Swelling Properties of Chemically Crosslinked Poly(acrylamide-co-maleic acid) Hydrogels

ABSTRACT

Chemically crosslinked poly(acrylamide-co-maleic acid) [poly(AAm-co-MA)] hydrogels were prepared by simultaneous free radical copolymerization of acrylamide (AAm) with maleic acid (MA) in presence of di or tri functional crosslinking agents using ammonium persulfate-N,N,N′,N′-tetramethylethylenediamine (APS-TMEDA) redox-initiating system. The poly(AAm-co-MA) hydrogels formation was confirmed by IR studies. The influence of crosslinkers such as N,N′-methylene-bis-acrylamide (MBA) and 2,4,6-triallyloxy-1,3,5-triazine (TATA) on swelling/de-swelling characteristics were studied in detail for poly(AAm-co-MA) hydrogels containing different amounts of maleic acid. The present investigation also deals with the influence of concentration of crosslinker and initiator on the swelling behavior of poly(AAM-co-MA) hydrogels. The effect of various salts on swelling capacity was studied. In addition, the effect of simulated biological fluids and pH solutions on the swelling of hydrogels was also studied in detail.     

聚（N-异丙基丙烯酰胺）／海藻酸钠／粘土复合水凝胶的制备及溶胀动力学研究

以无机粘土为交联剂制备了聚（N-异丙基丙烯酰胺）／海藻酸钠／粘土（PINPA／SA／Clay）复合水凝胶,通过红外光谱、X射线衍射对凝胶的结构进行了表征,结果表明：粘土的结晶结构已被破坏,粘土规整的片层被剥离并在凝胶中无序分布,起到交联剂的作用;随粘土含量的增加,凝胶网络交联密度增加,溶胀速度下降。在不同温度下对不同粘土含量的凝胶进行了溶胀动力学测试,表明在低于其相转变温度时,凝胶的扩散类型为non－Fickian扩散。     

化学交联聚乙二醇水凝胶的制备方法

对化学交联聚乙二醇基水凝胶的研究进展进行了综述.介绍了该类水凝胶的制备方法,包括几种常见的前体制备方法和常用的交联方法,并讨论了影响水凝胶溶胀性能和力学性能的几种因素.     

N-异丙基丙烯酰胺高分子水凝胶研究进展

N-异丙基丙烯酰胺基高分子水凝胶的研究进展做了综述。简要介绍了该类水凝胶的合成方法,重点分析了不同共聚单体及交联剂对水凝胶溶胀性能和环境响应性的影响,尤其是快速响应水凝胶的合成方法和N-异丙基丙烯酰胺/天然大分子水凝胶的特点。本文也简单介绍了该类水凝胶在不同领域内的应用。     

快速响应聚(N-异丙基丙烯酰胺)水凝胶的制备及性能

以N-异丙基丙烯酰胺为单体、N,N′-亚甲基双丙烯酰胺为交联剂、过硫酸铵为引发剂、N,N,N,′N′-四甲基乙二胺为加速剂,在不同浓度的羧甲基纤维素的水溶液中,在低温下聚合/交联制备了一系列快速响应的温度敏感性聚(N-异丙基丙烯酰胺)水凝胶。用SEM观察了其表面形态,测定了不同温度下达到平衡时水凝胶的溶胀比,研究了水凝胶的去溶胀动力学。结果表明,与传统水凝胶相比,该水凝胶的溶胀性能有所提高,并且对温度的变化具有较快的响应速率。以质量分数为0.75%的羧甲基纤维素水溶液中制备的水凝胶为例,该水凝胶在20℃时的溶胀比为21.4,而传统水凝胶在相同温度时的溶胀比仅为12.9;该水凝胶在1 m in内失去60%的水,在4 m in内失去约80%的水,而传统水凝胶在15 m in内仅失去66%左右的水。     

Effect of synthesis conditions on properties of poly(N-isopropylacrylamide) gels

Properties of poly(N-isopropylacrylamide) gels—equilibrium degree of swelling, shear modulus, effective crosslink density and clarity—depend significantly upon the conditions of synthesis. While it is well known that monomer and crosslinker concentrations affect gel properties, other variables are shown here to have significant effects on the properties of the resulting gels. Initiator type and concentration, synthesis temperature, mold geometry and polymerization time all significantly affect the properties, including the swelling degree. Evidence suggests that the microstructure of these gels is particularly sensitive to these variables.     

