Linkers divinylbenzene

Figure 9 Schematic presentation of the imprinting of (—)-isoproterenol. A self-assembly construct forms between template (—)-isoproterenol (T) and functional monomers (trifluor-methacrylic acid, M) in accordance with the interactions. The basic secondary nitrogen group in the template forms an ionic salt bridge with the strongly acidic monomer the hydroxyl groups form hydrogen bonds with the monomer. This specific assembly is then solidified by copolymerization with a cross-linker (divinylbenzene, L). After pol merization, the template is extracted and the MIP rebinds the imprinted (—)-enantiomer in preference to the (+)-enantiomer.

For example, polymerizing inorganic nanoparticles with cross-linker divinyl-benzene yields composite polymer-inorganic latex particles functionalized with vinyl groups. In the process of composite miniemulsion polymerization, vinyl groups were easily introduced to the particle surface by using cross-linker divinylbenzene, thiol-terminated polymers can be further clicked on the particle surface via a thiol-ene approach catalyzed by V-50 as a free-radical source (Figure 8.27) [48]. 

The organic and aqueous phases are prepared in separate tanks before transferring to the reaction ketde. In the manufacture of a styrenic copolymer, predeterrnined amounts of styrene (1) and divinylbenzene (2) are mixed together in the organic phase tank. Styrene is the principal constituent, and is usually about 90—95 wt % of the formulation. The other 5—10% is DVB. It is required to link chains of linear polystyrene together as polymerization proceeds. DVB is referred to as a cross-linker. Without it, functionalized polystyrene would be much too soluble to perform as an ion-exchange resin. Ethylene—methacrylate [97-90-5] and to a lesser degree trivinylbenzene [1322-23-2] are occasionally used as substitutes for DVB. 

The point at which two polymeric chains are joined together by a cross-linker such as divinylbenzene, or sites where tertiary hydrogens are located in the stmcture, are other locations for oxidative attack. In both cation- and anion-exchange resins, oxidative attack results in the removal of cross-linking. 

Three main types of polymer-based monoliths are polymethacrylate-based monoliths where methacrylate forms the major component of the monomers for polymerization, polyacrylamide-based monoliths where cross-linked polyacrylamide is synthesized directly within the capillary, and polystyrene-based monoliths that are usually prepared from styrene and 4-(chloromethyl) styrene as monomers and divinylbenzene (DVB) as the cross-linker. 

The promethazine imprinted MIP particles were used as the recognition element to fabricate a relevant potentiometric chemosensor [200], These particles, prepared with the vinylbenzene functional monomer and the divinylbenzene cross-linker, effectively bound promethazine as compared to the MIP particles prepared with the MAA or vinylbenzene monomer and the EGDMA cross-linker. The MIP particles were embedded in a PVC membrane attached to one end of a glass tube, which was filled with 1 mM promethazine. The chemosensor was able to detect promethazine potentiometrically with LOD as low as 1.0 x 10-7 M and the dynamic linear concentration range from 5.0 x 10-7 to 1.0 x 10-1 M. With this chemosensor, promethazine concentration can be determined in syrup samples and biological fluids with a response time of 50 s. 

The latexes prepared in the group of Ford [68,69] consisted of hydrophobic monomers and a cross-linker, i.e., styrene, methacrylate monomers with various substitutes in the ester moiety, divinylbenzene, and hydrophilic monomers bearing charged groups, viz., styrylmethyl(trimethyl)ammonium and styrylmethyl(tributyl)ammonium cations. The latexes were catalytically active in reactions of decarboxylation of 6-nitrobenzioxazole-3-carboxylate (Scheme 6) and p-nitrophenyl hexanoate hydrolysis (Scheme 7, n = 6). 

Figure 6 Scaling of alignment. In a lyotropic liquid crystal the alignment is roughly proportional to the concentration of the solid part (A). Stretched gels can be varied by the cross-linker concentration (B) (PS/CDCl3 gel with divinylbenzene (DVB) as cross-linker) or by temperature variation (C). (Reprinted by permission from Macmillan Publisher Ltd. ref. 63, copyright (1998). And reprinted with permission from ref 110. Copyright 2005 American Chemical Society.)...

CM has been reported to provide a synthetic tool for immobilization of reagents. Polymer-supported synthesis with an allylsilyl unit as a linker was developed. Divinylbenzene cross-linked allyldimethylsilylpolystyrene has been reported to undergo highly efficient ruthenium-catalyzed CM with functionalized terminal alkenes (Eq. 45) [78]. Products have been liberated by proto-desilylation with trifluoroacetic acid. 

In this investigation EDMA appears to be a superior cross-linker compared to p-divinylbenzene (p-DVB) or butylene dimethacrylate (BDMA). To evaluate other possible cross-linkers, we tested pure o-, p- and m-DVB and a number of dimetha-... 

Fig. 21.14. Sensitivity pattern to xylenes and ambient humidity (rH) of a non-covalent MIP array PMA (MAA and EDMA) and PSt (styrene and divinylbenzene) with 85 and 70% cross-linker. PMA85/PSt85 is p-xylene and PMA70/PSt70 o-xylene imprinted. Data evaluation is shown in Table 21.2.

The synthesis of cross-linked copolymers of styrene and divinylbenzene has been studied intensively and is well documented. The starting monomer is styrene, and divinylbenzene (DVB) is used as cross-linker. The amount of DVB can reach up to 55 wt.%. At 55% DVB, the copolymer shows practically no swelling and possesses a permanent porosity. Figure 3.21 illustrates the network structure of poly(styrenedivi-nylbenzene) (St-DVB). 

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