Suspension polymerization of poly(ethylene glycol) methacrylate: a route for swellable spherical gel beads with controlled hydrophilicity and functionality

 Spherical and swellable gel beads were obtained by the suspension polymerization of poly(ethylene glycol) methacrylate macromonomer (PEG-MA). The average size and size distribution properties, the equilibrium swelling behaviour and the protein adsorption characteristics of PEG-MA-based gel beads were determined. In the suspension polymerization system, the organic phase including monomer, cross-linker and diluent solution was dispersed in an aqueous medium by using poly(vinylpyrrolidone) as the stabilizer. The diluent solution was prepared by mixing cyclohexanol and octanol at different volume ratios. The suspension polymerization experiments were designed in two separate parts. In the first part, ethylene glycol dimethacrylate was selected as the cross-linker and swellable PEG-MA-based gel beads were obtained by changing the cross-linker concentration, the monomer/diluent ratio and the stirring rate. In the second part, a more hydrophobic structure, divinylbenzene (DVB) was tried as a cross-linker. In this part, PEG-MA-DVB copolymer beads were obtained by changing the DVB/PEG-MA feed ratio. Then, the hydrophicility of the resulting gel beads could be controlled by changing the feed ratio of hydrophilic macromonomer to hydrophobic cross-linker. This property was also used to control the extent of nonspecific protein adsorption onto the surface of the gel beads. The non specific albumin adsorption onto the gel beads decreased with increasing PEG-MA content. No significant nonspecific adsorption at the isoelectric point of albumin was detected onto the gel beads produced with the higher PEG-MA/DVB feed ratios. For specific albumin adsorption, a triazinyl dye (i.e., cibacron blue, CB F3G-A) was covalently attached onto the surface of the copolymer beads via terminal hydroxyl groups of PEG-MA. The results of albumin adsorption experiments with the CB F3G-A carrying beads indicated that an appreciable specific albumin adsorption capacity could be obtained with the gel beads produced with a PEG-MA/DVB feed ratio of 1.5/4.0. Received: 16 August 1999/Revised: 27 December 1999     

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 property of layer-by-layer alginate hydrogel beads based on multi-phase emulsion technique

Layer-by-layer (LbL) alginate beads, which were prepared by multi-phase emulsion technique, had been fabricated via the ionic crosslinking between calcium ion (Ca²⁺) and the carboxylic group of alginate. The prepared beads were spherical, smooth-surfaced and non-aggregated. The SEM analysis displayed the LbL structure of the beads clearly. It had been demonstrated that the size of the beads was controllable and had a correlation with concentration of sodium alginate (SA) and CaCl₂, ratio of water phase and oil phase (W/O), stirring speed, pH value of the water phase, viscosity of SA as well as the temperature for solidification. Stability studies showed that the beads degraded slowly in simulated gastric fluid and simulated intestinal fluid but degraded sharply when they were moved to simulated colonic fluid. Cytotoxicity study by MTT assay indicated that the prepared beads are slightly toxic. It is hoped that this kind of novel beads could be used in pharmaceutical area and cell culture area.     

种子溶胀悬浮聚合法制备分子印迹聚合物微球

 以酪氨酸为印迹分子 ,甲基丙烯酸为功能单体 ,三羟甲基丙烷三甲基丙烯酸酯 (TRIM )为交联剂 ,采用种子溶胀悬浮聚合法在水溶液中制备了一系列分子印迹聚合物微球 (MIPMs)。利用扫描电镜 (SEM)对此微球的粒径大小、粒径分布、表面孔与孔径分布等进行了分析研究 ,探讨了影响其形貌的主要因素 ,并将所得微球用作固定相研究了其分子选择吸附性能。研究表明 ,种子溶胀悬浮聚合法能够制得单分散性较好的、表面带有微孔的分子印迹聚合物微球 ,且该微球呈现出较好的特异吸附性能。     

