Double emulsion droplets as microreactors for synthesis of magnetic macroporous polymer beads

An easy method is presented to fabricate monodisperse magnetic macroporous polymer beads（MMPBs）. Waterin-oil high internal phase emulsion（HIPE） is prepared by emulsifying aqueous iron ions solution in an oil phase containing monomers. The HIPE is introduced into a simple microfluidic device to fabricate monodisperse（water-in-oil）-in-water double emulsion droplets. The droplets serve as microreactors to synthesize Fe3O4 nanoparticles and are on-line polymerized to form MMPBs. The prepared MMPBs display uniform size, interconnected porous structure, superparamagnetic behavior and uniform distribution of Fe3O4 in polymer matrix. The MMPBs are characterized by scanning electron microscopy（SEM）, Fourier transform infrared spectroscopy（FTIR）, X-ray diffraction（XRD）, transmission electron microscopy（TEM）, vibrating sample magnetometry（VSM）. We believe that this method is a universal technique in preparing macroporous nanocomposite beads.     

Monodisperse polymer beads as packing material for high-performance liquid chromotography: Effect of divinylbenzene content on the porous and chromatographic properties of poly(styrene-co-divinylbenzene) beads prepared in presence of linear polystyrene as a porogen

The effect of concentration of divinylbenzene on pore size distribution and surface areas of micropores, mesopores, and macropores in uniformly sized porous poly(styrene-co-divinylbenzene) beads prepared in the presence of linear polystyrene as a component of the porogenic mixture has been studied. While the total specific surface area was clearly determined by the content of divinylbenzene, the sum of pore volumes for mesopores and macropores as well as their size distribution does not change within a broad range of DVB concentrations. Consequently, the size exclusion chromatography calibration curves are almost identical for all the beads prepared with different percentages of crosslinking monomer. However, the more crosslinked beads have better mechanical and hydrodynamic properties. © 1994 John Wiley & Sons, Inc.     

Improvement of extraction capability of magnetic molecularly imprinted polymer beads in aqueous media via dual-phase solvent system

In this study, a novel and simple dual-phase solvent system for the improvement of extraction capability of magnetic molecularly imprinted polymer (MIP) beads in aqueous sample was proposed. The method integrated MIP extraction and micro-liquid-liquid extraction (micro-LLE) into only one step. A magnetic MIP beads using atrazine as template was synthesized, and was applied to aqueous media by adding micro-volume of n-hexane to form a co-extraction system. The magnetic MIP beads preferred to suspend in the organic phase, which shielded them from the disturbance of water molecule. The target analytes in the water sample was extracted into the organic phase by micro-LLE and then further bound to the solid-phase of magnetic MIP beads. The beads specificity was significantly improved with the imprinting efficiency of template increasing from 0.5 to 4.4, as compared with that in pure aqueous media. The extraction capacity, equilibration process and cross-selectivity of the MIP dual-phase solvent extraction system were investigated.The proposed method coupled with high-performance liquid chromatography was applied to the analysis of atrazine, simazine, propazine, simetryn, prometryne, ametryn and terbutryn in complicated sample such as tomato, strawberry juice and milk. The method is selective, sensitive and low organic solvent-consuming, and has potential to broaden the range of MIP application in biological and environmental sample.     

Magnetic polymer beads: Recent trends and developments in synthetic design and applications

The paper describes the synthesis, properties and applications of magnetic polymer beads. State-of-the-art, future challenges, and promising trends in this field are analyzed. New applications in oil recovery are described.     

