Superabsorbent materials derived from hydroxyethyl cellulose and bentonite: Preparation,characterization and swelling capacities

Superabsorbent polymers (SAPs) and composites (SAPCs) were prepared entirely by graft copolymerization of polyacrylamide (PAM) onto hydroxyethyl cellulose (HEC), using potassium persulfate (KPS) as an initiator, and N,N′-methylenebisacrylamide (MBA) as a crosslinker, in an aqueous solution. The extent of grafting was evaluated from % grafting efficiency (%GE) for various HEC/AM ratios, and a near optimal ratio was determined. Influences of various preparation parameters, i.e., the ratio of HEC/AM, amount of initiator and crosslinker, reaction temperature and time, and amount of filler on water swelling capacity of SAPs and SAPCs were studied. An FT-IR determination confirmed that the PAM was successfully grafted onto the HEC backbone, by showing absorption bands of the HEC backbone and new absorption bands from the grafted copolymer. The swelling capacity of SAPs and SAPCs depended strongly on different parameters, and the maximum swelling capacity was over 426 g/g and 538 g/g for the SAPs and SAPCs, respectively.     

碳纳米管复合聚丙烯酸钠的制备及吸水性能

以过硫酸铵(APS)为引发剂,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,采用水溶液聚合法制备了碳纳米管/聚丙烯酸钠高吸水树脂。系统考察了碳纳米管质量分数、引发剂、交联剂和聚合温度对树脂吸水性能的影响。结果表明,以单体丙烯酸质量为基准,当交联剂,引发剂和碳纳米管质量分数分别为0.04%、0.3%和0.3%,聚合温度75℃时,所合成树脂的吸水性能最佳。添加碳纳米管后树脂表面粗糙和形成孔结构导致了其吸水性能的变化,使得碳纳米管/聚丙烯酸钠的吸水量和吸水速率明显提高,其吸去离子水和生理盐水能力分别达到1423和104g/g。该树脂重复吸水5次后,其吸水能力为1081.5g/g,达到最大吸水倍数的76.0%。     

Modified chitosan 4. Superabsorbent hydrogels from poly(acrylic acid-co-acrylamide) grafted chitosan with salt- and pH-responsiveness properties

Graft copolymerization of mixtures of acrylic acid (AA) and acrylamide (AAm) onto chitosan was carried out by using potassium persulfate (KPS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. The effect of reaction variables, such as MBA concentration and AA/AAm ratio on the water absorbency capacity have been investigated. The polymer structures were confirmed by FTIR spectroscopy. Water absorbencies were compared for the hydrogels before and after alkaline hydrolysis. In the non-hydrolyzed hydrogel, enhanced water absorbency was obtained with increasing AA in monomer feed. However, after saponification, the sample with high AAm ratio exhibited more water absorbency. These behaviors were discussed according to structural parameters. The swelling kinetics of the superabsorbing hydrogels was studied as well. The hydrogels exhibited ampholytic and reversible pH-responsiveness characteristics. The swelling variations were explained according to swelling theory based on the hydrogel chemical structure. The hydrogels exhibited salt-sensitivity and cation exchange properties. The pH-reversibility and on-off switching properties of the hydrogels make the intelligent polymers as good candidates for considering as potential carriers for bioactive agents, e.g. drugs.     

Kinetics and mechanism of emulsifier-free emulsion polymerization. III. Styrene/nonionic comonomer (2-hydroxyethyl methacrylate) system

The emulsifier-free emulsion polymerizations of styrene in the presence of about 0.33–2.7% (relative to styrene) of the water soluble comonomer, 2-hydroxyethyl methacrylate (HEMA), and of the initiator, potassium persulfate (KPS), were carried out. It was found that KPS plays a predominant role in the particle nucleation process, since the number density of polymer particles (N_p) was dependent on the 0.97-power of [KPS]. The nucleation ability of HEMA was weak, since N_p was dependent only on the 0.17-power of [HEMA]. The particle nucleation stage ceased quite early before 1% conversion, leading to nearly monodispersed polymer particles. The nucleation is suggested to be via the homogeneous nucleation mechanism. The particles grow via the core-shell structure mechanism (shell region polymerization), since the particle size is rather large—from 1500 to 6000 Å. The amount of HEMA can affect the shell thickness and physical properties of the shell, such as the monomer swelling capacity and monomer diffusion rate.     

