Chitosan‐comb‐graft‐polyethylene glycol monomethacrylate—Synthesis,characterization, and evaluation as a biomaterial for hemodialysis applications

Chitosan was reacted with “Polyethylene glycol monomethacrylate” (PEGm) using a redox initiation method. Different compositions were prepared by varying the relative amount of PEGm in the feed. A maximum of 88% yield with 320% grafting could be achieved. The graft copolymerization was confirmed by FTIR, thermal, and XRD studies. Higher graft % could be achieved as the monomer used is a macro monomer of PEG and the resultant graft is a comb‐like polymer. Grafting with PEGm did not affect the thermal stability of chitosan film significantly, however, it resulted in a marginal increase in the tensile strength of the films in the dry state. The products showed much improved swelling at pH 7.4 and pH 1.98 compared to the virgin chitosan. The preliminary biocompatibility evaluation showed that the materials are blood compatible and non‐cytotoxic. Though the permeability to low molecular weight solutes like creatinine and glucose was equal to or better than commercial cellulose membranes, the copolymer films expressed comparatively less permeability to these solutes initially, due to the crystalline domains of PEO grafts that impede the transport. On exposure in the medium, this effect is nullified culminating in better permeability. The crystallization of PEG grafts was very helpful in preventing the permeation of the high molecular weight solute albumin, the leakage of which above a certain limit is dangerous to the patient. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Separation of liquid mixtures by using polymer membranes. III. Grafted poly(vinyl alcohol) membranes in vacuum permeation and dialysis

A series of poly(vinyl alcohol) membranes were modifed by radiation-induced graft copolymerization with acrylic acid and methacrylic acid monomers. These grafted poly(vinyl alcohol) membranes were then tested for their separation and permeability characteristics in vacuum permeation and dialysis experiments. The permselectivity of the membranes toward methanol and water was studied on a vacuum permeation apparatus at 30, 40, and 50°C. The permeation process was found to be a temperature-activated process. The logarithm of the permeation rate varied linearly with the reciprocal of the absolute temperature. The permeability of the grafted membranes was found to increase with the degree of grafting, with no appreciable selectivity toward water in binary mixtures. The acrylic acid-grafted membranes generally showed greater improvement in permeability than the methacylic-grafted membranes. The permeability of the grafted membranes toward methanol, sodium chloride, urea, creatinine, and uric acid was studied in a dialyzer. In all cases, the grafted membranes showed an improved permeability toward these solutes over the commercial poly(vinyl alcohol) membranes. The dialysis results were then compared with those obtained for dialysis-grade cellophane membranes. For the case of sodium chloride, urea, and methanol, the permeability of the grafted membranes was comparable to that of cellophane. A comparison of commercial and grafted poly(vinyl alcohol) membranes in their permeability toward ionic solutes exhibited somewhat anomalous behavior in that the permeability of the commercial membranes was higher than that of the grafted membranes. This related to the ionic nature of the modified membrane. The permeability coefficients determined in the dialysis experiments were found to be directly related to the degree of hydration of the grafted membrane. This behavior was attributed to changes in the size and shape of voids within the membrane structure.     

Influence of degree of grafting and grafting temperature on the permeabilities of grafted polypropylene membranes

Polypropylene dialysis membranes were prepared using cobalt-60 gamma radiation to directly graft 2-hydroxyethyl methacrylate (HEMA) onto polypropylene (PP) membranes. The surface structures of both the grafted membranes and the PP membrane were observed by using FTIR–PAS and ESCA methods. The X-ray diffraction diagrams of the PP and PP-g-HEMA membranes indicated a transformation process of the β-form toward the α-form crystallinity with increasing degree of grafting. The SEM data of the membrane grafted under a low grafting temperature showed many spheres of PHEMA embedded in the PP matrix, whose size was well distributed and increased with the degree of grafting. The influences of the degree of grafting and grafting temperature on the permeabilities of PP-g-HEMA membranes toward urea and creatinine were studied in a dialyzer. In all cases, the PP-g-HEMA membrane obtained under higher grafting temperature showed higher permeability toward those solutes. The permeation coefficients of urea and creatinine through the PP-g-HEMA membrane obtained at 59°C were about 10.4 and 28.8 times that through the PP membrane, respectively. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:83–89, 1998     

Chitosan‐grafted poly(hydroxyethyl methacrylate‐co‐glycidyl methacrylate) membranes for reversible enzyme immobilization

