Anion-exchange supermacroporous monolithic matrices with grafted polymer brushes of N,N-dimethylaminoethyl-methacrylate

Graft polymerization using potassium diperiodatocuprate as initiator was found to be an effective and convenient method for grafting functional polymer of N,N-dimethylaminoethyl methacrylate (DMAEMA) onto superporous polyacrylamide gels, so-called cryogels (pAAm cryogels). It was possible to achieve grafting degrees up to 110% (w/w). The two-step graft polymerization i.e. first activation of the matrix followed by displacement of initiator solution with the monomer solution, decreased pronouncedly the soluble homopolymer formation. The efficiency of graft polymerization using a two-step technique increased up to 50% (w/w) at a monomer conversion of 10%, compared to 10% graft efficiency with 60-70% monomer conversion for one-step direct graft polymerization. The pAAm cryogels grafted in one-step and two-step procedures, respectively, behaved similarly when binding low-molecular weight ligand but showed very different behavior for sorption of a high-molecular-weight ligand, bovine serum albumin (BSA). The differences in behavior were rationalized assuming different structure of the graft polymer layers and tentacle-type BSA binding to the grafted polymer.     

Graft polymerization of vinyl monomers inside macroporous polyacrylamide gel,cryogel, in aqueous and aqueous‐organic media initiated by diperiodatocuprate(III) complexes

Graft polymerization initiated by diperiodatocuprate(III) complex (Cu(III)) initiator was found to be an effective and convenient method for graft polymerization of vinyl monomers onto macroporous polyacrylamide gels, the so‐called cryogels (pAAm‐cryogels). The effect of time, temperature, monomer and initiator concentration during the graft polymerization in aqueous and aqueous‐organic media was studied. The graft polymerization of water‐soluble monomers as [2‐(methacryloyloxy)ethyl]‐trimethylammonium chloride, 2‐hydroxyethyl methacrylate, N‐isopropylacrylamide, and N,N‐dimethylacrylamide proceeds with higher grafting yield in aqueous medium, as compared with that in aqueous‐organic media. Graft polymerization in aqueous‐organic media such as water–DMSO solutions allows grafting of water‐insoluble monomers such as glycidyl methacrylate and N‐tert‐butylacrylamide with high grafting degrees of 100 and 410%, respectively. It was found that the deposition of initiator on the pore surface of cryogels promoted graft polymerization by facilitating the formation of the redox couple Cu(III)‐acrylamide group. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1952–1963, 2006     

An improved capillary model for describing the microstructure characteristics, fluid hydrodynamics and breakthrough performance of proteins in cryogel beds

A capillary-based model modified for characterization of monolithic cryogels is presented with key parameters like the pore size distribution, the tortuosity and the skeleton thickness employed for describing the porous structure characteristics of a cryogel matrix. Laminar flow, liquid dispersion and mass transfer in each capillary are considered and the model is solved numerically by the finite difference method. As examples, two poly(hydroxyethyl methacrylate) (pHEMA) based cryogel beds have been prepared by radical cryo-copolymerization of monomers and used to test the model. The axial dispersion behaviors, the pressure drop vs. flow rate performance as well as the non-adsorption breakthrough curves of different proteins, i.e., lysozyme, bovine serum albumin (BSA) and concanavalin A (Con A), at various flow velocities in the cryogel beds are measured experimentally. The lumped parameters in the model are determined by matching the model prediction with the experimental data. The results showed that for a given cryogel column, by using the model based on the physical properties of the cryogel (i.e., diameter, length, porosity, and permeability) together with the protein breakthrough curves one can obtain a reasonable estimate and detailed characterization of the porous structure properties of cryogel matrix, particularly regarding the number of capillaries, the capillary tortuousness, the pore size distribution and the skeleton thickness. The model is also effective with regards to predicting the flow performance and the non-adsorption breakthrough profiles of proteins at different flow velocities. It is thus expected to be applicable for characterizing the properties of cryogels and predicting the chromatographic performance under a given set of operating conditions.     