Click Crosslinked Chitosan/Gold Nanocomposite Hydrogels

Preparation of novel nanocomposite hydrogels opens up new avenues to next generation of biocompatible materials to be used in bioengineering and drug delivery. Toward this goal, chitosan nanocomposite hydrogels using click chemistry inspired cross‐linking are prepared. To enable this, Diels–Alder reaction of furan‐containing chitosan and maleimide‐coated gold nanoparticles is employed. The viscoelastic properties of the obtained nanocomposites as well as the effect of the nanoparticles as cross‐linkers are studied, indicating that they play significant role in hydrogel formation and stability. Nanoparticle‐enriched hydrogels are also found to demonstrate pH‐sensitivity therefore showing their potential for future biosensing applications.

     

N-异丙基丙烯酰胺凝胶在乙醇水溶液中的溶胀平衡

N-isopropylacrylamide (NIPAAm) was used to synthesize NIPAAm homopolymer (nonionized) and NIPAAm-sodium methacrylate copolymer (ionized). The swelling equilibria for both gels were obtained in aqueous solution of ethanol with concentration ranging from 0 to 100%(by mass) at 25℃. The swollen gel in water shrank first with the addition of a small amount of ethanol and then reswelled with further addition of ethanol showing not only a discontinuous volume phase transition but also a typical reentrant phenomenon. A thermodynamic model based on the UNIQUAC with the “free-volume“ contribution was applied to correlate and predict the swelling behavior of the poly(NIPAAM)-gels in ethanol-water mixture.     

Photopolymerization synthesis of poly(N-isopropylacrylamide) hydrogels

Poly(N-isopropylacrylamide) (NIPAAm) gels were formed by photopolymerization of NIPAAm in the absence of a crosslinker using a water solvent at 25°C. Factors affecting formation were the wavelength region of irradiated light, the type of photoinitiators, and the concentrations of the photoinitiator and monomer. A high-pressure mercury lamp (400 W) was used as a light source. An NIPAAm concentration of 10 wt % and irradiation time of 15 h was used for the photopolymerization. The gel (68% yield) was formed when the quartz glass system was used, but no gelation was observed for the Pyrex glass system that transmits light with π > 290 nm. The gel (100% yield) was easily formed, even in the latter system, when 30 mmol/L of hydrogen peroxide and potassium persulfate were used as the photoinitiator. Water soluble photoinitiators such as ferric chloride and sodium anthraquinone-2,7-disulfonate were not effective for the gel formation. Yield of the gel increased with increasing the potassium persulfate concentration (1–30 mmol/L), but it decreased when a high concentration of hydrogen peroxide (60 mmol/L) was used. The gel yield increased with the NIPAAm concentration (5–20 wt %). The degree of swelling of the resultant poly(NIPAAm) gels, which was measured by immersing the gels in water at various temperatures (0–50°C) for 24 h, steeply decreased at about 30°C with increasing temperature, exhibiting a temperature-responsive character. The gels swelled and shrank in water below and above the temperature, respectively. The extent of the character depended on the concentrations of hydrogen peroxide and monomer. The formation mechanism of the gel in the photopolymerization of NIPAAm using hydrogen peroxide photoinitiator was discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1313–1318, 1997     

聚N异丙基丙烯酰胺/黏土纳米复合自修复水凝胶的制备及性能

以N异丙基丙烯酰胺(PNIPA)为单体,纳米黏土硅酸镁锂(LXG)为交联剂,通过原位聚合反应制备了一种具有自修复功能的高分子/纳米黏土复合水凝胶。探讨了单体和黏土配比、单体与分散剂配比等参数对水凝胶成胶性能的影响。重点对该复合水凝胶自修复机理及性能进行评价。结果表明,当单体与黏土比例为1.5~2：1,单体与分散剂比例为1：10时水凝胶成胶性能良好;水凝胶的溶胀性能随黏土含量的增加而下降,最大溶胀率为12.8 g/g;合成的水凝胶在室温下无需任何修复剂,24 h即可实现损伤断面的良好修复,自修复效率最高为43.1 %。     

