Kinetics of water absorbency in AA/AMPS copolymers: applications of a diffusion-relaxation model

Superabsorbent copolymers, based on acrylamide, 2-acrylamido-2-methyl-propanosulfonic acid and a divinyl crosslinker, N,N′-methylenebisacrylamide, have been synthesized by free radical solution and inverse emulsion polymerization. The copolymerization has been carried at different pH values of the monomer mix reaction medium.The copolymers were characterized by their dynamic swelling behavior in deionized water, i.e. the mass of water absorbed by a sample of copolymer was measured vs time. The results were analyzed in terms of the Berens-Hopfenberg non-Fickian equation, leading to a one-only-term relaxation. These kinetics were interpreted by the diffusion-relaxation model and offer quantitative information by diffusivity at 20°C of water in the copolymers. In this investigation, the results have been confirmed within experimental error as the sample of the copolymer is swollen.     

Synthesis of Poly (Acrylamide-co-Acrylic Acid) based Superabsorbent Hydrogels: Study of Network Parameters and Swelling Behaviour

This article investigates the synthesis of superabsorbent hydrogels (SAHs) based on acrylamide and acrylic acid by solution polymerization in the presence of N,N′-methylenebisacrylamide (NMBA) as a cross-linker and potassium per sulphate as initiator. In this work the acrylamide content was varied in a large range of 30–70% (mole of total monomer) in feed, in order to study its effect on swelling behavior. The results indicate that when acrylamide content present in the hydrogels was increased from 17.23–35.85% (mole of the total monomer); then equilibrium water absorbency also increased from 276–573 (g water/g sample). But when acrylamide content was further increased from 35.85–50.24%, then equilibrium water absorbency abruptly decreased. The equilibrium water absorbency of various copolymeric hydrogels was also investigated in different concentration of saline solutions. The effect of SAHs on growth of seeds of lentil was also studied. The hydrogels were also characterized by fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM); and network parameters such as average molecular weight between cross-links (Mc) and cross-link density (q) were determined to explain the swelling behavior.     

Swelling equilibria of polymeric hydrogels containing poly(acrylamidesodiumallylsulfonate-acrylic acid)

The superabsorbent poly(AM-SAS-AA)s were synthesized to improve the water absorption capacities in comparison with the poly(AM-SAS) by an aqueous solution polymerization method from acrylamide (AM), sodium allylsulfonate (SAS), and acrylic acid (AA). The reaction conditions were controlled by varying the AA concentrations and fixing other agent concentrations to obtain the optimal superabsorbent poly(AM-SAS-AA). The poly(AM-SAS-AA) showed maximal absorption capacity at 0.3 mol/L among AA concentrations from 0.053mol/L to 0.4 mol/L. The water absorption capacities of poly(AM-SAS-AA)s prepared at the optimal reaction condition were measured within the temperature ranges from 298.15K to 318.15K. Those experimental data were used to describe the effect factors on absorption capacities and swelling equilibria data among those data were correlated with the swelling models to estimate the interchange energy parameters. Each swelling models combined with group contribution models (UNIFAC, ASOG) was introduced to calculate the swelling equilibria of water(1)/poly(AM-SAS-AA)(2) systems. The swelling behaviors could be described by the estimated parameters, and the calculated values agreed well with the experimental data.     

Synthesis of Grafted Hydrogels as Mono-Divalent Cation Exchange for Drug Delivery

pH-sensitive acrylic acid grafted polyvinylalcohol (AAc-g-PVA) hydrogels has been prepared by gamma irradiation. The maximum grafting yield was at monomer concentration 50% and dose 50 kGy. The swelling, network parameters, thermogravimetric analysis, activation energy and scanning electron microscope of the grafted hydrogels were evaluated. Hydrogel demonstrate high swelling at pH 6.8. The deswelling of the swollen gel in Ni²⁺ and Cu²⁺ cations solution was explained on the basis of mono-divalent cation exchange. The release of antihistaminic chlorphenamine maleate hydrochloride (CPM) was faster in gastric fluid (SGF) of pH 1.1 than in intestinal fluid (SIF) of pH 6.8.     