A polymeric chiral surface functionality immobilized on uniformly sized macroporous polymer beads

Uniformly sized functionalized macroporous polymer beads were prepared by either a classical copolymerization method or recently reported in situ surface modification method utilizing chiral methacrylamide as a functional modifier. To evaluate conformational and/or specific differences in their surface chiral functionality, we applied chromatographic evaluation techniques. The prepared modified beads were utilized as chiral stationary phase in high-performance liquid chromatography (HPLC). Those prepared by the in situ surface modification method tended to show higher chiral recognition ability than those by the classical copolymerization method, even if the equivalent amount of the chiral functional group was involved within polymer beads. Detailed chromatographic studies exhibited the in situ surface modification method could lead to polymeric methacrylamide functionality on the surface within relatively large pore size regions of the macroporous polymer beads, while the classical copolymerization method tended to form less polymeric surface functionality. The difference in the chiral surface functionality on both of macroporous polymer beads afforded drastic change in chromatographic chiral recognition ability. Complete resolution of a drug, thalidomide could be achieved on the chiral stationary phase with the polymeric chiral surface functionality, while no resolution was found on that with the monomeric one even if the same chiral methacrylamide was used as a modifier to prepare the chiral stationary phases. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2747–2757, 1997     

Cyclodextrin dimer derivatives used as stationary phase for capillary gas chromatography

Summary Four cyclodetrin dimer derivatives were synthesized by linking two single cyclodextrin derivatives with difunctional spacer at the primary side of cyclodetrin. The separation properties of these cylodextrin dimer derivatives as CGC stationary phases were investigated and compared with those of the unbridged native cyclodextrin derivative. The results show that two recognition sites and one link spacer of these cyclodextrin dimer derivatives cooperate in separation and affect the separation of disubstituted benzene positional isomers.     

Water-soluble ionic liquids as novel stabilizers in suspension polymerization reactions: engineering polymer beads

Aqueous solutions of ionic liquids have been used as novel and environmentally friendly reaction media to synthesize and "control" the size of different cross-linked polymer beads by suspension polymerization reactions. It was found that the investigated ionic liquids can act as novel stabilizing agents of the suspensions as a result of their surface-active properties. The results have demonstrated that the average size of polymer beads can be varied from the macro- to the nanoscale and their surface area can also be "adjusted" by this synthetic approach. Furthermore, the use of a combination of ionic liquids and water for the synthesis of polymers, the simple isolation of the products formed in this polymerization procedure, as well as the recycling of the continuous medium for further reactions open up possibilities for the development of "new and green" polymerization processes.     

Porous glass beads as stationary phase in supercritical fluid chromatography

Summary Porous glass beads were evaluated as the stationary phase in supercritical fluid chromatography using methanol or diethyl ether as the mobile phase. Separation of oligomers of styrene and methylphenylsiloxane were demonstrated by using a microcolumn packed with prous glass beads.     

Pore size in one‐step swelling and polymerization of monodisperse polymer beads

Crosslinked polystyrene beads were prepared at low swelling ratios by one‐step swelling and polymerization method. Pore size of the beads was observed based on the GPC calibration curves. It is found that: (1) the pore size increases as the swelling ratio decreases; (2) when a good solvent is used as the porogen the pore size increases with the crosslinking monomer content; and (3) at high crosslinking monomer content the pore size does not depend on the porogen solubility. The effects are discussed in terms of polymer miscibility, including phase separation between the seed and bead polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3270–3277, 2000     

Preparation and characterization of spherical polymer packings from polybutadiene for size-exclusion chromatography

Porous polymer spherical particles for column packings in nonaqueous size-exclusion chromatography (SEC) were prepared from 1,2-syndiotactic polybutadiene by suspension and evaporation method. The polymer microbeads obtained were crosslinked by radical reaction between 2-vinyl groups in polybutadiene with ultraviolet radiation, to render them insoluble. These microbeads have wider chromatographic separation width than polystyrene column packings. In addition, the polybutadiene microbeads did not show the excessive retention observed with commercial polystyrene columns for polycyclic aromatic compounds. Therefore, a close correlation between the elution volume and M, for polycyclic aromatic compounds was observed with polybutadiene microbeads columns.     