Epoxy group‐containing poly(hydroxyethyl methacrylate/glycidyl methacrylate), p(HEMA/GMA), membrane was prepared by UV initiated photopolymerization. The membrane was grafted with chitosan (CH) and some of them were chelated with Fe(III) ions. The CH grafted, p(HEMA/GMA), and Fe(III) ions incorporated p(HEMA/GMA)‐CH‐Fe(III) membranes were used for glucose oxidase (GOD) immobilization via adsorption. The maximum enzyme immobilization capacity of the p(HEMA/GMA)‐CH and p(HEMA/GMA)‐CH‐Fe(III) membranes were 0.89 and 1.36 mg/mL, respectively. The optimal pH value for the immobilized GOD preparations is found to have shifted 0.5 units to more acidic pH 5.0. Optimum temperature for both immobilized preparations was 10°C higher than that of the free enzyme and was significantly broader at higher temperatures. The apparent K_m values were found to be 6.9 and 5.8 mM for the adsorbed GOD on p(HEMA/GMA)‐CH and p(HEMA/GMA)‐CH‐Fe(III) membranes, respectively. In addition, all the membranes surfaces were characterized by contact angle measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3084–3093, 2007     

Permeation and Separation Characteristics of Acetic Acid‐Water Mixtures by Pervaporation through Acrylonitrile and Hydroxy Ethyl Methacrylate Grafted Poly(vinyl alcohol) Membrane

Abstract

In this study, acrylonitrile (AN) and hydroxyl ethyl methacrylate (HEMA) were grafted onto poly(vinyl alcohol) (PVA) using cerium (IV) ammonium nitrate as initiator at 30°C. The graft copolymer was characterized using the Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The grafted PVA membranes (PVA‐g‐AN/HEMA) were prepared by a casting method, and used in the separation of acetic acid‐water mixtures by pervaporation. The effects of the membrane thickness, operating temperature, and feed composition on the permeation rate and separation factor for acetic acid‐water mixtures were studied. Depending on the membrane thickness, the temperature and feed composition PVA‐g‐AN/HEMA membranes gave separation factors 2.26–14.60 and permeation rates of 0.18–2.07 kg/m²h. It was also determined that grafted membranes gave lower permeation rates and greater separation factors than PVA membranes. Diffusion coefficients of acetic acid‐water mixtures were calculated from permeation rate values. The Arrhenius activation parameters were calculated for the 20 wt.% acetic acid content in the feed using the permeation rate and the diffusion data obtained at between 25–50°C.     

Radiation-induced graft copolymerization of 2-hydroxyethyl methacrylate onto chloroprene rubber membrane. II. Characterization of grafting copolymer

The cobalt-60 radiation-induced graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto a chloroprene rubber (CR) membrane has been studied in ethanol. The structure, morphology, crystallinity, thermal stability, and hydrophility of graft copolymer were characterized by means of Fourier transform infrared photoacoustic spectroscopy, scanning electron microscopy, wide-angle X-ray diffraction, differential thermal gravimetric analysis, and contact angle test methods, respectively. The permeabilities of urea, creatinine, and creatine through the CR and CR-g-HEMA membranes are investigated in a dialysis cell, and the permeation mechanism is also discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1745–1750, 1998     

Use of radiation-grafted polyethylene in dialysis of low molecular weight metabolites

Radiation-induced graft copolymerization of styrene/maleic anhydride (Sty/MAn) binary monomers into high-density polyethylene (HDPE) has been studied. The optimum conditions under which a high grafted yield is obtained and the grafting process proceeds homogeneously have been determined. A suitable solvent for the grafting process is acetone for a (Sty/MAn) composition of (70/30 mol%). The permeability of low molecular weight metabolites (urea, creatinine, uric acid, glucose and phosphate salts) through the untreated and treated grafted HDPE membranes has been studied. The hydrophilicity of the membrane, the degree of grafting and the molecular weight and chemical structure of the metabolites have a great influence on the transport properties of the membrane. For all solutes investigated, the permeability increases with the degree of grafting. The basic metabolites show higher permeation rates through the modified membrane compared with that for the acidic metabolite, especially phosphate salts. The permeabilities of vitamin B₁₂, bovine albumin and KCl through the treated grafted membranes have been measured and those of the high molecular weight compounds are low. © 1999 Society of Chemical Industry     

Influence of monosodium glutamate additive on the morphology and permeability characteristics of polyamide dialysis membranes