Physicochemical characterization of chemical hydrogels based on PVA

In this paper, we report on the physicochemical characterization of hydrogels recently obtained by crosslinking poly (vinylalcohol), PVA, with telechelic PVA (telPVA, bearing terminal aldehydic groups) via acetalization in aqueous solution. These gels were studied by equilibrium swelling, compression modulus measurements, and proton relaxometry experiments. Swelling and compression modulus data allow to estimate the average molecular weight of PVA chain between crosslinks, the average mesh size of the networks, and the polymer–solvent interaction parameter χ₁. The average mesh size of PVA‐telPVA compares well with domain dimensions of diffusionally confined water as detected by NMR relaxometry. Proton relaxometry also showed different network domains in which water is compartmentalized, indicating a complex heterogeneity. The study of the temperature behavior of the nuclear spin–spin relaxation times of the confined water was also considered. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1225–1233, 1999     

Synthesis of macroporous poly(glycidyl methacrylate) microspheres by surfactant reverse micelles swelling method

Macroporous poly(glycidyl methacrylate-ethylene dimethacrylate) [P(GMA-EDMA)] particles with pore size around 140-200 nm and poly(glycidyl methacrylate-divinylbenzene) [P(GMA-DVB)] particles with pore size of 450 nm were prepared by the surfactant reverse micelles swelling method. This method was similar with the conventional suspension polymerization, and the difference was that higher concentration of surfactant was added in the oil phase. When the oil phase containing surfactant was dispersed in aqueous phase, the surfactant reverse micelles in the oil droplets absorbed water from continuous phase. After polymerization, the large pores were formed by the absorbed water. The effects of the amount and type of surfactants, the cooperation of surfactant and diluents, and the crosslinking agent on the morphology of microspheres were investigated. This study provided a new and simple method to prepare microspheres with the pores of several hundred nanometers, which overcame the disadvantages found in the conventional preparation methods of macroporous microspheres.     

Synthesis and modification of supports with an alkylamine and their use in albumin adsorption

The morphological effect of polymeric networks (R) modified with terminal amino groups was studied on the adsorption of bovine serum albumin (BSA). Networks of ethylene glycol dimethacrylate and 2‐hydroxyethyl methacrylate [poly (EGDMA‐co‐HEMA)] were synthesized by suspension polymerization, using different EGDMA contents and agitation speeds. These matrices were characterized by FTIR, mercury intrusion porosimetry, SEM, and swelling degree. The increase of the EGDMA concentration led to the formation of networks with the highest crosslinking degree and porosity. An earlier phase separation yielded a higher aggregation of rigid microspheres, also forming stable pore systems. The increase in coalescence frequency, together with the impeller speed, and the decrease of the stabilizer molecules led to an increment in drop size. Large fused aggregates of microspheres were formed with additional loss of small pores as the stirring was increased, attaining also a higher pore volume (V_p) and a slight decrease of the surface area. Once characterized, networks were activated with butanediolglycidyl ether (BDGE), and then reacted with hexamethylenediamine (HMDA) through coupling reaction. Only the R‐BDGE‐HMDA networks synthesized with the highest EGDMA content and agitation speed showed BSA adsorption. Their base matrices exhibited a V_p higher than 1.4 mL/g, which allows easier protein diffusion into the support. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2557–2566, 2008     

Influence of the surface chemistry on the structural and mechanical properties of silica‐polymer composites

Poly(vinyl alcohol) (PVA) composite films filled with nanometric, monodisperse, and spherical silica particles were prepared by the mixing of an aqueous PVA solution and SiO₂ colloidal suspension and the evaporation of the solvent. Adjusting the solution pH to 5 and 9 controlled the PVA‐SiO₂ interaction. Adsorption isotherms showed a higher PVA/surface affinity at a lower pH. This interaction influenced the composite structure and the particle distribution within the polymer matrix, which was investigated by small‐angle neutron scattering, electron microscopy, and swelling measurements. Most of the mechanical properties could be related to the composite structure, that is, the distribution of clusters within the polymer matrix. The progressive creation of a cluster network within the polymeric matrix as the silica volume fraction increased reduced the extensibility or swelling capacity of the composite. The effect was more acute at a higher pH, at which the surface interaction with PVA was weaker and promoted the interconnection between clusters. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3127–3138, 2003     