Surface-modified polystyrene beads as photografting imprinted polymer matrix for chromatographic separation of proteins

A new and facile fabricating method for lysozyme molecularly imprinted polymer beads (lysozyme-MIP beads) in aqueous media was presented. Mesoporous chloromethylated polystyrene beads (MCP beads) containing dithiocarbamate iniferter (initiator transfer agent terminator) were used as supports for the grafting of lysozyme imprinted copolymers with acrylamide and N,N′-methylenebisacrylamide through surface initiated living-radical polymerization (SIP). After the polymerization, a layer of lysozyme-MIP was formed on the MCP beads. The SIP allowed an efficient control of the grafting process and suppressed solution propagation. Therefore, the obtained lysozyme-MIP beads had a large quantity of well-distributed pores on the surface without any visible gel formation in solution and were more advantageous comparing with traditional MIPs which were prepared by traditionally initiated radical polymerization. The obtained composites were characterized by Fourier transform infrared spectroscopy, elemental analysis, nitrogen sorption analysis and scanning electron microscopy. Chromatographic behaviors of the column packed with lysozyme-MIP beads exhibited ability in separating lysozyme from competitive protein (bovine hemoglobin, bovine serum albumin, ovalbumin or cytochrome c) in aqueous mobile phase.     

Hierarchical porous polymer beads prepared by polymerization-induced phase separation and emulsion-template in a microfluidic device

Porous polymer beads（PPBs） containing hierarchical bimodal pore structure with gigapores and meso-macropores were prepared by polymerization-induced phase separation（PIPS） and emulsion-template technique in a glass capillary microfluidic device（GCMD）. Fabrication procedure involved the preparation of water-in-oil emulsion by emulsifying aqueous solution into the monomer solution that contains porogen. The emulsion was added into the GCMD to fabricate the（water-in-oil）-in-water double emulsion droplets. The flow rate of the carrier continuous phase strongly influenced the formation mechanism and size of droplets. Formation mechanism transformed from dripping to jetting and size of droplets decreased from 550 μm to 250 μm with the increase in flow rate of the carrier continuous phase. The prepared droplets were initiated for polymerization by on-line UV-irradiation to form PPBs. The meso-macropores in these beads were generated by PIPS because of the presence of porogen and gigapores obtained from the emulsion-template. The pore morphology and pore size distribution of the PPBs were investigated extensively by scanning electron microscopy and mercury intrusion porosimetry（MIP）. New pore morphology was formed at the edge of the beads different from traditional theory because of different osmolarities between the water phase of the emulsion and the carrier continuous phase. The morphology and proportion of bimodal pore structure can be tuned by changing the kind and amount of porogen.     

Monodisperse polymer beads as packing material for high-performance liquid chromatography. Preparation of macroporous poly(2,3-epoxypropyl vinylbenzyl ether-co-divinylbenzene) beads,their properties,and application to HPLC separations

In search for HPLC separation media with new surface chemistries, a styrene-based monomer, 2,3-epoxypropyl vinylbenzyl ether, containing reactive epoxide groups has been syn-thesized and copolymerized with divinylbenzene in a suspension polymerization. The process involves the use of size monodisperse particles that are swollen with monomer and then polymerized in the presence of a porogenic diluent consisting of a mixture of 4-methyl-2-pentanol and octane. The effect of concentration of divinylbenzene on the pore size dis-tribution and the specific surface area of the resulting uniformly sized porous poly(2,3-epoxypropyl vinylbenzyl ether-co-divinylbenzene) beads has been studied. The epoxide groups of the copolymer have been hydrolyzed and the beads used for reversed-phase chro-matography of both small molecules and proteins to show the effect of hydrophobicity of the matrix on the separation properties. Reversed-phase chromatography of alkylbenzenes follows the expected pattern while for proteins the hydrolyzed beads with the highest content of the crosslinking monomer exhibit a remarkable deviation from the predicted retention characteristics. © 1995 John Wiley & Sons, Inc.     

