Ethylene dimethacrylate

Continuous porous polymer rods have been prepared by an in situ polymerization within the confines of a chromatographic column. The column is filled with glycidyl methacrylate and ethylene dimethacrylate monomer mixtures, cyclo-hexanol and dodecanol diluents, and AIBN initiator. They are then purged with nitrogen, stopped, and closed with a silicon rubber septum. The polymerization is allowed to proceed for 6 hr at 70°C with the column acting as a mold (47). 

The mixture of deprotected amino acid derivatives in solution was then immobilized onto a polymeric solid support, typically activated 5-)xm macroporous poly(hydroxyethyl methacrylate-co-ethylene dimethacrylate) beads, to afford the chiral stationary phases with a multiplicity of selectors. Although the use of columns... 

Divinyl monomers such as divinylbenzene, divinyl adipate, and ethylene dimethacrylate, in which the reaction of one double bond does not alter greatly the reactivity of the other, polymerize to highly cross-linked structures. 

Figure 3. Time dependence of the fraction R of unreacted aminostyrene residues during acetylation by 0.14 M acetic anhydride at 30°C. Methyl methacrylate copolymer in acetonitrile solution (0) linear poly-(methyl methacrylate-co-butyl methacrylate) swollen with acetonitrile Cd) methyl methacrylate copolymer crosslinked with 1 mole% ( ) and with 15 mole% ( ) ethylene dimethacrylate poly(methacrylate crosslinked with 3 mole% ethylene dimethacrylate containing entrapped poly(methyl acrylate-co-aminostyrene) ( ).

It is of much interest to compare polymer monoliths with monolithic silica columns for practical purposes of column selection. Methacrylate-based polymer monoliths have been evaluated extensively in comparison with silica monoliths (Moravcova et al., 2004). The methacrylate-based capillary columns were prepared from butyl methacrylate, ethylene dimethacrylate, in a porogenic mixture of water, 1-propanol, and 1,4-butanediol, and compared with commercial silica particulate and monolithic columns (Chromolith Performance). 

A rather limited range of mesopores in terms of size and volume were observed in the skeletons of polymer monoliths. The porosity of the polymer monolith seems to be lower than that of silica monolith. The total porosity of these monoliths is in the range of 0.61-0.73, whereas interstitial (through-pore) porosity and mesopore porosity are 0.28-0.70 and 0.03-0.24, respectively. In the case of poly(butyl methacrylate-co-ethylene dimethacrylate), the observed porosity is around 0.61-0.71, resulting in permeability 0.15-8.43 x 10 14 m2, whereas the observed porosity of silica monoliths prepared in a capillary is 0.86-0.96 and the permeability is 7-120 x 10 14 m2. Higher permeability will be advantageous for 2D applications, as mentioned later. 

Remarkably, the use of a fluorous biphasic solvent system in combination with a [Rh(NBD)(DPPE)]+-type catalyst (NBD = norbornadiene) copolymerized into a porous nonfluorous ethylene dimethacrylate polymer, resulted in an increased activity of the catalyst relative to a situation when only toluene was used as solvent [30]. The results were explained by assuming that fluorophobicity of the substrate (methyl-trans-cinnamate) leads to a relatively higher local substrate concentration inside the cavities of the polymer when the fluorous solvent is used. That is, the polymer could be viewed as a better solvent than the fluorous solvent system. This interpretation was supported by the observations that (i) the increase in activity correlates linearly with the volume fraction of fluorous solvent (PFMCH) and (ii) the porous ethylene dimethacrylate polymer by itself lowers the concentration of decane in PFMCH from 75 mM to 50 mM, corresponding to a 600 mM local concentration of decane in the polymer. Gas to liquid mass transport limitation of dihydrogen could be mled out as a possible cause. 

This technology was extended to the preparation of chiral capillary columns [ 138 -141 ]. For example, enantioselective columns were prepared using a simple copolymerization of mixtures of O-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydro quinidine, ethylene dimethacrylate, and 2-hydroxyethyl methacrylate in the presence of mixture of cyclohexanol and 1-dodecanol as porogenic solvents. The porous properties of the monolithic columns can easily be controlled through changes in the composition of this binary solvent. Very high column efficiencies of 250,000 plates/m and good selectivities were achieved for the separations of numerous enantiomers [140]. 

Fig. 3. Effect of dodecanol in the porogenic solvent on the differential pore size distribution of molded poly(glycidyl methacrylate-co-ethylene dimethacrylate) monoliths (Reprinted with permission from [62]. Copyright 1996 American Chemical Society). Conditions polymerization time 24 h, temperature 70 °C, polymerization mixture glycidyl methacrylate 24%, ethylene dimethacrylate 16%, cyclohexanol and dodecanol contents in mixtures 60/0 (curve 1), 57/3 (curve 2), 54/6 (curve 3), and 45/15 vol.% (4)...

Fig. 6. Reaction of poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolith with diethylamine...

Fig. 8. Effect of linear flow velocity of an L-benzoyl arginine ethylester solution (0.2 mol/1) on the enzymatic activity of trypsin immobilized on poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads (curve 1) and monolith (curve 2) (Reprinted with permission from [90]. Copyright 1996 Wiley-VCH). Reactor 50 mm x 8 mm i.d., temperature 25 °C...

Table 1. Porous properties and enzymatic activities of monolithic poly(2-vinyl-4,4-dimethyl-azlactone-co-acrylamide-co-ethylene dimethacrylate) reactors3... 

Conditions polymerization mixture 20 wt% ethylene dimethacrylate, 20% vinyl azlac-tone+acrylamide, 60% porogenic solvent, and azobisisobutyronitrile (1% with respect to monomers), temperature 65 °C polymerization time 24 h. b Percentage of vinyl azlactone (VAL) and acrylamide (AA) in polymerization mixture. c Median of the pore size distribution profile. d Total pore volume. 

The postmodification strategy, in which apoly(glycydyl methacrylate-co-ethylene dimethacrylate) monolith was activated with hydrogen sulfide to a thiol-modified monolith and subsequently derivatized with an 0-9-(tert-butylcarbamoyl)quinine selector by radical addition reaction, yielded slightly less efficient capillary columns. However, this procedure has the advantage that only minute amount of chiral selector are needed to end-up with a useful enantioselective capillary column [84]. 

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