Cross-linked Copolymer Beads Research Articles

Fabrication of a novel nitrogen-containing porous carbon adsorbent for protein-bound uremic toxins removal

Protein-bound uremic toxins (PBUTs), the presence of which in the blood is an important risk factor for the progression of chronic kidney disease (CKD), have not been cleared efficiently via traditional hemodialysis methods until now. In this study, biosafe and efficient nitrogen-containing porous carbon adsorbent (NPCA) beads for the clearance of PBUTs were prepared from porous acrylonitrile/divinylbenzene cross-linked copolymer beads followed by pyrolysis. The resulting NPCA beads were characterized via SEM, XPS and nitrogen adsorption/desorption tests. The results demonstrated that the NPCA beads possessed a mesoporous/microporous hierarchical structure with rich nitrogen functional groups on their surfaces and realized efficient PBUTs adsorption in human plasma. More importantly, the efficacy of PBUTs removal was substantially higher than those of commercial adsorbents that are commonly used in clinical uremia treatments. The NPCA beads also exhibited satisfactory removal efficacy towards middle-molecular-weight uremic toxins. The PBUTs removal mechanism of the NPCA beads is ascribed to effective competition between nitrogen-containing NPCA and proteins for PBUT binding. According to hemocompatibility assays, the NPCA beads possessed satisfactory in vitro hemocompatibility. This nitrogen-containing porous carbon adsorbent is an attractive and promising material for blood purification applications in the treatment of clinical uremia.

Preparation of crosslinked quaternary amide–sulfonamide resin for removal of mercury ions from aqueous solutions

Cross-linked copolymer beads were prepared by suspension polymerization of styrene (0.90 mol) and divinyl benzene (DVB) (0.10 mol) mixtures. The resulting copolymer beads with sulfonamide-based quaternary amide functions were prepared in three steps: (1) by chlorosulfonation with chlorosulfonic acid; (2) by sulfonamidation reaction with N,N-dimethylethylenediamine; and (3) by quaternization reaction with chloroacetamide. The resulting polymer resin, which had a chloroacetamide content of 2.50 mmol/g, was effective in extracting mercury from aqueous solutions. The mercury sorption capacity was around 3.0 mmol/g in non-buffered conditions. Experiments performed in identical conditions with several metal ions revealed that Cd(II), Mg(II), Zn(II), and Fe(III) ions also were extractable in low quantities (0.2–0.8 mmol/g). The sorbed mercury could be eluted by repeated treatment with hot acetic acid without hydrolysis of the amide groups.

Synthesis, porous structure, and underwater acoustic properties of macroporous cross-linked copolymer beads

The macroporous and elastomeric beads from polyurethane acrylate (PUA), ethyl methacrylate (EMA), and styrene (St) are prepared by suspension polymerization using n-heptane as porogen and 1,2-divinylbenzene (DVB) as cross-linking agent. The scanning electronic microscope results show that the beads of PUA–EMA–St cross-linked copolymers have many large pores on their surfaces and interiors, and the macroporous sizes are dependent of the copolymer composition and the dosages of cross-linking agents and porogen. Average porous diameters decrease as the dosages of DVB increase and the contents of PUA and porogen decrease. The cross-linked copolymers have two kinds of beads (one with many larger holes on the surface and another with much smaller pores or without pore), when the ratio of PUA to EMA and St is from 6/4 to 4/6. The macroporous and elastomeric beads can improve the underwater acoustic absorption properties of the polyurethane/epoxy (PU/EP) blend elastomer, and the underwater acoustic properties of the composites based on PU/EP blend elastomer and the beads depend mainly on the amounts of the beads and the dosages of porogen.

Adsorptive features of poly(glycidyl methacrylate-co-hydroxyethyl methacrylate): effect of porogen formulation on heavy metal ion adsorption

Preparation of crosslinked copolymer beads based on glycidyl methacrylate (GMA), 2-hydroxyethyl methacrylate (HEMA), and divinyl benzene for the use of heavy metal adsorption has been investigated. In our study, a series of porous copolymer beads were synthesized by suspension polymerization in the presence of porogens, 1-dodecanol, toluene, and heptane at different dilutions. The effect of the porogens on the surface appearance and the porous structure of copolymer beads was studied by scanning electron microscopy and BET method. Diethylene triamine chelating copolymers were obtained through a reaction between amine groups of diethylene triamine and epoxide pendant groups of GMA. Adsorption isotherm and quantitative analysis for adsorption capacity involving copper, chromium, manganese, cadmium, iron, and zinc ions were investigated using atomic absorption spectrophotometer. The adsorption was a function of types of metal ions, adsorption time, and solution properties including pH and metal concentration. Adsorption equilibrium was achieved in approximately 50 min with a maximum adsorption capacity at pH 5.0. The Langmuir isotherm was found to be well fitted on the adsorption behavior. The maximum metal adsorption capacities in single ion solution in mole basis were in the order Cu(II) > Cr(VI) > Mn(II) > Zn(II) > Cd (II) > Fe(II). It was found that introducing porogen in the polymerization mixture produced the copolymer beads with better adsorption capacity. The maximum Cu(II) adsorption capacity of chelating poly(GMA-co-HEMA) beads were 1.35 mmol/g (85.79 mg/g) measured from the beads prepared in the presence of 1-heptane with 50% dilution. Consecutive adsorption–desorption experiments showed that crosslinked poly(GMA-co-HEMA) micro-beads can be reused almost without any change in the adsorption capacity.