Membranes were prepared with dope solutions of various concentrations of polyamide and monosodium glutamate (MSG) additive for dialysis applications. The results show that the membranes with higher MSG concentrations had higher water uptakes and porosities. The membranes were characterized with scanning electron microscopy (SEM) and atomic force microscopy techniques and evaluated in terms of the permeability of solutes, such as urea and creatinine. The cross‐sectional structure of the membranes prepared without MSG additive or with a low MSG concentration were dense, and their surfaces consisted of large‐sized nodule aggregates. The permeation of solutes was less through these membranes. When the amount of additive in the membrane solution was sufficient, macrovoids were seen in the SEM images, and the sizes of nodules were small, which caused an increase in the diffusive permeability of solutes. The surfaces of the membranes with higher MSG concentrations were found to be smooth; this could be useful for the dialysis process. The contact angles of these membranes were also lower; this indicated that this additive improved the hydrophilicity of the membranes. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dialysis membranes from polyethylene films grafted with acrylic acid

Low‐density polyethylene‐g‐poly(acrylic acid) membranes were prepared by the direct radiation grafting of aqueous acrylic acid solutions (containing Mohr's salt) onto low‐density polyethylene films and were irradiated at two different irradiation doses (2 and 3 Mrad) at a dose rate of 0.02 Mrad/h. Two series of polyethylene‐g‐poly(acrylic acid) membranes with 100 and 150% grafting were obtained. The free carboxylic acid groups in the grafted films were converted into the corresponding acrylates by reactions with different metal salts. The swelling (water uptake) and dialysis permeability of glucose and urea through the grafted membranes in different metal‐ion forms were investigated. The prepared membranes showed good permeability to both solutes, which increased as the hydrophilicity of the membrane increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 10–14, 2004     

Permeability through cellulose membranes grafted with vinyl monomers in a homogeneous system. VIII. N-vinylpyrrolidone-grafted cellulose membranes

The homogeneous grafting of N-vinylpyrrolidone (NVP) onto cellulose was carried out in a dimethyl sulfoxide/paraformaldehyde (DMSO/PF) solvent system. The diffusive permeabilities of solutes through the NVP-grafted cellulose membranes, apparent activation energy for solute permeation through them, states of water in them, and their microphaseseparated structures were investigated. The solute permeability through the grafted membranes was superior to that through the cellulose membrane cast from the DMSO/PF solution of cellulose. The total water and nonfreezing water contents of the grafted membranes were larger than those of the cellulose membrane. The difference in permeability through the membranes was not correlated quantitatively with the amount of each state of water in them. Activation energies for permeation of solutes through the grafted membranes were similar to those through the cellulose membrane. © 1994 John Wiley & Sons, Inc.     

Synthesis of pH‐responsive polyethylene terephthalate track‐etched membranes by grafting hydroxyethyl‐methacrylate using atom‐transfer radical polymerization method

pH‐responsive polyethylene terephthalate (PET) track‐etched membranes were synthesized by grafting 2‐hydroxyethyl‐methacrylate (HEMA) on the surface of the membrane via atom transfer radical polymerization. The controllability of grafting polymerization of HEMA on membrane surface is systematically investigated. The pH‐responsive characteristics of PET‐g‐poly(2‐hydroxyethyl‐methacrylate) (PHEMA) gating membranes with different grafted PHEMA chain lengths are measured by tracking the permeation of water solution with different pH values. The results show that the grafting polymerization is controllable, and the permeation of grafted membranes is affected by the grafted PHEMA chain lengths on the surface of membrane. The results also demonstrate that the grafted PET membranes exhibit reversible pH‐response permeation to environmental pH values. Desired pH‐responsive membranes are obtained by controlling the grafted PHEMA chain lengths via atom transfer radical polymerization method. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40912.     

Synthesis of highly selective copolymer membranes and their application for the dehydration of tetrahydrofuran by pervaporation

Acrylonitrile was copolymerized with 2‐hydroxyethyl methacrylate (HEMA) at three different copolymer compositions by emulsion polymerization to produce polyacrylonitrile–2‐hydroxyethyl methacrylate (PANHEMA) copolymer membranes containing increasing amounts of HEMA from PANHEMA‐1 to PANHEMA‐3. The dehydration of tetrahydrofuran (THF) over a concentration range of 0–14 wt % water in the feed was studied by pervaporation with these three copolymer membranes. The permeate water flux and separation factor for water was measured over the same concentration range at 30, 40, and 50°C. Among the copolymer membranes, PANHEMA‐1 exhibited a reasonable water flux (34.9 g m^?2 h^?1) with a very high water selectivity (264), whereas PANHEMA‐3 showed a higher water flux (52 g m^?2 h^?1) but a lower water selectivity (176.5) for highly concentrated THF (0.56 wt % water in the feed) at 30°C. The permeation factors of water for all of the membranes were much greater than unity, which signified a strong positive coupling effect of THF on water permeation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 728–737, 2007     

