Shaofeng Xie

Design of reactive porous polymer supports for high throughput bioreactors: poly(2-vinyl-4,4-dimethylazlactone-co-acrylamide- co-ethylene dimethacrylate) monoliths.

Enzymatic bioreactors with both high flow characteristics and mechanical stability based on macroporous poly(2-vinyl-4, 4-dimethylazlactone-co-acrylamide-co-ethylene dimethacrylate) monoliths have been prepared. Covalent immobilization of trypsin on these support is achieved in a single reaction step using the azlactone functional groups. Optimization of hydrophilic/hydrophobic properties of the monolith affords a support that does not shrink in water and leads to immobilized enzyme that shows high activity in the hydrolysis of both low and high molecular weight substrates such as L-benzoyl arginine ethyl ester and casein. The catalytic activity of the monolithic reactor is maintained even at a flow velocity of 180 cm/min, which substantially exceeds those reported in the literature for packed bed reactors.

Rapid reversed-phase separation of proteins and peptides using optimized 'moulded' monolithic poly(styrene-co-divinylbenzene) columns

Monolithic macroporous poly(styrene-co-divinylbenzene) stationary phases have been prepared by free radical polymerization within the confines of 4.6-mm I.D. chromatographic columns. The optimized porous properties allow the mobile phase to flow through these columns at flow-rates of up to 10 ml/min. As opposed to the simultaneously tested columns packed with either silica or synthetic polymer beads, the monoliths exhibit only modest back pressure. The monolithic columns were able to separate mixtures of peptides and proteins in a very short time. Under the optimized conditions, the separation of five proteins can be easily achieved in less than 20 s.

Preparation of porous hydrophilic monoliths: Effect of the polymerization conditions on the porous properties of poly (acrylamide‐co‐N,N′‐methylenebisacrylamide) monolithic rods

Molded macroporous monoliths with pores sizes up to 1000 nm have been prepared by copolymerization of the hydrophilic monomers, acrylamide, and N,N′-methylenebisacrylamide, in the presence of a porogenic diluent. A combination of dimethylsulfoxide and 2-heptanol was selected from a broad spectrum of solvents and water soluble polymers to achieve the optimum composition of the porogenic mixture. In addition to the composition of the porogen the porous properties of the monolithic rods can also be optimized through changes in the percentage of both N,N′-methylene-bisacrylamide (crosslinking monomer) and azobisisobutyronitrile (free radical initiator) used for the polymerization. The hydrophilic monoliths may be used in the separation of biological polymers, solid-phase extraction, or for immobilization of proteins.

Porous polymer monoliths: an alternative to classical beads.

Porous polymer monoliths are a new category of materials developed during the last decade. These materials are prepared using a simple molding process carried out within the confines of a closed mold. Polymerization of a mixture that typically contains monomers, free-radical initiator, and porogenic solvent affords macroporous materials with large through-pores that enable flow-through applications. The versatility of the preparation technique is demonstrated by its use with hydrophobic, hydrophilic, ionizable, and zwitterionic monomers. The porous properties of the monolith can be controlled over a broad range. These, in turn, determine the hydrodynamic properties of the devices that contain the molded media. Since all the mobile phase must flow through the monolith, the mass transport within the molded material is dominated very much by convection, and the monolithic devices perform well even at very high flow rates. The applications of monolithic materials are demonstrated on the chromatographic separation of biological compounds and synthetic polymers, electrochromatography, gas chromatography, enzyme immobilization, molecular recognition, and in advanced detection systems. Grafting of the pore walls with selected polymers leads to materials with completely changed surface chemistries.

Effect of porosity and surface chemistry on the characterization of synthetic polymers by HPLC using porous polymer monolithic columns

Monolithic 50 × 4.6 mm ID poly(styrene-co-divinylbenzene), poly(glycidyl methacrylate-co-ethylene dimethacrylate), and poly(2,3-dihydroxypropyl methacrylate-co-ethylene dimethacrylate) columns have been tested in the high-performance liquid chromatography (HPLC) separation of polystyrenes and poly(methyl methacrylate) standards. The separation process involves precipitation of the macromolecules on the macroporous monolithic column followed by progressive redissolution and elution utilizing a gradient of the mobile phase. While very good separations of individual components of mixtures of both polystyrenes and poly(methyl methacrylates) can be readily achieved using poly(styrene-co-divinylbenzene) monolith, methacrylate-based columns do not afford good separations under identical conditions. This unexpected finding appears to be the result of significant differences between the porous properties and chemistries of the two types of monolithic materials.