粉煤灰复合聚丙烯酸钠凝胶的制备及其溶胀性能

粉煤灰(CFA)存在的情况下,采用自由基溶液聚合法,以过硫酸钾(KPS)为引发剂,N,N'-亚甲基双丙烯酰胺(NNMBA)为交联剂,制备了粉煤灰复合聚丙烯酸钠凝胶(CFAPAANa)。 以丙烯酸单体质量为基准,当交联剂用量为0.08%,引发剂用量为0.4%,粉煤灰用量为3%,丙烯酸中和度为70%,聚合温度为70 ℃时,所合成的粉煤灰复合聚丙烯酸钠凝胶在蒸馏水和生理盐水中平衡溶胀比最高,分别为1556(g/g)和168(g/g)。 考察了复合凝胶在不同介质溶液中的溶胀动力学,保水性能以及在土壤中的降解行为。 溶胀动力学研究表明,蒸馏水中溶胀初期复合凝胶聚合物链段的扩散运动能够调控凝胶溶胀的快慢及程度,而生理盐水中水分子的平移和对流运动在凝胶的溶胀过程中起着关键性作用。 保水和降解实验结果表明,25 ℃时,50 h凝胶保水率为64%,土壤中50 d时降解率达60%。 相比于聚丙烯酸钠凝胶,粉煤灰复合凝胶保水率提高了8%。     

Characterization and Evaluation of Acrylic Acid Co-2-acrylamido-2-methylpropane-1-sulfonic Acid Hydrogels for Uranium Recovery

Crosslinked 2-acrylamido-2-methyl-1-propane sulfonic acid -co- acrylic acid (AMPS/AA) hydrogels were synthesized by radical polymerization in the presence of N,N′-methylenebisacrylamide (MBA) as the crosslinking agent using potassium persulfate (KPS) as initiator. Hydrogels with different compositions and crosslinker concentrations were prepared. The structures of hydrogels were characterized by FTIR analysis. Thermal stabilities of the hydrogels were investigated using TGA and DSC analysis. Swelling kinetics and the equilibrium water content (EWC) of the hydrogels were studied. The swelling behavior of these hydrogels was investigated at different pHs at room temperature. Also the swelling behavior of these hydrogels was investigated at different ionic strength. The ability of the prepared hydrogels to bind uranium(VI) was tested under noncompetitive conditions by batch equilibrium procedure. Experimental work using uranyl nitrate hexahydrate bought from the local market was carried out in the safeguards destructive analysis laboratory (KMP-I) in the National Center for Nuclear Safety and Radiation Control.     

Preparation and characterization of poly(acrylic acid)‐iron rich smectite superabsorbent composites

A novel poly(acrylic acid)‐iron rich smectite (IRS) superabsorbent composite was synthesized by graft copolymerization reaction of acrylic acid (AA) in the presence of N,N‐methylenebisacrylamide (MBA) as a crosslinker. IRS was used to strengthen the hydrogel products in the polymerization process. Water absorbencies for these superabsorbent composites in water and saline solutions were investigated. IRS caused a reduced equilibrium swelling as low as 8–26%. However, grafted IRS particles resulted in improved gel strength as high as 66% compared to the IRS‐free sample. IRS modified superabsorbent hydrogel composites exhibited higher thermal stability compared to the IRS‐free sample. The pH dependent reversible swelling behavior of hydrogels was also investigated. It is found that the swelling process is pH dependent and reversible for synthesized superabsorbent. Superabsorbent hydrogel composites were characterized by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). FTIR spectroscopy was confirmed grafting of acrylic chains onto the surface of IRS particles. From the standpoint of these results, these strengthened and thermostabilized hydrogels may be considered as good candidates for a controlled release study and agricultural applications. Copyright © 2007 John Wiley & Sons, Ltd.     

均相条件下甲壳素基高吸水树脂的制备及性能研究

利用冻融循环处理破坏甲壳素致密的晶体结构和氢键相互作用,使甲壳素溶解在8 wt%NaOH/4wt%urea水溶液中,制备了碱-甲壳素均相溶液.采用静态溶液聚合法,以过硫酸铵(APS)为引发剂、甲叉双丙烯酰胺(MBA)为交联剂,在均相条件下制备了甲壳素接枝聚丙烯酸钠高吸水树脂.研究了丙烯酸、NaOH、MBA和APS用量以及反应温度和时间对产物吸水性能和得率的影响.在最优化条件下制备的树脂的最大吸蒸馏水、自来水、生理盐水和人工尿液倍率分别可达1251,455,84和77 g.g-1.采用FTIR和XRD对合成的树脂进行初步结构表征,证明反应过程中甲壳素与丙烯酸发生了接枝共聚反应,而不是甲壳素与聚丙烯酸钠的简单物理共混.     