Radiation Synthesis and Characterization Study of Imprinted Hydrogels for Metal Ion Adsorption

Nickel ions were imprinted in the prepared acrylamide/citric acid P(AAm/CA) hydrogels by using gamma rays. The conditions influencing the preparation of imprinted hydrogels are optimized. The porosity and the characterization of the prepared P(AAm), P(AAm/CA), P(AAm/CA)-M hydrogels was preformed using (TGA) and (SEM). The gel content increases by increasing the monomer concentration and the irradiation dose up to 25 kGy. The swelling (%), rate constant (k), equilibrium ratio (Seq), diffusion constant (n) and the swelling behavior in response to pH value was studied. The Ni²⁺ imprinted hydrogel can considerably enhance the adsorption capacity and selectivity of the metal ion from wastewater.     

水体系中制备聚天冬氨酸高吸水性树脂的研究

以聚琥珀酰亚胺(PSI)为原料,采用无毒的γ-氨丙基三乙氧基硅烷(KH550)代替有毒的二胺类化合物作为交联剂,在水体系中合成了聚天冬氨酸高吸水性树脂,并探讨了交联剂用量、水解反应的pH值、交联温度和交联时间对高吸水性树脂吸水倍率的影响。采用红外光谱(FTIR)和扫描电镜(SEM)对高吸水性树脂进行表征。结果表明,KH550可以作为聚天冬氨酸高吸水性树脂的交联剂,且采用KH550为交联剂可以实现在水溶液中合成聚天冬氨酸。当KH550的摩尔分数是1.2%、水解反应的pH=10、交联温度为75℃、交联时间为2 h,所得产物在蒸馏水和生理盐水中的吸水倍率分别为455、115 g/g。FTIR分析表明,KH550已接枝到PSI链上,并且形成Si—O—Si结构。SEM结果显示树脂形成一种多孔的结构。     

黄原胶接枝丙烯腈制备耐盐型高吸水性树脂的研究

从提高高吸水性树脂的耐盐性出发,以硝酸铈铵为引发剂,N,N'-亚甲基双丙烯酰胺为交联剂,采用水溶液聚合法,制备了黄原胶接枝丙烯腈耐盐型高吸水性树脂.通过单因素分析法考查了引发剂用量、碱用量、聚合温度、交联剂用量等因素对产物吸水性能的影响.利用红外光谱对产物结构进行了表征.结果表明:黄原胶与丙烯腈发生了接枝聚合反应,所得树脂对蒸馏水的吸收倍率可达1156g.g-1,对0.9%NaCl溶液的吸收倍率可达518g.g-1,是一种耐盐型高吸水性树脂.预期在农业、生理卫生等领域具有较高的应用价值.     

Supramolecular Structure,Mode of Coordination,Thermal and Potentiometric Studies of Polymer Complexes: A Review

Chelating compounds derived from acryloyl monomers are being utilized as suitable ligands. They enable the formation of rigid coordination polymers. This review gives information about preparation and structurally characterization the polymer complexes by analyses, spectral techniques like IR, NMR, ESR thermal and potentiometric methods. The ESR spectral data of the Cu(II) complexes showed that the metal–ligand bonds have considerable covalent character. The thermal stability was investigated using thermogravimetric analysis. The thermal behavior of these chelates shows that the hydrated complexes lose water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The results showed that the polymer complexes are more stable than the homopolymer. Proton ligand dissociation and metal ligand stability constants of acryloyl monomers with some transition metal ions in monomeric and polymeric forms potentiometrically were determined.     