Preparation of supermacroporous cryogels with improved mechanical strength for efficient purification of lysozyme from chicken egg white

A novel, facile, and robust strategy was proposed to increase the pore size and mechanical strength of cryogels. By mixing the monomers of acrylamide and 2‐hydroxyethyl methacrylate as the precursor, a monolithic copolymer cryogel with large interconnected pores and thick pore walls was prepared. Hydrogen bonding between the two monomers contributed to the entanglement and aggregation of the copolymers, thickening the pore walls and resulting in larger pore sizes. Analysis via mercury porosimetry demonstrated that the interconnected pore diameter of the copolymer cryogel ranged from 10‐350 µm, which was far larger than that of the cryogels from one monomer (10‐50 µm). Additionally, the thicker pore walls of the copolymer cryogel improved its mechanical strength. Affinity cryogels were prepared through covalent immobilization using Tris(hydroxymethyl)aminomethane as a coupling agent, and the affinity binding of lysozymes on Tris‐cryogel was evaluated by the Langmuir isothermal adsorption with the maximum adsorption capacity of 360 mg/g. Compared with that of the Tris‐cryogels produced from one monomer, the copolymer Tris‐cryogel exhibited higher adsorption capacity and lysozyme purity, when the chicken egg white solution flowed solely driven by gravity. This work provides a new avenue for designing and developing supermacroporous cryogels for bioseparation.     

Immobilization of Inulinase on Concanavalin A-Attached Super Macroporous Cryogel for Production of High-Fructose Syrup

In this study, concanavalin A (Con A)-attached poly(ethylene glycol dimethacrylate) [poly(EGDMA)] cryogels were used for immobilization of Aspergillus niger inulinase. For this purposes, the monolithic cryogel column was prepared by radical cryocopolymerization of EGDMA as a monomer and N,N′-methylene bisacrylamide as a crosslinker. Then, Con A was attached by covalent binding onto amino-activated poly(EGDMA) cryogel via glutaraldehyde activation. Characterization of cryogels was performed by FTIR, EDX, and SEM studies. Poly(EGDMA) cryogels were highly porous and pore size was found to be approximately 50–100 μm. Con A-attached poly(EGDMA) cryogels was used in the adsorption of inulinase from aqueous solutions. Adsorption of inulinase on the Con A-attached poly(EGDMA) cryogel was performed in continuous system and the effects of pH, inulinase concentration, and flow rate on adsorption were investigated. The maximum amount of inulinase adsorption was calculated to be 27.85 mg/g cryogel at 1.0 mg/mL inulinase concentration and in acetate buffer at pH 4.0. Immobilized inulinase was effectively used in continuous preparation of high-fructose syrup. Inulin was converted to fructose in a continuous system and released fructose concentration was found to be 0.23 mg/mL at the end of 5 min of hydrolysis. High-fructose content of the syrup was demonstrated by thin layer chromatography.     

Hydrophobic cryogels for DNA adsorption: Effect of embedding of monosize microbeads into cryogel network on their adsorptive performances

As alternative hydrophobic adsorbent for DNA adsorption, supermacroporous cryogel disks were synthesized via free radical polymerization. In this study, we have prepared two kinds of cryogel disks: (i) poly(2‐hydroxyethyl methacrylate‐N‐methacryloyl‐l ‐tryptophan) [p(HEMA‐MATrp)] cryogel containing specific hydrophobic ligand MATrp; and (ii) monosize p(HEMA‐MATrp) particles synthesized via suspension polymerization embedded into p(HEMA) cryogel structure to obtain p(HEMA‐MATrp)/p(HEMA) composite cryogel disks. These cryogel disks containing hydrophobic functional group were characterized via swelling studies, Fourier transform infrared spectroscopy, elemental analysis, surface area measurements and scanning electron microscopy. DNA adsorption onto both p(HEMA‐MATrp) cryogel and p(HEMA‐MATrp)/p(HEMA) composite cryogels was investigated. Maximum adsorption of DNA on p(HEMA‐MATrp) cryogel was found to be 15 mg/g polymer. Otherwise, p(HEMA‐MATrp)/p(HEMA) composite cryogels significantly increased the DNA adsorption capacity to 38 mg/g polymer. Composite cryogels could be used repeatedly without significant loss on adsorption capacity after 10 repetitive adsorption–desorption cycles. Copyright © 2013 John Wiley & Sons, Ltd.     

Characterization of a novel continuous supermacroporous monolithic cryogel embedded with nanoparticles for protein chromatography

A novel continuous supermacroporous monolithic cryogel embedded with nanometer-size particles was prepared by the radical cryogenic co-polymerization of acrylamide (AAm), N,N'-methylene-bis-acrylamide (MBAAm), allyl glycidyl ether (AGE) and the dispersed surfactant-stabilized Fe3O4 nanoparticles under the freezing-temperature variation condition in a glass column. This special separation matrix has interconnected supermacropores with pore size of 10-50 microm, which permit the free-passage of microbial cells or cell debris in the culture fluids and then is interest in downstream processes. The axial liquid dispersion coefficients of the new continuous supermacroporous monolithic bed at different liquid flow rates were obtained by measuring residence time distributions (RTDs) using tracer pulse-response method. The experimental results showed that the axial liquid dispersion within the bed was weak in a wide water flow rate of 0.5-15 cm/min. The axial dispersion coefficient was found to be increased exponentially with the increase of liquid flow rate. Chromatographic process of bovine serum albumin (BSA) in the cryogel monolithic bed was carried out to reveal the protein breakthrough and elution characteristics. Compared with other reported cryogel beds in literature, the protein adsorption capacity of the present cryogel bed was improved due to the embedded nano-sized solid adsorbents in the gel matrix. Microstructure morphology of the embedded nanoparticles in the cryogel and the gel matrix structure were also analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) in this paper.     