Optimal design and characterization of superparamagnetic iron oxide nanoparticles coated with polyvinyl alcohol for targeted delivery and imaging

Superparamagnetic iron oxide nanoparticles (SPION) with narrow size distribution and stabilized by polyvinyl alcohol (PVA) were synthesized. The particles were prepared by a coprecipitation technique using ferric and ferrous salts with a molar Fe3+/Fe2+ ratio of 2. Using a design of experiments (DOE) approach, the effect of different synthesis parameters (stirring rate and base molarity) on the structure, morphology, saturation magnetization, purity, size, and size distribution of the synthesized magnetite nanoparticles was studied by various analysis techniques including X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC) measurements, vibrating-sample magnetometer (VSM), transmission electron microscopy (TEM), UV-visible, and Fourier transform infrared (FT-IR) spectrometer. PVA not only stabilized the colloid but also played a role in preventing further growth of SPION followed by the formation of large agglomerates by chemisorption on the surface of particles. A rich behavior in particle size, particle formation, and super paramagnetic properties is observed as a function of molarity and stirring conditions. The particle size and the magnetic properties as well as particle shape and aggregation (individual nanoparticles, magnetic beads, and magnetite colloidal nanocrystal clusters (CNCs) are found to be influenced by changes in the stirring rate and the base molarity. The formation of magnetic beads results in a decrease in the saturation magnetization, while CNCs lead to an increase in saturation magnetization. On the basis of the DOE methodology and the resulting 3-D response surfaces for particle size and magnetic properties, it is shown that optimum regions for stirring rate and molarity can be obtained to achieve coated SPION with desirable size, purity, magnetization, and shape.     

Polymer-supported reagents. II. Kinetics of esterification of acrylic acid with n-butanol using polymer supported titanium tetrachloride as catalyst

Crosslinked poly(4-vinylpyridine-co-styrene) was prepared and functionalized with titanium tetrachloride to afford the corresponding poly(4-vinylpyridine-co-styrene)-titanium tetrachloride complex. This insoluble functionalized polymer-supported catalyst shows good catalytic activity for esterification reactions. In this article, the kinetics of esterification of acrylic acid with n-butanol is reported. The rate of formation of product depends on many experimental parameters, viz., stirring speed, concentration of acrylic acid, catalyst amount, temperature, percent active site, percent crosslinking, and mesh size of the polymer catalyst. The reaction rates were found to increase with increase in the stirring speed, concentration of acrylic acid, catalyst amount, and temperature, and decreases with increasing percentage crosslinking and mesh size of the polymer beads. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 727–733, 1997     

Highly magnetic latexes from submicrometer oil in water ferrofluid emulsions

The synthesis of functionalized submicrometer magnetic latex particles is described as obtained from a preformed magnetic emulsion composed of organic ferrofluid droplets dispersed in water. Composite (polystyrene/γ‐Fe₂O₃) particles were prepared according to a two‐step procedure including the swelling of ferrofluid droplets with styrene and a crosslinking agent (divinyl benzene) followed by seeded emulsion polymerization with either an oil‐soluble [2,2′‐azobis(2‐isobutyronitrile)] or water‐soluble (potassium persulfate) initiator. Depending on the polymerization conditions, various particle morphologies were obtained, ranging from asymmetric structures, for which the polymer phase was separated from the inorganic magnetic phase, to regular core–shell morphologies showing a homogeneous encapsulation of the magnetic pigment by a crosslinked polymeric shell. The magnetic latexes were extensively characterized to determine their colloidal and magnetic properties. The desired core–shell structure was efficiently achieved with a given styrene/divinyl benzene ratio, potassium persulfate as the initiator, and an amphiphilic functional copolymer as the ferrofluid droplet stabilizer. Under these conditions, ferrofluid droplets were successfully turned into superparamagnetic polystyrene latex particles, about 200 nm in size, containing a large amount of iron oxide (60 wt %) and bearing carboxylic surface charges. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2642–2656, 2006     