Synthesis of highly monodisperse quantum dot‐loaded polymer beads by impregnation and precipitation techniques

A novel approach to the synthesis of highly monodisperse quantum dot‐loaded polymer beads by combining impregnation and precipitation techniques was reported. The monodisperse poly(glycidyl methacrylate) (PGMA) beads were first synthesized by dispersion polymerization. Then, the PGMA beads were chemically modified to generate carboxyl groups, and impregnation of cadmium ions (Cd²⁺) inside the beads. Subsequently, the cadmium ions were reacted with thioacetamide to form cadmium sulfide (CdS) quantum dots within the polymer beads. The morphology, structure, and properties of CdS quantum dot‐loaded polymer beads were studied by field emission scanning electron microscope (SEM), transmission electron microscope, fluorescence spectrophotometer, fluorescence microscope, Fourier transform infrared spectroscopy, powder X‐ray diffraction, and thermogravimetric analysis. The results indicated that the CdS quantum dot‐loaded polymer beads had an average size of 1.4 μm, and were highly monodisperse. More interestingly, the CdS quantum dots distributed evenly within the polymer beads, which provide very strong fluorescence intensity. The existence of carboxyl groups on the quantum dot‐loaded polymer beads was measured quantitatively, and was found to be 0.2 mmol/g. These CdS quantum dot‐loaded polymer beads involving functional carboxyl groups would have potential applications in biological immunoassay and photoelectronic fields. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Preparations and properties of uniform size macroporous polymer beads prepared by two-step swelling and polymerization method utilizing divinyl succinate or divinyl adipate as a crosslinking agent

Uniform size macroporous polymer beads were prepared through a typical two-step swelling and polymerization method utilizing divinyl succinate or divinyl adipate as well as ethylene dimethacrylate as crosslinking agents. Stable macroporous polymer beads with good size monodispersity and a slightly nonspherical shape were obtained by homopolymerization of divinyl succinate in cyclohexanol as porogen. BET measurements indicated that the beads prepared by homopolymerization of divinyl succinate and copolymerization of divinyl succinate with vinyl p-tert-butylbenzoate, as well as homopolymerization of ethylene dimethacrylate had relatively large specific surface area. In contrast, copolymerization of divinyl succinate with methyl methacrylate afforded beads having a very small specific surface area. Similarly, all the beads prepared using divinyl adipate had very small specific surface area, while size exclusion chromatography in tetrahydrofuran suggested that these beads acquired a porous structure as a result of swelling. When used as packing materials for high-performance liquid chromatography, the beads prepared with divinyl adipate showed unexpected molecular recognition toward flat solutes in reversed phase liquid chromatography in contrast to those prepared with ethylene dimethacrylate. Copolymerizations with methyl methacrylate led to a decrease in molecular recognition, while those with vinyl p-tert-butylbenzoate enhanced the selectivity. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of benzyl β-cyclodextrins used as GC stationary phases

Summary Heptakis(2,6-di-O-benzyl)-β-CD(I), heptakis(2,6-di-O-benzyl-3-O-pentyl)-β-CD(II), heptakis(2,6-di-O-benzyl-3-O-methyl)-β-CD(III) and heptakis(2,6-di-O-benzyl-3-O-acetyl)-β-CD(IV) derivatives were synthesized and identified. Their thermal stabilities were tested using PyGC. These CD derivatives are stable up to 300°C and suitable for use as gas chromatographic stationary phases. The fused silica capillary columns coated with heptakis(2,6-di-O-benzyl-3-O-methyl)-β-CD and heptakis(2,6-di-O-benzyl-3-O-pentyl)-β-CD showed excellent chromatographic properties in separating positional isomers.     

Fine control of the porous structure and chromatographic properties of monodisperse macroporous poly(styrene-co-divinylbenzene) beads prepared using polymer porogens

The porous structure of monodisperse macroporous beads can be controlled by using soluble polymers with well-defined structural characteristics as part of the porogenic mixture. In general, the use of linear polystyrene as a porogen in the preparation of poly (styrene-co-divinylbenzene) beads shifts the pore size distribution towards larger pores. While a direct correlation between pore size and molecular weight of the porogen has been established, the chemical composition of the polymer porogen has no effect on the porous and chromatographic properties of the beads. These findings suggest that the average molar volume of the porogenic system is important while the miscibility of the polymer porogen with the crosslinked polymer that is formed is of little relevance. © 1994 John Wiley & Sons, Inc.