Hydrogels with Reversible Crosslinks for Improved Localised Stem Cell Retention: A Review

Successful stem cell applications could have a significant impact on the medical field, where many lives are at stake. However, the translation of stem cells to the clinic could be improved by overcoming challenges in stem cell transplantation and in vivo retention at the site of tissue damage. This review aims to showcase the most recent insights into developing hydrogels that can deliver, retain, and accommodate stem cells for tissue repair. Hydrogels can be used for tissue engineering, as their flexibility and water content makes them excellent substitutes for the native extracellular matrix. Moreover, the mechanical properties of hydrogels are highly tuneable, and recognition moieties to control cell behaviour and fate can quickly be introduced. This review covers the parameters necessary for the physicochemical design of adaptable hydrogels, the variety of (bio)materials that can be used in such hydrogels, their application in stem cell delivery and some recently developed chemistries for reversible crosslinking. Implementing physical and dynamic covalent chemistry has resulted in adaptable hydrogels that can mimic the dynamic nature of the extracellular matrix.     

反相悬浮聚合工艺制备吸水树脂及其性能研究

采用反相悬浮聚合工艺制备聚丙烯酸钠吸水树脂,研究了分散剂和搅拌转速对反相悬浮聚合体系稳定性的影响以及丙烯酸中和度、阻聚剂和交联剂对树脂吸水性能的影响.结果表明：采用聚甘油单硬脂酸酯为分散剂、搅拌转速300～450 r/min时,反相悬浮聚合体系稳定性好、制得分散性良好的均匀珠状吸水树脂;以聚乙二醇二缩水甘油酯（400）为交联剂,制得吸水树脂水溶性组分质量分数小于4%;丙烯酸中和度（摩尔分数）为80%时,树脂的吸水倍率与吸生理盐水倍率达到最大值,分别为683和68;丙烯酸中存在的阻聚剂对羟基苯甲醚不会影响树脂的吸水性能.     

吸水膨胀型聚合物堵漏剂的合成与评价

研制了一种吸水膨胀聚合物堵漏剂,该堵剂由丙烯酸（AA）、丙烯酰胺（AM）、膨润土、N,N-亚甲基双丙烯酰胺通过溶液自由基聚合法合成。并通过实验探讨了交联剂用量、引发剂用量等因素对此聚合物堵漏剂的性能的影响,获得了适宜的制备条件为：引发剂用量0.35%;m（AA）：m（AM）=3：1;单体浓度30%;膨润土加入量15%;交联剂用量0.06%;体系pH值7.0;反应温度50℃。再采用正交实验法对聚合物配方进行了优选。并将优选出的几组配方进行堵漏评价,实验结果表明,该吸水膨胀聚合物具有堵漏性能,且该聚合物具有吸液倍数大、耐盐性好、吸水后凝胶强度较好的等特点。     

Errors associated with swelling in the analysis of polymer-solvent diffusion measurements

Sorption curves are generated from a mathematical model which includes the influence of the polymer swelling for unsteady-state sorption of a vapor or liquid by a polymer. To investigate the simultaneous effects of the specific volumes of the polymer-penetrant pair and the difference between the final and initial equilibrium concentrations on the sorption curves, statistical experimental design approach is used. Simulation results obtained from the numerical solution of model equations are utilized to estimate the error that would occur if one simply evaluates the diffusion coefficient using the traditional formulas derived from the analytical solution of the sorption equation. An empirical expression is developed that describes the effects of the difference between the final and initial equilibrium concentrations and the specific volumes of the polymer and the penetrant on the magnitude of error in diffusivity associated with the use of one of these traditional formulas so called the initial slope method. The predictive ability of the regression model is tested by performing additional simulations not used in the regression analysis.     

The Effect of Mixing on the Mechanical Properties of Hyaluronan‐Based Injectable Hydrogels

A method for determining the correlation between the mixing of two reactive polymers and the structural and mechanical properties of the formed hydrogels is presented. Rheological measurements show that insufficient mixing gives rise to soft and not fully crosslinked hydrogels while excessive mixing beyond gel point results in weaker hydrogels due to potential breakage of their 3D network. Furthermore, the hydrogels swell significantly more in cell culture medium than in phosphate‐buffered saline, attributed to interactions with additional molecules such as proteins. Thus, moderate mixing gives rise to the most homogenous and mechanically stable hydrogels and the choice of medium e.g., for release experiments, should be consistent in order to avoid unnecessary variations in the data caused by different swelling profiles.

