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Polymer Monoliths (polymer + monolith)
Kinds of Polymer Monoliths Selected AbstractsHigh-performance separation of small inorganic anions on a methacrylate-based polymer monolith grafted with [2(methacryloyloxy)ethyl] trimethylammonium chlorideJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009Damian Connolly Abstract A glycidyl methacrylate- co -ethylene dimethacrylate monolith in capillary format (100 ,m/id) has been grafted with chains of poly([2(methacryloyloxy)ethyl] trimethylammonium chloride (poly-META) and applied to the ion-chromatographic separation of selected inorganic anions. Grafting chains of META onto the generic monolithic scaffold resulted in a monolith with ,electrolyte responsive flow permeability', which manifested as increased permeability in the presence of electrolyte solutions. Using an eluent of 2 mM sodium benzoate and on-column contactless conductivity detection, a test mixture of six common anions was isocratically separated and detected within 12 min, with the first four anions baseline resolved within a retention time window of 3.2 min. Retention time precision was ,1.2% for all anions tested. Separation efficiencies of 15 000 N/m were achieved for fluoride at 1 ,L/min, with column efficiencies up to 29 500 N/m obtained at a lower flow rate of 100 nL/min. Furthermore, repeatability of the column modification procedure using photografting methods was acceptable, with retention times between replicate columns matching within 9%. [source] Structural formation of hybrid siloxane-based polymer monolith in confined spacesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10-11 2004Kazuyoshi Kanamori Abstract Structural deformation of phase-separated methylsiloxane gel under the influence of a surface has been studied. Competitive wetting of siloxane gel phase on a surface during phase formation is found to significantly affect the final morphology in a confined space. When the spinodal wavelength is sufficiently shorter than the size of the available space, a uniform bicontinuous structure forms in confined geometry. However, gel skeletons in the vicinity of a surface are elongated with decreasing size of the space, and finally when the size of the space becomes shorter than the spinodal wavelength, all the gel phase wets on a surface, showing a "wetting transition". Homogeneous bicontinuous methylsiloxane gels were successfully prepared, avoiding such structural deformation, in a long cylindrical fused silica capillary and used for capillary HPLC. The capillary gels exhibited excellent separation efficiency of nitrobenzenes and it was found that the surface character can be altered by incorporating surfactants, which will enable more advanced and extended control of surface character, depending on the analytes. [source] Porous polymer monolith for surface-enhanced laser desorption/ionization time-of-flight mass spectrometry of small moleculesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2004Dominic S. Peterson Porous poly(butyl methacrylate- co -ethylene dimethacrylate), poly(benzyl methacrylate- co -ethylene dimethacrylate), and poly(styrene- co -divinylbenzene) monoliths have been prepared on the top of standard sample plates used for matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry and the modified plates were used for laser desorption/ionization mass spectrometry (LDI-MS). The hydrophobic porous surface of these monoliths enables the transfer of sufficient energy to the analyte to induce desorption and ionization prior to TOFMS analysis. Both UV and thermally initiated polymerization using a mask or circular openings in a thin gasket have been used to define spot locations matching those of the MALDI plates. The desorption/ionization ability of the monolithic materials depends on the applied laser power, the solvent used for sample preparation, and the pore size of the monoliths. The monolithic matrices are very stable and can be used even after long storage times in a typical laboratory environment without observing any deterioration of their properties. The performance of the monolithic material is demonstrated with the mass analysis of several small molecules including drugs, explosives, and acid labile compounds. The macroporous spots also enable the archiving of samples. Copyright © 2004 John Wiley & Sons, Ltd. [source] Parameters governing reproducibility of flow properties of porous monoliths photopatterned within microfluidic channelsELECTROPHORESIS, Issue 14 2010Mei He Abstract We report the patternability as well as the reproducibility and stability of flow resistance of polymer monolithic beds photopatterned within microfluidic channels as a function of initial reagent composition and preparation conditions. 2-Hydroxyethyl methacrylate and ethylene dimethacrylate-based polymer monoliths were selectively photopatterned within microchannels and their flow resistance was evaluated using a photobleaching, TOF linear flow rate measurement method developed in our lab. This measurement technique was found to be significantly more informative for columns formed in microfluidic channels compared with bulk monolith characterization by mercury intrusion porosimetry. 