Preparation and permeability of solutes through acrylic acid-g-methylcellulose copolymer membranes

Graft copolymer membranes from the methylcellulose and the acrylic acid were prepared and their properties and the permeability of four solutes were estimated. Acrylic acid-g-methylcellulose (AA-g-MC) copolymer dissolved in aqueous acetone solvent was cast to prepare membranes followed by the subsequent crosslinking either with aluminium potassium sulfate or by the thermal-curing method. The equilibrium water content in the membrane increased with the volume fraction of acetone in the aqueous acetone solvent system. Membrane, the ionically crosslinked with the aluminum potassium sulfate, showed the water content in the range of 38.5 and 58.4% and 0.25–0.33 kg/mm² of the tensile strength in the wet state. Compared with ionically crosslinked membranes, thermally dried membranes exhibited a more dense structure, resulting in lower water contents and higher mechanical strength. Experimental results on the permeation of four small and midsize solutes through the graft copolymer membranes revealed the molecular weight dependence of the permeability coefficient. The higher the degree of swelling, the greater the permeability coefficient. Ionically crosslinked membranes had higher solute permeability than the commercial Cuprophane membrane had. © 1993 John Wiley & Sons, Inc.     

Grafting of acrylamide to nylon-6 by the electron-beam preirradiation technique. II. Kinetic aspects and film permeability

Single- and multilayered laminated nylon-6 films were grafted with acrylamide (AM) using the electron-beam preirradiation technique. Very high grafting yields were obtained within short time periods. Grafting onto single films was shown to proceed via “diffusion free” pseudo zero-order kinetics. Grafting onto multilayered films was diffusion controlled. SEM and EDAX measurements indicate uniform grafting of single-film membranes and asymmetric grafting of membranes prepared by grafting onto multilayered films. The permeability of grafted membranes to a number of permeants was found to increase with extent of grafting. The specific permeability to both water and solutes exceeded that of the dialysis grade cellophone at 500% graft. The selectivity of grafted films towards various solutes had also been found to be higher than that of cellophane.     

Investigation of the thin film crystallization of a DNA copolymer hybrid composed of chitosan

We describe for the first time the crystallization in thin films of a DNA copolymer composed of a low molecular weight chitosan backbone to which a sequence of nucleic acids is grafted (chitosan‐g‐ssDNA). As assessed by atomic force microscopy, optical microscopy and spectroscopy, crystallization occurs due to intermolecular hydrogen bonding in which the nucleic acid strands engage. The morphology of the crystals depends on the affinity for the surface of the polymer segments that compose the DNA copolymer hybrid. The nucleic acids adsorb on mica and silica on which side‐branched structures are observed whereas chitosan interacts preferentially with gold, and dendritic crystals are assembled. Attenuated total reflectance infrared spectroscopy supports the high ordering of the structure and the establishment of strong intermolecular interactions by hydrogen bonding. © 2016 Society of Chemical Industry     

改性聚苯胺膜在CO_2/CH_4分离中的应用研究

合成了一种由N-乙基苯胺和苯胺共聚的高聚物,并制备了其4种掺杂态共聚物膜。实验中在不同压力、不同进料组成下测试了共聚物膜及聚砜膜对CO2/CH4混合气的分离性能。实验结果表明:掺杂态不同对气体的分离性能有很大影响,其中二次掺杂态的分离系数最高,可达70,而去掺杂态的渗透速率最高,CO2可达2.15 GPU[1 GPU=7.501×10-10cm3/(cm2.s.Pa)],CH4达到0.049 GPU,均高于聚砜膜和文献中报道的聚苯胺膜的值,这是由于N-乙基的引入,改变了聚合物链的柔韧性。     

Morphology and Thermal Characteristics of Polyamide/Monosodium Glutamate Membranes

The membranes were prepared with various concentrations of polyamide and monosodium glutamate additive for dialysis application in this work. The membranes were characterized by determining creatinine diffusive permeability and by obtaining scanning electron microscope images and thermal characteristics. The results show that a membrane prepared without additive has a thick skin layer and a nonporous sublayer. The permeation of creatinine solute does not take place due to this dense (thick/nonporous) structure. When an additive is used in membrane synthesis, the thickness of skin layer reduces and voids are present, which results in permeation of this unwanted solute through the membrane.     