Spacer-modified crosslinked copolymer beads for the solid phase synthesis of an amide

The goal of this research was to synthesize an amide using the reaction of a polymer-supported active ester with a primary amine. A new type of the polymer support for an active ester was prepared from poly( ω-bromobutylstyrene-co-divinylbenzene) beads ( 1). Bromine atoms in 1 were replaced by mercapto groups upon treatment with thiourea and subsequent alkaline hydrolysis. Following this, N-hydroxymaleimide was reacted with the polymer ( 3). This reaction introduced N-hydroxysuccinimide moieties into the polymer beads via Michael addition, yielding a resin ( 4). Resin 4 was reacted with a model carboxylic acid in the presence of a water-soluble esterification reagent (WSC). This yielded resin ( 5), which contained polymer-bound active ester groups. Reaction of 5 with a primary amine gave the objective amide. Resulting amides had a higher purity than those prepared by solid phase synthesis using the corresponding polymer support, which was derived with poly(chloromethylstyrene-co-divinylbenzene) beads and a traditional liquid phase synthesis. Resin 5, after use in the amide synthesis, was regenerated into the active ester form for the repeated use.

Preparation and characterization of azlactone functionalized polymer supports and their application as scavengers

A series of cross-linked porous copolymer supports based on N-( p-vinylbenzoyl)-2-methylalanine (VBM), styrene and divinylbenzene was prepared by aqueous suspension copolymerization in the presence of butan-2-ol used as porogen. The cross-linked copolymer beads were characterized by elemental analysis, scanning electron microscopy (SEM), FT-IR and confocal Raman spectrometries. It was observed that the VBM incorporation was effective and homogeneous within the beads. Those VBM functionalized supports were converted into azlactone functionalized supports using acetic anhydride and their scavenging efficiency towards different amines was measured. It appeared that 90% of benzylamine was quenched after 5 h.

Production of porous suspension polymers using a continuous tubular reactor

The conventional method for the synthesis of porous cross-linked copolymer beads is by suspension polymerisation. Suspension polymerisation reactions are generally performed in a stirred tank, which generally results in a large size distribution. By careful control of the polymerisation conditions, polymer beads can be produced using a tubular poly(tetrafluoroethylene) continuous reactor. Such beads are produced with the same average pore size, but with a lower degree of polydispersity than analogous systems produced in a batch reactor (stirred tank). This is achieved by density-matching the droplet and continuous phases (by the use of a brominated monomer or a porogenic diluent) and increasing the viscosity of the monomer phase (with the addition of small amounts of polystyrene).

Swellable ethylene glycol dimethacrylate-hydroxyethylmethacrylate copolymer beads

In this study, Swellable poly(EGDMA/HEMA) beads in the size range of 30–170 μm with different size distributions were produced by suspension copolymerization of ethylene glycol dimethacrylate (EGDMA) and hydroxyethylmethacrylate (HEMA) in aqueous media. Poly(vinyl alcohol) and benzoyl peroxide were used as the stabilizer and the initiator. The diluent, i.e. toluene was included in the recipe of the second group of copolymerizations. The beads were characterized by optical microscopy, FTIR and FTIR-DRS. Crosslinked, transparent, nonporous and Swellable (up to a swelling ratio of 31.2%) poly(EGDMA/HEMA) beads were obtained in which there was no toluene in the recipe. While copolymerizations with toluene provided Swellable (up to a swelling ratio of 57.1%), opaque, porous and crosslinked copolymer beads. In the polymerization (without toluene) HEMA is mainly incorporated on the outer layers (near surface) of the beads. In this case, increase in the EGDMA/HEMA ratio resulted larger beads with wider size distributions, and with lower swellabilities. The porosity of the dry copolymer beads were studied with mercury pycnometric method. Incorporation of toluene within the recipe (in the modified polymerization) caused pronounced effects both on bead size and swellability. Larger beads with broader size distributions, with higher swellabilities were obtained when the relative amount of toluene increased.

