Sulfonated cross-linked

Early recommendations for cross-linking CSM involved the use of divalent metal oxides to form metal sulfonate cross-links (24). The mechanism involves the hydrolysis of the sulfonyl chloride group with a carboxyHc acid, ie, stearic acid, which produces water at curing temperatures. 

Chromatographic System Use a liquid chromatograph equipped with a refractive index detector that is maintained at a constant temperature and a 9-mm x 30-cm column packed with a strong cation-exchange resin, about 9 pm in diameter, consisting of sulfonated cross-linked styrene-divinylbenzene copolymer in the calcium form (Aminex HPX-87c, or equivalent). Maintain the column temperature at 85° + 0.5°, and the flow rate of the Mobile Phase at about 0.5 mL/min. Chromatograph the Standard Preparation, and record the peak responses as directed under Procedure. Replicate injections show a relative standard deviation not greater than 2.0%. 

To overcome such limitations, Imura et al. covered the surface of a silica gel with sulfonated cross-linked polystyrene [5]. After adsorption of styrene, divinyl-benzene, and r-butyl peroxide and subsequent free-radical polymerization, the acid groups are introduced via classical sulfonation. Control of the thickness of the crosslinked polymer layer on the surface is essential to prevent pore clogging. This sulfonated polystyrene-Si02 hybrid material preserves a large specific surface area, with a typical ion-exchange capacity of 1.8 meq g. Alternatively, a sulfonated layer can be deposited on silica by copolymerization of silica-supported methacrylate and potassium p-styrene sulfonate [6]. 

Determination of the ion-exchange capacity The exchange capacity is determined as described above for sulfonated cross-linked polystyrene. 

The sulfonated cross-linked polystyrene resins have been by far the most popular materials for the separation of inorganic species, including the actinides. Typical of these is Dowex-50. This resin is usually specified as "X 4" or "X 12," etc., which means 4% or 12%, etc. divinylbenzene was added to the styrene in the... 

In some cases, the polysiloxane was in the form of a composite—for example, with sulfonated cross-linked polystyrene particles, carbon black,acrylate latexes,or sodium dodecyl sulfate. Counterintuitively, the addition of impenetrable nanofillers can actually increase the permeability of a membrane. Also, siloxane-imide copolymers have shown some interesting properties in membrane separations, as have polysiloxanes containing poly(ether amine) groups. ... 

We have found that in sensors based on this simple homopolymer, the mediator, FcC, leaches finm the internal solution into the analyte solution. In order to mitigate this problem, the films were subsequently cross-linked and sulfonated. Cross-linking was accomplished by exposing the film to a 5 % (v/v) solution of trichloromethylsilane, in ethanol. Sulfonation was accomplished by exposing the film to a 2 % (v/v) solution of 2-(4-... 

Figure I.6a also reveals the timeline of milestones in fuel cell design. The leftmost curve is the performance curve of the first practical H2/O2 fuel cell, built by Mond and Langer in 1889 (Mond and Langer, 1889). The electrodes consisted of thin porous leafs of Pt covered with Pt black particles with sizes of 0.1 lam. The electrol)de was a porous ceramic material, earthenware, that was soaked in sulfuric acid. The Pt loading was 2 mg cm and the current density achieved was about 0.02 A cm at a fuel cell voltage of 0.6 V. The next curve in Figure I.6a marks the birth of the PEFC, conceived by Grubb and Niedrach (Grubb and Niedrach, 1960). In this cell, a sulfonated cross-linked polystyrene membrane served as gas separator and proton conductor. However, the proton conductivity of the polystyrene PEM was too low and the membrane lifetime was too short for a wider use of this cell. It needed the invention of a new class of polymer electrolytes in the form of Nafion PFSA-type PEMs to overcome these limitations.

J. Chen, M. Asano, T. Yamaki and M. Yoshida, Preparation of sulfonated cross-linked PTFE-gra/l-poly(alkyl vinyl ether) membranes for polymer electrolyte membrane fuel cells by radiation processing, J. Membr. Sci. 256, 38 (2005). 

Macronet ion-exchangers were prepared by treatment of styrene-acrylonitrile copolymer and polystyrene foam with chlorosulfonic acid. The reaction involved simultaneous sulfonation and the formation of sulfone cross-links. - ... 

DVS-C-PBI-7 = divinyl sulfone cross- linked PBI containing 7% degree of cross-linking ... 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

Cross-linked macromolecular gels have been prepared by Eriedel-Crafts cross-linking of polystyrene with a dihaloaromatic compound, or Eriedel-Crafts cross-linking of styrene—chloroalkyl styrene copolymers. These polymers in their sulfonated form have found use as thermal stabilizers, especially for use in drilling fluids (193). Cross-linking polymers with good heat resistance were also prepared by Eriedel-Crafts reaction of diacid haUdes with haloaryl ethers (194). 

Sulfonated styrene—divinylbensene cross-linked polymers have been appHed in many of the previously mentioned reactions and also in the acylation of thiophene with acetic anhydride and acetyl chloride (209). Resins of this type (Dowex 50, Amherljte IR-112, and Permutit Q) are particularly effective catalysts in the alkylation of phenols with olefins (such as propylene, isobutylene, diisobutylene), alkyl haUdes, and alcohols (210) (see Ion exchange). Superacids. 