Laser speckle analysis on correlation between gelation and phase separation in aqueous methyl cellulose solutions

Structure formation by coupling between formation of crosslinking points and liquid–liquid phase separation was investigated for aqueous methyl cellulose solution by small‐angle X‐ray scattering (SAXS) and light scattering (LS) techniques. The sol–gel phase diagram and the SAXS results suggested that the liquid–liquid phase separation occurred before gelation. By LS measurements, the structure due to the liquid–liquid phase separation was directly observed. By applying speckle analysis on the LS profiles, it was suggested that the gelation and the phase separation strongly coupled each other: the increase in the apparent molecular weight by crosslinking induced the liquid–liquid phase separation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 168–174, 2010     

磁性多孔γ-Fe_2O_3/P(St-DVB-MAA)聚合物微球的制备及其表征

以油酸包裹的γ-Fe2O3为磁性来源,选用苯乙烯(St)、二乙烯苯(DVB)和甲基丙烯酸(MAA)为共聚单体,通过改进的悬浮聚合法,制备了表面含有羧基的多孔磁性高分子微球.利用红外光谱(FTIR)、扫描电子显微镜(SEM)、光学显微镜以及热重分析仪(TG)等对聚合物进行了性能表征.FTIR和光学显微镜结果分析表明,苯乙烯、二乙烯苯和甲基丙烯酸在磁性粒子的表面发生了聚合反应,生成了聚合物包埋磁粉的磁性聚合物复合微球,且微球表面含有羧基;SEM和光学显微镜分析测试结果显示合成的磁性γ-Fe2O3/P(St-DVB-MAA)复合粒子呈球形,微球具有多孔结构,且微球之间不发生团聚,微球粒子粒径分布均匀,大多数粒子粒径分布在0.4~0.9mm之间;TG测试的结果表明,磁性γ-Fe2O3被包覆在聚合物微球之中,且磁性粒子在微球中的包覆率达到12.12%.     

Cucurbit[7]uril moving on side chains of polypseudorotaxanes: Synthesis,characterization, and properties

Novel side chain polypseudorotaxanes with cucurbit[7]uril (CB[7]) threaded onto the side chains are synthesized from a water‐soluble polymer and CB[7] in water by simple stirring at room temperature. CB[7] beads could move from the hexyl groups to the benzyl and a part of viologen units in the side chains of polymer when the molar ratio of CB[7] to the monomer reaches from 1 to 2 as shown by ¹H NMR studies, and it is considered that the hydrophobic and charge‐dipole interactions of CB[7] are the driving forces. The sizes of the polypseudorotaxanes with different molar ratio of CB[7] to 4VBVHeP in aqueous solution increase with increasing the molar ratio of CB[7] to 4VBVHeP as found by DLS and resonance light scattering, while the typical cyclic voltammograms and UV–vis data indicate that CB[7] are not threaded in the viologen units of P4VBVHeP, and the oxidation reduction characteristic of the polymer is remarkably affected by the addition of CB[7]. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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.     

PREPARATION AND THE CULTURE OF LO2 CELLS ON PVA—BASED MICROCARRIERS

Using polyvinyl alcohol(PVA) as raw material and vacuum pump oil as oil phase medium,PVA-based microcarriers were prepared by suspension method,The diameters of the beads were 100-180um,LO2 cells were cultured on PVA-based microcarriers and cytodexⅢ microcarriers.Morphology,attachment and growth rate of LO2 cells were studied.     