Swelling and Thermal Characteristics of Genipin Crosslinked Chitosan and Poly(vinyl pyrrolidone) Hydrogels

Summary Chitosan / poly(vinyl pyrrolidone) (PVP) were used to prepare semi-interpenetrating polymeric networks. The hydrogels were crosslinked using genipin, a non-toxic cross-linking agent extracted from the fruits of Gardenia jasminoides Ellis. Swelling properties of these hydrogels were studied in media of different pHs and temperatures. States of water in the swollen hydrogels at 25°C and pH 7 were determined using Differential Scanning Calorimetry (DSC). The swelling behaviour of the hydrogels was found to be dependent on the temperature and the pH of the swelling medium. The total water content in the hydrogels was found to increase with increasing PVP content.     

Glycidyl Azide Polymer Crosslinked Through Triazoles by Click Chemistry: Curing,Mechanical and Thermal Properties

Glycidyl azide polymer (GAP) was cured through “click chemistry” by reaction of the azide group with bispropargyl succinate (BPS) through a 1,3‐dipolar cycloaddition reaction to form 1,2,3‐triazole network. The properties of GAP‐based triazole networks are compared with the urethane cured GAP‐systems. The glass transition temperature (T_g), tensile strength, and modulus of the system increased with crosslink density, controlled by the azide to propargyl ratio. The triazole incorporation has a higher T_g in comparison to the GAP‐urethane system (T_g−20 °C) and the networks exhibit biphasic transitions at 61 and 88 °C. The triazole curing was studied using Differential Scanning Calorimetry (DSC) and the related kinetic parameters were helpful for predicting the cure profile at a given temperature. Density functional theory (DFT)‐based theoretical calculations implied marginal preference for 1,5‐addition over 1,4‐addition for the cycloaddition between azide and propargyl group. Thermogravimetic analysis (TG) showed better thermal stability for the GAP‐triazole and the mechanism of decomposition was elucidated using pyrolysis GC‐MS studies. The higher heat of exothermic decomposition of triazole adduct (418 kJ ⋅ mol⁻¹) against that of azide (317 kJ ⋅ mol⁻¹) and better mechanical properties of the GAP‐triazole renders it a better propellant binder than the GAP‐urethane system.     

Shedding Light on Bacterial Physiology with Click Chemistry

Bacteria constitute a major lifeform on this planet and play numerous roles in ecology, physiology, and human disease. However, conventional methods to probe their activities are limited in their ability to visualize and identify their functions in these diverse settings. In the last two decades, the application of click chemistry to label these microbes has deepened our understanding of bacterial physiology. With the development of a plethora of chemical tools that target many biological molecules, it is possible to track these microorganisms in real-time and at unprecedented resolution. Here, we review click chemistry, including bioorthogonal reactions, and their applications in imaging bacterial glycans, lipids, proteins, and nucleic acids using chemical reporters. We also highlight significant advances that have enabled biological discoveries that have heretofore remained elusive.     

N-异丙基丙烯酰胺凝胶在NaCl水溶液中溶胀行为的预测研究

In this paper,a model is presented to correlate and predict the swelling behavior of hydrogels in aqueous solutions of electrolytes.The model is a combination of VERS-model,"phantom network" theory and "free-volume"contribution.The VERS-model is used to calculate Gibbs excess energy; "phantom network" theory to describe the elastic properties of polymer network,and "free-volume" contribution to account for additional difference in the size of the species.To test the model,a series of N-isopropylacrylamide based hydrogels are synthesized by free radical polymerization in oxygen-free,deionized water at 25°C under nitrogen atmosphere.Then,the degree of swelling of all investigated gels as well as the partition of the solute between the gel phase and the surrounding coexisting liquid phase are measured in aqueous solution of sodium chloride.The model test demonstrates that the swelling behavior correlated and predicted by the model agrees with the experimental data within the experimental uncertainty.The phase transition appeared in the experiment,and the influences of the total mass fraction of polymerizable materials ξgel as well as the mole fraction of the crosslinking agent yCR on the swelling behavior of IPAAm-gels can also be predicted correctly.All these show the potential of such model for correlation and prediction of the swelling behavior of hydrogels in aqueous solutions of electrolytes.     