阴离子型接枝微粒PDAC/PSA的制备及对谷氨酸的吸附性能初探

采用自由基聚合法在溶液聚合体系中将功能单体丙烯酰氧乙基三甲基氯化铵(DAC)接枝于聚苯乙烯伯胺微球(PSA)表面,制备了接枝微粒PDAC/PSA,考察了主要因素对接枝聚合的影响,并初步探究了其对L-谷氨酸的吸附特性。结果表明,在反应温度25℃、单体质量分数为6%、引发剂占单体质量的1.2%的条件下,可制得接枝度为431mg/g的接枝微粒,其对L-谷氨酸的吸附量达140mg/g。     

Ce(IV) ion initiated graft polymerization of glycidylmethacrylate onto a demineralized bone matrix: effect of reaction parameters

Studies on chemical modification of demineralized bone matrix (DBM) have opened new arenas in the field of clinical orthopedics owing to its potential osteoinductivity with desired chemical functionality. To widen its usage to biomolecular delivery, graft polymerization of glycidylmethacrylate onto DBM was carried out by a free-radical initiating process using ceric ammonium nitrate as an initiator. The evidence of the grafting reaction was examined by chemical analysis using Fourier transform IR spectroscopy. The grafting condition was standardized by regulating the reaction parameters such as the concentrations of the backbone, the monomer and the initiator, the polymerization temperature and time. The optimum polymerization temperature and time to have the maximum grafting yield were 40 °C and 3 h, respectively. The percentage of grafting and the percentage of grafting efficiency were determined as a function of the reaction parameters, and both were found to increasing initially and thereafter decrease in most of the cases. The grafting results are discussed in a detailed fashion and a reaction mechanism is proposed.     

Ring-opening metathesis polymerization for the preparation of norbornene-based weak cation-exchange monolithic capillary columns

Functionalized monolithic columns were prepared via ring-opening metathesis polymerization (ROMP) within silanized fused silica capillaries with an internal diameter of 200 μm by in situ grafting. This procedure is conducted in two steps, the first of which is the formation of the basic monolithic structure by polymerization of norborn-2-ene (NBE) and 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo,endo-dimethanonaphthalene (DMN-H6) in a porogenic system (toluene and 2-propanol) using RuCl₂(PCy₃)₂(CHPh) as ROMP initiator. In the second step the still active initiator sites located on the surface of the structure-forming microglobules were used as receptor groups for the attachment (“grafting”) of functional groups onto the monolithic backbone by flushing the monolith with 7-oxanorborn-2-ene-5,6-carboxylic anhydride (ONDCA). Functionalization conditions were first defined that did not damage the backbone of low polymer content (20%) monoliths allowing high-throughput chromatographic separations. Variation of the functionalization conditions was then shown to provide a means of controlling the degree of functionalization and resulting ion-exchange capacity. The maximum level of in situ ONDCA grafting was obtained by a 3 h polymerization in toluene at 40 °C. The weak cation-exchange monoliths obtained provided good separation of a standard peptide mixture comprising four synthetic peptides designed specifically for the evaluation of cation-exchange columns. An equivalent separation was also achieved using the lowest capacity column studied, indicative of a high degree of robustness of the functionalization procedure. As well as demonstrably bearing ionic functional groups enabling analyte separation in the cation-exchange mode, the columns exhibited additional hydrophobic characteristics which influenced the separation process. The functionalized monoliths thus represent useful tools for mixed-mode separations.     