Pervaporation separation of water-acetic acid mixtures through poly(vinyl alcohol) membranes crosslinked with glutaraldehyde

Poly(vinyl alcohol) (PVA) membranes crosslinked with glutaraldehyde (GA) were prepared by a solution method for the pervaporation separation of acetic acid-water mixtures. In the solution method, dry PVA films were crosslinked by immersion for 2 days at 40°C in reaction solutions which contained different contents of GA, acetone and a catalyst, HCl. In order to fabricate the crosslinked PVA membranes which were stable in aqueous solutions, acetone was used as reaction medium in stead of aqueous inorganic salt solutions which have been commonly used in reaction solution for PVA crosslinking reaction. The crosslinking reaction between the hydroxyl group of PVA and the aldehyde group of GA was characterized by IR spectroscopy. Swelling measurements were carried out in both water and acetic acid to investigate the swelling behavior of the membranes. The swelling behaviour of a membrane fabricated at different GA content in a reaction solution was dependent on crosslinking density and chemical functional groups created as a result of the reaction between PVA and GA, such as the acetal group, ether linkage and unreacted pendent aldehydes in PVA. The pervaporation separation of acetic acid-water mixtures was performed over a range of 70–90 wt% acetic acid in the feed at temperatures varying from 35 to 50°C to examine the separation performances of the PVA membranes. Permeation behaviour through the membranes was analyzed by using pervaporation activation energies which had been calculated from the Arrhenius plots of permeation rates.     

聚苯胺水基胶体分散液及其复合物的研究 Ⅰ制备、表征及复合物的表观形貌、力学性能

以聚乙烯醇（ＰＶＡ）为稳定剂（ｓｔｅｒｉｃｓｔａｂｉｌｉｚｅｒ）利用分散聚合（ｄｉｓｐｅｒｓｉｏｎｐｏｌｙｍｅｒｉ ｚａｔｉｏｎ）的原理，成功地制备出了稳定的聚苯胺（ＰＡｎ）水基胶体分散液．聚苯胺颗粒的大小受聚合条件如稳定剂浓度、单体浓度、温度以及搅伴状态等的影响．ＰＶＡ通过物理作用吸附在ＰＡｎ颗粒的表面，起到阻止ＰＡｎ颗粒进一步团聚的作用．但这种作用力较弱．ＰＡｎ颗粒的原始尺寸大小约为２０ｎｍ．由此原始颗粒组成了尺寸在１００ｍｍ～２００ｍｍ左右的稳定颗粒     

新型磁性葡聚糖亲和吸附剂的制备及在尿激酶纯化中的应用

 采用反相悬浮包埋技术合成多分散的粒径在 5 0目～ 30 0目的磁性葡聚糖微球 (MDMS)。MDMS经环氧氯丙烷活化后 ,分别键合氨基乙酸、6 氨基己酸和乙二胺作为间隔臂 ,以碳二亚胺为偶联剂 ,分别偶联L 精氨酸甲酯、对氨基苯甲脒和胍基己酸配体 ,制备了 5种磁性亲和吸附剂。研究了分散介质及其粘度和密度、有机相和水相的体积比、表面活性剂的用量、搅拌速度等因素对微球制备的影响。将所制备的磁性亲和吸附剂应用于尿激酶粗品的纯化 ,并讨论了偶联试剂和配体对尿激酶纯化效果的影响。     

RAPID SEPARATION OF FINE PARTICLES FROM DILUTE SUSPENSIONS

A potential rapid solid/liquid separation process of fine particles from dilute aqueous suspensions is introduced (tumbling method). This process involves the separation of one or two types of fine particles in aqueous suspension by heterocoagulation phenomena and is conducted by tumbling suspensions with a macroscopic collector such as glass beads which leads to the settling of particles with the collector. Particularly, it was found that silica (Si0₂: 0.12 μm) particles could effectively be collected by glass beads (80 μ.m) through a bridging effect of hematite (α-Fe₂0₃ : 0.10 μm ) particles. The results were explained in terms of the DLVO theory and the efficient movement of the glass beads collector

A chromatographic separation between silica and hematite particles is also proposed.