stilbene compared with 80% from the first use (131. 

A styrene/divinylbenzene copolymer was phosphorylated and converted to a polymer with phenylphosphinic acid groups 41 [114] (see Experiment 5-9, Section 5.4). Ion-exchange coordination to Cu(II), Cd(II), Ni(II), Zn(II) and Eu(III) was studied. Resins with carboxylic groups in the a- and P-positions display higher metal ion uptake than those with -COOH in the y-position. Macroporous polymers 42 with a functional group based on triisobutyl-phosphine sulfide have been synthesized and characterized for the selective adsorption of Au(III) and Pd(II) [115]. 

The spectrum of commercial adsorbents for use in air pollution control also includes beaded, hydrophobic adsorber resins consisting of nonpolar, macroporous polymers produced for the specific application by polymerizing styrene in the presence of a crosslinking agent. Crosslinked styrene divinylbenzene resins are available on the market under different trade names. Their structure-inherent fast kinetics offers the advantage of relatively low desorption temperatures. They are insoluble in water, acids, lye and a large number of organic solvents. 

---