Grafting of amino functional monomer onto initiator-modified polystyrene particles

Polystyrene nanoparticles with grafted chains of an amino functionalized polymer were prepared by a two-step polymerization process. In the first step, the polystyrene seed particles were synthesized by the conventional batch emulsion polymerization using terpolymer HAS (hydroperoxide monomer, acrylic acid, and styrene) as a surface-active initiator. The surface of the obtained particles contains carboxyl groups, which are responsible for the latex stability, and residual undecomposed hydroperoxide groups. Therefore, in the second step, an amino functional monomer was grafted onto the hydroperoxide modified polystyrene particles by a "grafting from" approach. X-ray photoelectron spectroscopy, NMR, and scanning electron microscopy were used to examine the surface of the amino functionalized particles. The amount of incorporated amino groups onto the particles was determined by fluorescenometric titration. In general, the number of amino groups on the particle surface increased with the increase of the functional monomer content in the reaction mixture. The incorporation of the functional monomer was also confirmed by electrophoretic measurements. Final particles possess amphoteric character due to the presence of amino and carboxyl groups on the surface. Adsorption of human immunoglobulins G onto the amino functionalized particles was studied as a function of pH and ionic strength. The covalent binding of human IgG was performed using the glutaraldehyde preactivation method. The immunoreactivity of the latex-IgG complex was examined by the latex agglutination test.     

Grafting of methyl methacrylate onto natural rubber in supercritical carbon dioxide

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber (NR) was carried out by supercritical carbon dioxide (scCO₂) swelling polymerization with benzoyl peroxide (BPO) as an initiator. Fourier transform–infrared spectroscopy (FT–IR) was used to confirm the formation of graft copolymers with the characteristic bands of symmetric C?O and C? O? C stretching vibrations at 1728 cm^?1 and 1147 cm^?1, respectively. The effects of the rubber‐to‐monomer ratio, amount of initiator, reaction time, and pressure on the monomer grafting level (GL) and grafting efficiency (GE) were investigated, and the optimum conditions for the preparation of NR‐g‐MMA were found to be 70:30 of the rubber‐to‐monomer ratio, 1.2% of the initiator content, and the reaction pressure of 23 MPa for 6 h. The thermal behavior of the NR and the different NR/MMA molar ratio grafted copolymer samples was studied by differential scanning calorimetry (DSC). The observed glass transition temperature (T_g) was consistent with the GL. The tensile strength, modulus of elasticity, elongation at break, hardness, and oil resistance of graft copolymers were determined and compared with the values of NR and that of polymerization products prepared in traditional toluene solution. The results showed that the tensile strength, modulus of elasticity, hardness and oil resistance were greatly improved after modification in scCO₂. Copyright © 2007 John Wiley & Sons, Ltd.     

Graft Copolymerization of Methyl Acrylate in Starch Using Ceric Ion/Thiourea Initiator System

Abstract

Graft copolymers of methyl acrylate onto starch were prepared in aqueous solution at 29°C using ceric ion and the batch and modified batch polymerization (with incremental addition of monomer and initiator) processes. It was found that the conversion of monomer to polymer, the graft levels, the efficiency and frequency of grafting were markedly higher for the modified batch process. The effect of thiourea on the grafting characteristics of ceric ion initiated copolymerization of methyl acrylate was also examined. The results show that at comparable ceric ion concentrations, the molecular weight and the frequency of grafting methyl acrylate were higher in the presence of thiourea.     

Visible light‐induced living surface grafting polymerization for the potential biological applications

A novel visible light‐induced living surface grafting polymerization was developed by a strategy in which isopropyl thioxanthone (ITX) was first photoreduced under UV light and sequentially coupled onto the surface of polymeric substrates, and the produced isopropyl thioxanthone‐semipinacol (ITXSP) “dormant” groups were subsequently reactivated under visible light to initiate a surface grafting polymerization. By using glycidyl methacrylate (GMA) and low‐density polyethylene (LDPE) films as models, a “living” surface grafting polymerization initiated by ITXSP under visible light at room temperature was observed. Both the surface grafting chain length versus grafting conversion of monomer and the grafting polymerization rate versus monomer concentration demonstrated a linear dependence, which is in accord with the known characteristics of living polymerization. The livingness rendered it possible to accurately control the thickness of the grafted layer by simply altering the irradiation time. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Phys, 2009     

氯丁胶乳乳液接枝甲基丙烯酸甲酯的反应动力学

采用乳液聚合法将甲基丙烯酸甲酯(MMA)接枝到氯丁胶乳上,红外光谱和核磁共振氢谱证实了接枝产物的生成。 研究了反应温度、乳化剂浓度、引发剂浓度和单体浓度对表观聚合速率的影响。 结果表明,当反应温度为50 ℃,引发剂叔丁基过氧化氢 四乙烯五胺（t-BHP/TEPA）用量为氯丁胶乳干重的0.5%,单体/聚合物质量比m(M)∶m(P)=3∶5,乳化剂十二烷基连苯醚二磺酸钠（DSB）用量为单体总质量1%时,单体转化率和接枝效率分别为99.1%和54.9%。 聚合反应动力学关系式为：Rp=Kc(E)0.15c(I)0.30c(MMA)1.41,式中,K为常数,在40~55 ℃范围内,聚合反应的表观活化能Ea＝60.2 kJ/mol。 接枝聚合基本符合自由基反应机理。     