Timolol maleate release from pH-sensible poly(2-hydroxyethyl methacrylate-co-methacrylic acid) hydrogels

Multifunctional polymeric materials were obtained from poly(methacrylic acid-co-2-hydroxyethyl methacrylate), to be used as a raw material in the manufacture of contact lens and as drug delivery systems. Poly(methacrylic acid-co-2-hydroxyethyl methacrylate) was prepared by free-radical polymerization in aqueous solution at 60 °C using potassium persulfate (KPS) as initiator and N,N^′-methylenebisacrylamide (BIS) as cross-linker agent. The dynamic and equilibrium swelling properties of dry glassy poly(methacrylic acid-co-2-hydroxyethyl methacrylate) polymeric networks were studied as a function of pH and methacrylic acid (MAA) content. The water content increase as MAA content and pH increase. Timolol maleate delivery from poly(MAA) and poly(2-hydroxyethyl methacrylate) (HEMA) homopolymers was studied and the results show a Fickian diffusion behavior.     

多孔壳聚糖接枝聚丙烯酸/钠基蒙脱土复合高吸水凝胶的制备及其对Pb2+的吸附

以十二烷基苯磺酸钠(SDS)胶束为孔模板,过硫酸铵(APS)引发,N,N'-亚甲基双丙烯酰胺(MBA)交联,壳聚糖(CS)与丙烯酸(AA)、钠基蒙脱土(Na-MMT)在水溶液中接枝共聚,成功制备了多孔壳聚糖接枝聚丙烯酸/钠基蒙脱土(CS-g-PAA/Na-MMT)复合高吸水凝胶,提出了SDS胶束致孔机理。扫描电子显微镜(SEM)分析表明,添加SDS的样品,凝胶表面出现多孔结构。通过考察SDS浓度对复合高吸水凝胶平衡吸水倍率和吸水速率的影响,发现当SDS浓度为1.5 mmol/L时,复合凝胶在蒸馏水和生理盐水中的平衡吸水倍率相对于空白样分别提高53.9%和35.3%,初始溶胀速率常数K_is也由空白样的1.2652 g/(g·s) 提高到5.1680 g/(g·s)。多孔结构也使复合凝胶对Pb²⁺的吸附速率加快,在10 min内即可达到饱和吸附量的95%,30 min完全达到吸附平衡。     

不同交联剂对甲基丙烯酸-β-羟乙酯/E-51双甲基丙烯酸酯聚合物水凝胶性能的影响

以水溶性单体甲基丙烯酸-β-羟乙酯(HEMA)与大分子交联剂E-51双甲基丙烯酸酯(E-51-DMA)(质量比HEMA/E-51-DMA=90/10)为主要原料,分别引入了5种小分子交联剂:N,N′-亚甲基双丙烯酰胺(MBA)、二乙烯基苯(DVB)、双甲基丙烯酸乙二醇酯(EDMA)、1,1,1-三(丙烯酰氧甲基)丙烷(TAP)和2,2,2-三(丙烯酰氧甲基)乙醇(TAE),采用本体聚合方法合成了5个系列的聚合物水凝胶.研究了小分子交联剂的类型及用量对水凝胶溶胀性能、杨氏模量以及有效交联密度ve和聚合物-水相互作用参数χ的影响,并比较了不同交联剂的交联效率.结果表明,随着小分子交联剂用量的增大,水凝胶平衡含水量EWC逐渐降低,聚合物体积分数2逐渐增大,反映聚合物网络结构的有效交联密度ve以及热力学参数聚合物-水相互作用参数χ值也随之增大.通过理论交联密度和有效交联密度的线性拟合,得到所选用的5种小分子交联剂在E-51-DMA10/HEMA90水凝胶体系中的交联效率,其顺序为DVB>EDMA>TAE>MBA≈TAP.     