     

吸水树脂脱除重金属离子的研究

本文介绍了用超级吸水树脂（SAPC）利用离子交换和溶液吸收脱除溶液中的重金属离子，并用离子在凝胶和溶液相间分配系数（mK^d) 对其脱除能力予以比较。     

高吸水树脂对崩解型聚苯乙烯性能的影响

实验采用乳液聚合法合成了一系列单体组成和吸水倍率不同的高吸水树脂。选取部分吸水树脂与苯乙烯、表面活性剂组成聚合体系，用过氧化苯甲酰引发进行原位共混聚合，制备了遇水崩解型聚苯乙烯。同时，考察了吸水树脂的种类、添加量、吸水倍率和聚苯乙烯的摩尔质量对材料崩解性的影响。研究发现：吸水树脂添加量越大，吸水倍率越高，聚苯乙烯摩尔质量越小，越有利于材料的崩解。当吸水树脂中含有强亲水性基团时，虽然其吸水倍率没有显著提高，但却能明显改善共混物的崩解性。     

A model for the swelling of superabsorbent polymers

When dry superabsorbent polymers are immersed in water they swell by two or three orders of magnitude. Both the ultimate degree of absorption and rate of absorption are important in practical applications. Experimentally they depend on the type of polymerisation, e.g. suspension or solution; the monomer composition, e.g. proportions of acrylic acid, sodium acrylate and acrylamide; and on the type of cross-linker, e.g. water or oil-soluble. In this paper relationships between the various parameters are investigated in order to improve understanding and to identify the basic limiting factors. Plots of swelling against time have been found to fit mathematical relationships which are based on spring and dashpot models and are applied in the polymer field to viscoelastic systems. By associating the spring element with resistance to expansion by the absorbent and the dashpot element with resistance to permeation and by relating the behaviour of the elements to the polymerisation system, underlying molecular factors influencing absorption behaviour could be identified. Relationships were also established between the ultimate degree of swelling and the ratio of cross-linker to monomer for the different polymerisation systems.     

高分子物理精品课程建设

精品课程建设是衡量学校办学水平和教学质量的重要标志,是实现培养目标的基本保证。作者从教学内容、教学条件、教学方法及教学效果等方面,对高分子物理精品课程建设进行了探讨和实践。     

Recent Advances in Polymer Additive Engineering for Diagnostic and Therapeutic Hydrogels

Hydrogels are hydrophilic polymer materials that provide a wide range of physicochemical properties as well as are highly biocompatible. Biomedical researchers are adapting these materials for the ever-increasing range of design options and potential applications in diagnostics and therapeutics. Along with innovative hydrogel polymer backbone developments, designing polymer additives for these backbones has been a major contributor to the field, especially for expanding the functionality spectrum of hydrogels. For the past decade, researchers invented numerous hydrogel functionalities that emerge from the rational incorporation of additives such as nucleic acids, proteins, cells, and inorganic nanomaterials. Cases of successful commercialization of such functional hydrogels are being reported, thus driving more translational research with hydrogels. Among the many hydrogels, here we reviewed recently reported functional hydrogels incorporated with polymer additives. We focused on those that have potential in translational medicine applications which range from diagnostic sensors as well as assay and drug screening to therapeutic actuators as well as drug delivery and implant. We discussed the growing trend of facile point-of-care diagnostics and integrated smart platforms. Additionally, special emphasis was given to emerging bioinformatics functionalities stemming from the information technology field, such as DNA data storage and anti-counterfeiting strategies. We anticipate that these translational purpose-driven polymer additive research studies will continue to advance the field of functional hydrogel engineering.