Graft polymerization of vinyl monomers onto nanosized alumina particles

To enhance the interfacial interaction in alumina nanoparticles filled polymer composites, an effective surface modification method was developed by grafting polystyrene and polyacrylamide onto the particles. That is, the alumina surface was firstly treated with silane, followed by radical grafting polymerization in aqueous or non-aqueous systems. Results of infrared spectroscopy and dispersiveness in solvents demonstrated that the desired polymer chains have been covalently bonded to the surface of the alumina particles. They also greatly changed their surface characteristics. In addition, effects of polymerization conditions, including ways of monomer feeding, concentrations of monomer and initiator, and reaction time, on the grafting reaction were presented. It was found that the growing polymer radicals and/or the grafted polymer chains had a blocking effect on the diffusion of radicals or monomers towards the surface of nanoalumina. This was due to the fact that the interaction between the solvent and the grafted polymers was weaker than that between the grafted polymers and the nanoparticles.     

Preparation of cation-exchange membrane containing bi-functional groups by radiation induced grafting of acrylic acid and sodium styrene sulfonate onto HDPE: Influence of the synthesis conditions

Electron beam radiation induced grafting of acrylic acid (AA) and sodium styrene sulfonate (SSS) onto high-density polyethylene (HDPE) membranes was investigated by the pre-irradiation method, and a cation-exchange membrane containing bifunctional groups was synthesized. The effects of grafting conditions such as monomer concentration, radiation dose and temperature on grafting yield were studied. The dependence of grafting yield on pre-irradiation dose and monomer concentration was found to be 0.54 and 2.21, respectively. The activation energy for the grafting was calculated to be 22.2 kJ/mol. Infrared spectroscopy analysis of the grafted membrane confirmed the existence of sulfonate and carboxylic acid groups.     

硅烷气相接枝水解交联聚丙烯

硅烷气相接枝水解交联聚丙烯;聚丙烯;气相接枝;硅烷交联     

Molecularly imprinted supermacroporous cryogels for cytochrome c recognition

Molecular imprinting is an attractive biomimetic approach that creates specific recognition sites for the shape and functional group arrangement to template molecules. The purpose of this study is to prepare cytochrome c-imprinted poly(hydroxyethyl methacrylate) (PHEMA)-based supermacroporous cryogel which can be used for the separation of cytochrome c from protein mixtures. N-Methacryloyl-(L)-histidinemethylester (MAH) was used as the metal-coordinating monomer. In the first step, Cu(2+) was complexed with MAH, and the cytochrome c imprinted PHEMA (MIP) cryogel was prepared by free radical cryopolymerization initiated by N,N,N',N'-tetramethylene diamine at -12°C. After polymerization is completed, the template cytochrome c molecules were removed from the MIP cryogel using 0.5 M NaCl solution. The maximum cytochrome c binding amount was 126 mg/g polymer. Selective binding studies were performed in the presence of lysozyme and bovine serum albumin. The relative selectivity coefficients of MIP cryogel for cytochrome c/lysozyme and cytochrome c/bovine serum albumin were 1.7 and 5.2 times greater than those of the non-imprinted PHEMA cryogel, respectively. The selectivity of MIP cryogel for cytochrome c was also confirmed with fast protein liquid chromatography. The MIP cryogel could be used many times with no remarkable decrease in cytochrome c binding capacity.     

Poly(hydroxyethyl methacrylate)‐based composite cryogel with embedded macroporous cellulose beads for the separation of human serum immunoglobulin and albumin

A novel super‐macroporous monolithic composite cryogel was prepared by embedding macroporous cellulose beads into poly(hydroxyethyl methacrylate) cryogel. The cellulose beads were fabricated by using a microchannel liquid‐flow focusing and cryopolymerization method, while the composite cryogel was prepared by cryogenic radical polymerization of the hydroxyethyl methacrylate monomer with poly(ethylene glycol) diacrylate as cross‐linker together with the cellulose beads. After graft polymerization with (vinylbenzyl)trimethylammonium chloride, the composite cryogel was applied to separate immunoglobulin‐G and albumin from human serum. Immunoglobulin‐G with a mean purity of 83.2% and albumin with a purity of 98% were obtained, indicating the composite cryogel as a promising chromatographic medium in bioseparation for the isolation of important bioactive proteins like immunoglobulins and albumins.