Preparation,swelling, and stimuli‐responsive characteristics of superabsorbent nanocomposites based on carboxymethyl cellulose and rectorite

Utilization of naturally available raw materials for the fabrication of eco‐friendly functional materials has long been desired. In this work, a series of superabsorbent nanocomposites were prepared by radical solution copolymerization of sodium carboxymethyl cellulose (CMC), partially neutralized acrylic acid (NaA), and rectorite (REC) in the presence of initiator ammonium persulfate (APS) and crosslinker N,N'‐methylene‐bis‐acrylamide (MBA). The optimal reaction variables including the mass ratio of acrylic acid (AA) to CMC, MBA concentration, and REC content were explored. FTIR spectra confirmed that NaA had been grafted onto CMC and REC participated in polymerization. REC was exfoliated and uniformly dispersed in the CMC‐g‐PNaA matrix without agglomeration as shown by XRD, TEM, and SEM analysis. The thermal stability, swelling capabilities, and rate of the nanocomposites were improved after introducing REC, and the gel strength greatly depended on the concentration of crosslinker MBA. The nanocomposite showed excellent responsive properties and reversible On–Off switching characteristics in various saline, pH, and hydrophilic organic solvent/water solutions, which provided great possibility to extend the application domain of the superabsorbent nanocomposites such as drug delivery system. Copyright © 2010 John Wiley & Sons, Ltd.     

PAAM高吸水树脂反相悬浮聚合

采用反相悬浮聚合法,通过部分中和丙烯酸与丙烯酰胺共聚制备了聚(丙烯酸-丙烯酰胺)(PAAM)高吸水树脂,讨论了聚合过程主要影响因素对其吸液性能的影响,并对其进行了FTIR、TGA测试,得到最佳的合成工艺配方:单体质量浓度为30%,中和度N为75%,丙烯酸与丙烯酰胺的摩尔比为7∶3,交联剂、引发剂和分散剂质量浓度分别为0.065%、0.7%和0.5%(相对于单体总质量),单体溶液的滴加速度为2～3mL/min,聚合温度和时间分别为70℃和1.5h。此时在蒸馏水、0.9%NaCl溶液%(wt)中最大吸水倍率分别为Qw=1300g/g、Qs=93g/g(Qw为蒸馏水中吸水倍率,Qs为0.9%NaCl溶液中的吸水倍率,下同),树脂在320℃之前都是比较稳定的,可以适应较高的使用温度。     

Synthesis and characteristic of the thermo- and pH-sensitive hydrogel and microporous hydrogel induced by the NP-10 aqueous two-phase system

A series of novel thermo- and pH-sensitive (NP10-AA TPS) hydrogels and microporous (NP10-AA MP) hydrogels, inducing by polyoxyethylene (10) nonyl phenyl ether (NP-10) aqueous two-phase system, was designed and fabricated with acrylic acid (AA) as the monomer for the first time. The resultant NP10-AA TPS hydrogel, compared with the traditional TPS hydrogel, was more advanced in both of the high swelling ratio and the variable lower critical solution temperature (LCST). A simple synthesis technique of the NP10-AA MP hydrogel was developed. The thermo-sensitivity of the NP10-AA TPS hydrogel including the initial swelling ratio, LCST, dehydrated efficiency, was depended strongly on the crosslinker (MBA), initiator (APS), NP-10 and AA concentration. The swelling rate of the NP10-AA MP hydrogel was much higher than that of AA hydrogel dehydrated in the same lyophilization condition.     

甲基丙烯酸2-羟乙酯水溶液聚合与硫氰化钠的效应

<正> 甲基丙烯酸2-羟乙酯(HEMA)是一带有羟基的功能性单体,它可以在自由基聚合引发剂如过氧化苯甲酰、偶氮二异丁腈、过氧化二碳酸二异丙酯或氧化还原引发体系过硫酸盐-乙酸二甲胺基乙酯的作用下进行自由基聚合,我们已报道带有羟基的单体如HEMA、甲基丙烯酸羟丙酯(HPMA)及甲基丙烯酯3-甲氧基-2-羟丙酯(MHPMA)可用     

Preparation of carboxymethyl cellulose‐g‐poly (acrylamide)/montmorillonite superabsorbent composite as a slow‐release urea fertilizer

A superabsorbent composite was synthesized through free‐radical graft copolymerization of carboxymethyl cellulose, acrylamide, and montmorillonite by means of a crosslinker such as N,N′‐methylenebisacrylamide and potassium persulfate as an initiator. The preparation mechanism was proposed, and the composite structures were confirmed by using Fourier transform infrared spectroscopy, X‐ray diffraction, thermal gravimetric analysis, and scanning electron microscope. The factors influencing the swelling capacity of the composite were determined to accomplish the highly swelling capacity. The composition (15 wt% carboxymethyl cellulose, 5.4 wt% montmorillonite, 82 wt% acrylamide, 0.07 wt% N,N′‐methylenebisacrylamide, and 1.1 wt% potassium persulfate) exhibited high swelling capacity; it was selected to be loaded with urea fertilizer, and the release was investigated by measuring the conductivity. The results showed that the new controlled release system has good slow release properties.     