Perfluorocarbon Fluids: Universal Suspension Polymerization Media

The use of perfluorocarbon (PFC) fluids such as perfluorinated alkanes as universal suspension polymerization media is described. PFC fluids are inert, stable, and immiscible with most organic compounds and with water. In utilization of these unusual immiscibility and stability properties, cross-linked copolymer beads bearing reactive functional groups were prepared by direct suspension copolymerization of the reactive monomer with a difunctional cross-linker in PFC fluids. Examples of functional groups include isocyanate, hydroxyl, acid chloride, carboxylic acid, aziridine, and trimethoxysilane. The suspension homopolymerization of methacrylic acid and cationic suspension polymerizations of vinyl ethers in PFC fluids were also achieved. The role of dispersants in these nonaqueous media was studied through the suspension copolymerization of styrene and divinylbenzene. The advantages of using PFC fluids in suspension polymerization over water were summarized.

Iron(III) chelating resins IV. Crosslinked copolymer beads of 1-(β-acrylamidoethyl)-3-hydroxy-2-methyl-4(1H)-pyridinone (AHMP) with 2-hydroxyethyl methacrylate (HEMA)

Iron(III) chelating beads have been synthesized by copolymerization of 1-(β-acrylamidoethyl)-3-hydroxy-2-methyl-4(IH)-pyridinone (AHMP) with 2-hydroxyethyl methacrylate (HEMA), and ethyleneglycol dimethacrylate (EGDMA) as the crosslinking agent. The synthesis of the AHMP-HEMA beads was performed by suspension polymerization of AHMP, HEMA and EGDMA in benzyl alchol—20% aqueous NaCl solution using 2,2′-azobisisobutyronitrile (AIBN) as the initiator and polyvinylalcohol (40–88) as a suspending agent. The crosslinked copolymer beads were characterized by IR, and the AHMP content was determined by elemental analysis. The AHMP-HEMA beads were not too hydrophilic, and the copolymers absorbed at equilibrium only 40–50% water. It was found that the copolymer beads were very stable at 25°, but some degradation was observed at 121°. The AHMP-HEMA copolymers were able to chelate iron(III) and the chelation was dependent on the conditions such as pH and temperature. However, the capacities towards iron(III) chelation were always found to be much lower than the calculated values. The influence of the polymeric matrix on the iron(III) chelating ability was studied with iron(III) chelating resins containing various polymeric matrices. It was found that the iron(III) chelating efficiencies of the resins were strongly affected by their hydrophilicities. The low chelating efficiency of the AHMP-HEMA beads (0–40%) is probably due to their poor swelling in water.

Kinetic Behavior of Lightly Crosslinked Chelating Resins Containing Amidoxime Groups for Batchwise Adsorption of UO2 2+

Abstract Lightly crosslinked poly(acrylonitrile-co-divinylbenzene) beads (RN-5) have been synthesized by suspension polymerization. The use of dichloroethane and chloroform as a porogen produced lightly crosslinked copolymer beads having highly porous structures. The chelating resins containing amidoxime groups (RNH-5) have been prepared by the reaction of copolymer beads with NH2OH in MeOH. The resulting chelating resins have been used in the batchwise adsorption of UO2 2+ from nitrate solutions containing 0.01 mol·dm−3 UO2 2+ at pH 3.25. In order to get some measure of the relative performance of each resin in kinetic terms, the extraction of UO2 2+ was monitored with time and some adsorption profiles were obtained. An increase in porogen content resulted in a marked increase in the batchwise adsorption of UO2 2+. Alkaline treatment allowed a high swelling and hence rapid accessibility of UO2 2+ to the ligands. Even after 30 minutes, the alkali-treated resins were 50% loaded.

Swelling behavior of pH-sensitive copolymers based on styrene and 4-(or 2-)vinylpyridine

Two series of lightly cross-linked copolymer beads based on styrene (St) and 4-(or 2-)rinylpyridine (4VP or 2VP) were synthesized, and their equilibrium swelling behavior in aqueous solution was studied as a function of pH and ionic strength. A wide range of pH-sensitive swelling behavior could be obtained using a range of compositional changes of copolymers. Over a fairly narrow pH range, the polymer swells as the medium becomes more acidic, consistent with protonation of the VP units. With an increase in the ratio of St to 4VP, the pH at which the swelling transition occurs shifts to lower values and the extent of swells as the decreases

Chelating Resins Containing 1,4,8,11-Tetraazacyclotetradecane-5,7-dione Based on Crosslinked Copolymer Beads of the Macroreticular Type

Chelating resins containing a macrocyclic ligand, 1, 4, 8, 11-tetraazacyclotetradecane-5, 7-dione, were prepared by ligand reactions with two different crosslinked copolymer beads of the macroreticular type: chloromethylated styrene- divinylbenzene (RCS) and glycidyl methacrylate-divinylbenzene (RG) copolymers. Although both resins have nearly equal amounts of the fixed ligand, the RG-based resin (RGD) shows a much higher uptake of Cu(II) than does the RCS- based resin (RCSD). This indicates that the complexing ability of the fixed ligand is strongly influenced by copolymer matrices. A further detailed study of RGD revealed that the characteristics of RGD include high selectivity toward Cu(II) and a rapid elution rate of Cu(II) with an aqueous solution of strong acid. The usefulness of RGD in the separation of Cu(II) has been demonstrated by means of column operation.