EPDM-Derived Ionomers. Another type of ionomer containing sulfonate, as opposed to carboxyl anions, has been obtained by sulfonating ethylene—propjlene—diene (EPDM) mbbers (59,60). Due to the strength of the cross-link, these polymers are not inherently melt-processible, but the addition of other metal salts such as zinc stearate introduces thermoplastic behavior (61,62). These interesting polymers are classified as thermoplastic elastomers (see ELASTOLffiRS,SYNTHETIC-THERMOPLASTICELASTOLffiRS). 

Copolymers of sodium acrylate with sodium 2-acrylamido-2-methylpropane sulfonate (AMPS) or /V, /V- dim ethyl acryl am i de (52) have been used to prepare cross-linked systems at high temperatures and salinity. Chromium cross-linked gels, prepared from a 3 1 blend of partially hydrolyzed... 

Surfactants evaluated in surfactant-enhanced alkaline flooding include internal olefin sulfonates (259,261), linear alkyl xylene sulfonates (262), petroleum sulfonates (262), alcohol ethoxysulfates (258,261,263), and alcohol ethoxylates/anionic surfactants (257). Water-thickening polymers, either xanthan or polyacrylamide, can reduce injected fluid mobiHty in alkaline flooding (264) and surfactant-enhanced alkaline flooding (259,263). The combined use of alkah, surfactant, and water-thickening polymer has been termed the alkaH—surfactant—polymer (ASP) process. Cross-linked polymers have been used to increase volumetric sweep efficiency of surfactant—polymer—alkaline agent formulations (265). 

Combination techniques such as microscopy—ftir and pyrolysis—ir have helped solve some particularly difficult separations and complex identifications. Microscopy—ftir has been used to determine the composition of copolymer fibers (22) polyacrylonitrile, methyl acrylate, and a dye-receptive organic sulfonate trimer have been identified in acryHc fiber. Both normal and grazing angle modes can be used to identify components (23). Pyrolysis—ir has been used to study polymer decomposition (24) and to determine the degree of cross-linking of sulfonated divinylbenzene—styrene copolymer (25) and ethylene or propylene levels and ratios in ethylene—propylene copolymers (26). 

The monomer 4-styrenesulfonic acid was prepared by dehydrohalogenation of -bromoethjibenzene—sulfonyl chloride. The potassium salt can be polymerized in aqueous solution (222). The sulfonation of cross-linked polystyrene beads is being carried out in industry with concentrated sulfuric acid. 

Sulfonated polyalkenes were prepared by using a triethyl phosphate—sulfur trioxide complex as the sulfonating reagent along with a solvent at low temperature. Sulfonation takes place at the a-position of the double bond with no cross-linking (222). 

Modification of the membranes affects the properties. Cross-linking improves mechanical properties and chemical resistivity. Fixed-charge membranes are formed by incorporating polyelectrolytes into polymer solution and cross-linking after the membrane is precipitated (6), or by substituting ionic species onto the polymer chain (eg, sulfonation). Polymer grafting alters surface properties (7). Enzymes are added to react with permeable species (8—11) and reduce fouling (12,13). 

Poly(vinyl alcohol) is readily cross-linked with low molecular weight dialdehydes such as glutaraldehyde or glyoxal (163). Alkanol sulfonic acid and poly(vinyl alcohol) yield a sulfonic acid-modified product (164). 

Solvent Recovery. A mixture of methanol and methyl acetate is obtained after saponification. The methyl acetate can be sold as a solvent or converted back into acetic acid and methanol using a cationic-exchange resin such as a cross-linked styrene—sulfonic acid gel (273—276). The methyl acetate and methanol mixture is separated by extractive distillation using water or ethylene glycol (277—281). Water is preferred if the methyl acetate is to be hydroly2ed to acetic acid. The resulting acetic acid solution is concentrated by extraction or a2eotropic distillation. 

The resins used are highly cross-linked organic polymers with acidic functional groups. The most common of the resins used are sulfonated copolymers of styrene and divinylben2ene (see Ion exchange). 

Some commercial durable antistatic finishes have been Hsted in Table 3 (98). Early patents suggest that amino resins (qv) can impart both antisHp and antistatic properties to nylon, acryUc, and polyester fabrics. CycHc polyurethanes, water-soluble amine salts cross-linked with styrene, and water-soluble amine salts of sulfonated polystyrene have been claimed to confer durable antistatic protection. Later patents included dibydroxyethyl sulfone [2580-77-0] hydroxyalkylated cellulose or starch, poly(vinyl alcohol) [9002-86-2] cross-linked with dimethylolethylene urea, chlorotria2ine derivatives, and epoxy-based products. Other patents claim the use of various acryUc polymers and copolymers. Essentially, durable antistats are polyelectrolytes, and the majority of usehil products involve variations of cross-linked polyamines containing polyethoxy segments (92,99—101). 

---