1-Octanol was determined to provide sharp bed edge formation and relatively low flow resistance by photopatterning relative to other porogenic solvents. Compared with literature formulations which did not achieve good flow stability and reproducibility from batch to batch, using 2-hydroxyethyl methacrylate, ethylene dimethacrylate and 1-octanol as porogenic solvents, less than 4% RSD was achieved in flow stability over 7 days for monoliths prepared with 60,80% crosslinker(monomer+crosslinker) ratio. Column-to-column variation of 5% RSD was obtained in this composition range. These results demonstrate that photopatterning of uniform polymer monolithic beds, which is critical for applications in multiplexed microfluidic systems, requires careful attention to the parameters that affect reproducibility, specifically the porogenic solvent choice and the crosslinker to monomer ratio. [source] Confinement effects on the morphology of photopatterned porous polymer monoliths for capillary and microchip electrophoresis of proteinsELECTROPHORESIS, Issue 14 2008Mei He Abstract We find that the morphology of porous polymer monoliths photopatterned within capillaries and microchannels is substantially influenced by the dimensions of confinement. Porous polymer monoliths were prepared by UV-initiated free-radical polymerization using either the hydrophilic or hydrophobic monomers 2-hydroxyethyl methacrylate or butyl methacrylate, cross-linker ethylene dimethacrylate and different porogenic solvents to produce bulk pore diameters between 3.2 and 0.4,µm. The extent of deformation from the bulk porous structure under confinement strongly depends on the ratio of characteristic length of the confined space to the monolith pore size. The effects are similar in cylindrical capillaries and D-shaped microfluidic channels. Bulk-like porosity is observed for a confinement dimension to pore size ratio >10, and significant deviation is observed for a ratio <5. At the extreme limit of deformation a smooth polymer layer ,300 nm thick is formed on the surface of the capillary or microchannel. Surface tension or wetting also plays a role, with greater wetting enhancing deformation of the bulk structure. The films created by extreme deformation provide a rapid and effective strategy to create robust wall coatings, with the ability to photograft various surface chemistries onto the coating. This approach is demonstrated through cationic films used for electroosmotic flow control and neutral hydrophilic coatings for electrophoresis of proteins. [source] Preparation and HPLC applications of rigid macroporous organic polymer monolithsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10-11 2004Frantisek Svec Abstract Rigid porous polymer monoliths are a new class of materials that emerged in the early 1990s. These monolithic materials are typically prepared using a simple molding process carried out within the confines of a closed mold. For example, polymerization of a mixture comprising monomers, free-radical initiator, and porogenic solvent affords macroporous materials with large through-pores that enable applications in a rapid flow-through mode. The versatility of the preparation technique is demonstrated by its use with hydrophobic, hydrophilic, ionizable, and zwitterionic monomers. Several system variables can be used to control the porous properties of the monolith over a broad range and to mediate the hydrodynamic properties of the monolithic devices. A variety of methods such as direct copolymerization of functional monomers, chemical modification of reactive groups, and grafting of pore surface with selected polymer chains is available for the control of surface chemistry. Since all the mobile phase must flow through the monolith, the convection considerably accelerates mass transport within the molded material, and the monolithic devices perform well, even at very high flow rates. The applications of polymeric monolithic materials are demonstrated mostly on the separations in the HPLC mode, although CEC, gas chromatography, enzyme immobilization, molecular recognition, advanced detection systems, and microfluidic devices are also mentioned. [source] Effect of Surface Modification on the Synthesis of Pore-Filling Polymeric Monoliths in Microfiltration Membranes Made from Poly(propylene) and Poly(ethylene terephthalate)MACROMOLECULAR MATERIALS & ENGINEERING, Issue 3 2007Abdus Salam Abstract The effect of pre-modification on the interaction of macroporous substrates (membranes) with mainly micro- and mesoporous polymer monoliths has been studied. Bulk, porous polymer monoliths were synthesized to optimize the synthesis conditions and their pore morphology, and the data were used as benchmark for this study. Pre-modification of the entire pore surface of PP microfiltration membranes and PET track-etched membranes by UV-initiated grafting with PEGMA was performed using well-established methods, including coating with the photo-initiator, benzophenone. Subsequently, these membranes were functionalized by filling the pores with porous polymer monoliths from MAA and EDMA and compared with membranes that had been functionalized without the pre-modification step. The materials were characterized mainly by the degree of grafting, SEM and by the gas-adsorption-isotherm method. The DG values, after composite-membrane preparation under identical conditions, were not influenced by the pre-modification. However, it could be clearly seen from the SEM images that the pre-modification step prevents the formation of voids at the monolith-membrane pore interface. Larger specific surface area and pore volume values for composite membranes, prepared after pre-modification, fully support the SEM results. Especially large differences in pore structure between the two different composite membranes were found in the mesopore range. The results of this study indicate that it is possible to prepare porous, composite membranes where the trans-membrane transport is exclusively controlled by the pore and surface structure of a functional polymeric monolith, for example, made from a molecularly-imprinted polymer. [source] | ||||||||||