Polystyrene microporous

As far as polymer supports for microwave-assisted SPOS are concerned, the use of cross-linked macroporous or microporous polystyrene (PS) resins has been most prevalent. In contrast to common belief, which states that the use of polystyrene resins limits reaction conditions to temperatures below 130 °C [14], it has been shown that these resins can withstand microwave irradiation for short periods of time, such as 20-30 min, even at 200 °C in solvents such as l-methyl-2-pyrrolidone or 1,2-dichlorobenzene [15]. Standard polystyrene Merrifield resin shows thermal stability up to 220 °C without any degradation of the macromolecular structure of the polymer backbone, which allows reactions to be performed even at significantly elevated temperatures. 

Most polymeric redox reagents have been developed on microporous polystyrene, typically cross-linked with 1% divinylbenzene. Few examples have been reported for macroporous polystyrene, silica or other supports such as high-loaded cross-linked polyethylene imine (Ultraresins). Some problems specific for redox reactions can also arise from the reactivity of the polymer support itself. In cross-linked polystyrene, for example, benzylic positions can be oxidized at elevated temperatures and thus can account for a competing reaction pathway [8], Further reactivities are found for other solid supports as well. 

Telford, S., P. Schlunt, and P. C. Chau, Mechanisms of Polymer-Supported Phase Transfer Catalysis. Effect of Phase Ratios on Low Percent Ring Substitution Microporous Polystyrene Resin, Macr-mol., 19, 2455(1986). 

The bromine-lithium exchange reaction on macroreticular PS-resins using nBuLi in THE could be driven to completion by repetitive lithiation as described by Frechet. The lithiation of highly loaded microporous resins, however, were successfully carried out in toluene or benzene. The direct lithiation reaction of microporous polystyrene-derived resins (2% DVB) using nBuLi in cyclohexane in the presence of TMEDA is much faster than that of macroreticular resins (20% DVB).l It is interesting to note that for this reaction THE and benzene are not the solvents of choice. Using cyclohexane as solvent allows the synthesis of resins with a low or medium degree... 

KaUva M, Armatas GS, Vamvakaki M (2012) Microporous polystyrene particles for selective carbon dioxide capture. Langmuir 28 2690-2695... 

Dionex currently offers two ion-ejodusion columns lonPac ICE-ASl and AS6. The former is a moderately hydrophilic, microporous polystyrene/divinylben-zene-based cation exchanger with a particle diameter of 7.5 pm and an ion-exchange capacity of 27 mequiv/column, functionalized with srdfonate groups. The lonPac ICE-ASl is primarily used for the separation of weak inorganic adds, aliphatic monocarboxylic adds, and alcohols. Difficulties are encountered, however, in the separation of ahphatic di- and tri carboxylic adds. These acids elute from such stationary phases within the totally permeated volume. The selectivity of the separation in this retention range is usually very poor. Since the totally... 

Tomoi found that the rate of reaction of 1-bromooctarle with aqueous sodium cyanide increased markedly as the catalyst particle size decreased. (See Figure 2). It is fortunate that mo t investigators of active site structure and percent ring substitution effects on catalysis have confined their attention to a single batch of polymer beads, usually 200/400 mesh microporous polystyrene obtained commercially. Comparisons of activites of structurally different catalysts are valid only if the same particle size and mixing method are used. Consequently activities of catalysts studied in different laboratories are usually impossible to compare reliably. 

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