Nylon 4/HEMA chemical homografted membrane

To enhance the degree of grafting, homografting copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto nylon 4 using a chemical initiator has been attempted. The factors that affect the grafting copolymerization are the concentration of reactants, reaction time, and temperature. The dialysis permeabilities of solutes, water content, surface energy, mechanical properties, and blood compatibility of the membrane were investigated. Under the same reaction conditions, the degree of grafting by the homografting method is remarkably higher than of the heterografting method for the nylon 4–HEMA grafting system. The dialysis permeabilities of NaCl, vitamin B₁₂, and ovalbumin of the homografted membrane with a 14.8% degree of grafting are 2.760, 0.392, and 0.073 × 10^?5 cm²/min, respectively. These permeabilities are higher than the corresponding ones of ungrafted nylon 4 membrane. The mol ratios of adsorbed fibrinogen/albumin (F/A) of the heterografted membranes were found to decrease from 0.53 to 0.33, and the surface energy, to increase from 40.6 to 46.4 dyn/cm with the degree of grafting in the range of 12.5–29.9%, and their relationship is not remarkable for the homografted membranes for which the mol ratios of F/A are about 0.22–0.32 with the degree of grafting in the range of 14.8–103.8%. Observed from scanning electron micrographs of the membrane surface, denseness was found to be important to improve blood compatibility. Based on the dialysis permeabilities of solutes and the blood compatibility observed in this study, the homografted nylon 4/HEMA membrane can be considered as a hemodialysis material.     

Grafting of acrylamide to nylon-6 by the electron beam preirradiation technique. V. Permeability and selectivity of the grafted membranes to ionic solutes and metabolites

Nylon-6 grafted polyacrylamide (NYgAM) membranes were modified by crosslinking and/or annealing with 65% aqueous solution of formic acid at room temperature. The permselectivity properties of the treated NYgAM membranes to a number of ionic solutes of varying molecular size ranging from HBr to tetrabutylammoniumbromide (Bu₄NBr) were studied in the temperature range of 27–47°C. The temperature dependence of the permeation coefficients through the cross linked membranes indicates an apparent energy of activation of 6.6 and 11.3 kcal/mol for HBr and Bu₄NBr, respectively. In the crosslinked and annealed membranes the corresponding activation energy values were found to range from 4.4 to 5.6 kcal/mol, reflecting the increased water uptake of the annealed membranes. The flux of water and bromide solutes through the 135 μm thick crosslinked and annealed NYgAM membranes at 332% graft yield was found to be approximately equal to that of 18 μm thick cellophane films. The permeability coefficients of urea, uric acid, raffinose, and inulin through the crosslinked annealed NYgAM membranes were determined in order to establish the potential applicability of the modified membranes to clinical separation of metabolites. The flux of all four solutes, especially that of uric acid, through the modified NYgAM membranes at 100% graft yield was found to be higher than through the cellophane films. In addition, the flux of inulin was found to be strongly affected by variation in graft yields.     

The transport phenomena of some model solutes through postcrosslinked poly(2-hydroxyethyl methacrylate) membranes with different tactic precursors

Two series of membranes of various degree of hydration have been prepared by postcrosslinking highly syndiotactic and isotactic poly(2-hydroxyethyl methacrylate) [P(HEMA)] with various amounts of hexamethylene diisocyanate (HMDIC). The equilibrium water content, the partition coefficient, and the permeability of the model solutes such as urea, acetamide, NaCl, 2-propanol, and isobutanol for these membranes were measured. In addition, differential scanning calorimetry (DSC) study for the membranes was performed. The membranes of the isotactic precursor are more hydrated at 25°C compared to the ones of its syndiotactic counterpart. This may be due to the more hydrophobic nature of syndiotactic P(HEMA). The partition coefficient data show that the solutes of urea, acetamide, and NaCl are partitioned only into the water-containing region, whereas the alcohol solutes are preferentially sorbed on to polymer matrix. The permselectivity data of urea to NaCl reveal that the permselectivity of crosslinked isotactic P(HEMA), (ISO) membranes increases as the amount of HMDIC is increased from 2.5 to 10 mol %, while the trend is reversed for crosslinked syndiotactic P(HEMA), (SYN) membranes. The apparent diffusivity order of urea, acetamide, and NaCl is not the same in those two characteristic membranes: the order is urea > NaCl > acetamide for highly crosslinked ISO membranes, and NaCl > urea > acetamide for all SYN membranes, which was compared with the free diffusion data in aqueous solution and interpreted in terms of the water-structural orderlines within membranes.