Experimental study of albumin and lysozyme adsorption onto acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) surfaces

Many commercial soft contact lenses are based on poly-2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA) hydrogels. The adsorption of proteins, albumin and lysozyme, on such contact lens surfaces may cause problems in their applications. In this work the adsorption of proteins, albumin and lysozyme, on hydrogel surfaces, AA and HEMA, was investigated as a function of concentration of protein. Also the effects of pH and ionic strength of protein solution on the adsorption of protein were examined. The obtained results indicated that the degree of adsorption of protein increased with the concentration of protein, and the adsorption of albumin on HEMA surface at the studied pHs (6.2-8.6) was higher than AA surface, whereas the adsorption of lysozyme on AA surface at the same pHs was higher than HEMA. The change in ionic strength of protein solution affected the proteins adsorption on both AA and HEMA surfaces. Also, the amount of sodium ions deposited on the AA surface was much higher than HEMA surface. This effect can be related to the negative surface charge of AA and its higher tendency for adsorption of sodium ions compared to the HEMA surface.     

Preparation and Properties of Biodegradable Slow-Release PAA Superabsorbent Matrixes for Phosphorus Fertilizers

Biodegradable superabsorbent matrixes for a slow-release fertilizer were prepared by using crosslinked acrylic acid and water-soluble granular phosphorus fertilizer KH₂PO₄. The effects of the amount of crosslinker, initiator and phosphorus fertilizer concentration on water absorption were investigated and optimized. The products show excellent slow release and water-retention capacity, being nontoxic in soil and environment-friendly, and could be useful especially in agricultural and horticultural applications. The results showed that the hydrogel structure and swelling capacity was affected by various factors, such as concentration of crosslinker and initiator, as well as by the amount of KH₂PO₄.     

Copolymerization and Properties of Multicomponent Crosslinked Hydrogels

A series of multicomponent hydrogels were prepared by the copolymerization of hydrophobic silicon-containing monomer 3-bis(trimethylsilyloxy) methylsilylpropyl glycerol methacrylate(Si MA) with the solvent-responsive monomers 2-hydroxyethyl methacrylate(HEMA) and N-vinyl pyrrolidone(NVP) and thermosensitive monomer N,N-dimethyl acrylamide(DMA). 2-Hydroxy-2-methyl phenyl acetone(D-1173) was chosen as UV initiator and five different dienes/triene monomers were selected as crosslinking agent in order to select the best crosslinker. The ethanol extraction experiments as well as the FTIR, DSC and TG results showed that the copolymerization was effective. The optical, permeability, and mechanical analysis results demonstrated that the obtained hydrogels were highly transparent with good oxygen permeability and mechanical properties. And the impact of crosslinker on the mechanical properties of the hydrogels was also discussed in detail. The basic results demonstrated that the obtained hydrogels had good stimuli-responsive effects to both p H value and solvent.     

Taguchi optimized synthesis of collagen-g-poly(acrylic acid)/kaolin composite superabsorbent hydrogel

A novel biopolymer-based hydrogel composite was synthesized through chemical crosslinking by graft copolymerization of partially neutralized acrylic acid onto the hydrolyzed collagen. The Taguchi method, a robust experimental design, was employed for the optimization of the synthesis based on the swelling capacity of the hydrogels. This method was applied for the experiments and standard L16 orthogonal array with five factors and four levels. In the synthesis of the composite superabsorbent, N,N′-methylene bisacrylamide (MBA) as crosslinker, ammonium persulfate (APS) as initiator, acrylic acid (AA) as monomer, neutralization percent (NU), and collagen/kaolin weight ratio were used as important factors. From the analysis of variance of the test results, the most effective factor controlling equilibrium swelling capacity was obtained and maximum water absorbency of the optimized final product was found to be 674 g/g. The surface morphology of the gel was examined using scanning electron microscopy. Furthermore in this research, swollen gel strength of composite SAPs already swollen under realistic conditions (saline solution absorbency under load) was determined.