Swelling and Diffusion Properties of Poly(acrylamide-co-maleic acid) Hydrogels: A Study with Different Crosslinking Agents

Crosslinked hydrogels comprising acrylamide (AAm) and maleic acid (MA) were synthesized by free radical polymerization in presence of a crosslinker using ammonium persulfate (APS) and N,N,N¹,N¹-tetramethylethylenediamine (TMEDA) as initiator and activator, respectively. The crosslinked hydrogel formation was confirmed by IR analysis. The swelling/de-swelling characteristics were studied in detail for crosslinked poly(acrylamide-co-maleic acid) [poly(AAM-co-MA)] hydrogels containing different amounts of maleic acid. Four different crosslinkers such as 1,2-ethyleneglycol dimethacrylate (EGDMA), 1,4-butanediol diacrylate (BDDA), 1,6-hexanediol diacrylate (HDDA), and diallyl phthalate (DP) were utilized to study their influence on the swelling behavior of the hydrogels. The effect of reaction parameters such as the concentration of crosslinker and initiator on swelling capacity of the crosslinked poly(AAm-co-MA) hydrogels was also investigated. Further, the influence of various salts, simulated biological fluids, and pH solutions on the swelling pattern of hydrogels was studied extensively. Phase separation morphology of crosslinked hydrogels was also studied by differential scanning calorimetry. The morphology of crosslinked hydrogels were revealed using scanning electron microscopy (SEM).     

Prediction of Swelling Behavior of AT-Isopropylacrylamide Hydrogels in Aqueous Solution of Sodium Chloride

In this paper, a model is presented to correlate and predict the swelling behavior of hydrogels in aqueous solutions of electrolytes. The model is a combination of VERS-model, "phantom network" theory and "free-volume" contribution. The VERS-model is used to calculate Gibbs excess energy; "phantom network" theory to describe the elastic properties of polymer network, and "free-volume" contribution to account for additional difference in the size of the species. To test the model, a series of N-isopropylacrylamide based hydrogels are synthesized by free radical polymerization in oxygen-free, deionized water at 25℃ under nitrogen atmosphere. Then, the degree of swelling of all investigated gels as well as the partition of the solute between the gel phase and the surrounding coexisting liquid phase are measured in aqueous solution of sodium chloride. The model test demonstrates that the swelling behavior correlated and predicted by the model agrees with the experimental data within the experimental uncert     

表面强化交联聚(N-异丙基丙烯酰胺) 水凝胶的温敏和浓缩分离性能

为了提高聚(N-异丙基丙烯酰胺)(PNIPA)凝胶粒子的浓缩分离效果,以过硫酸铵/N,N,N,N,-四甲基乙二胺为引发体系,N,N′-亚甲基双丙烯酰胺(BIS)和二乙烯苯(DVB)为复合交联剂,通过反相悬浮聚合合成了表面强化交联的PNIPA凝胶粒子.考察了凝胶颗粒形态、温敏特性及其浓缩分离聚乙二醇/水性能.发现得到的凝胶为紧密珠状粒子,低临界溶解温度为32℃;随着溶质聚乙二醇相对分子质量增大或浓度减小,凝胶对聚乙二醇/水的分离效率提高;增加合成PNIPA凝胶时的BIS用量,可提高凝胶对聚乙二醇/水的分离效率,但溶胀率显著下降;增加DVB用量,分离效率大幅提高,而凝胶溶胀率基本不变.     

Poly(vinyl alcohol) Based pH Responsive Semi-IPN Hydrogels: A Comparative Swelling Investigation

The semi-interpenetrating polymer network (IPN) hydrogels composed of poly(vinyl alcohol) (PVA) and random copolymers of poly(acrylamide-co-sodium methacrylate), poly(AAm-co-NMA); poly(acrylamide-co-potassium methacrylate), poly(AAm-co-KMA); poly(acrylamide-co-maleic acid), poly(AAm-co-MA) were prepared by conventional co-polymerization employing ammonium persulphate (APS)/N,N,N¹,N¹-tetraethylmethylenediamine (TMEDA) as redox initiating system in presence of N,N¹-methylenebisacrylamide (MBA) as a crosslinker. The swelling behavior of these semi-IPN hydrogels were compared in detail in various swelling media, including different pH, salt, and biological fluids.     

含PEG组分的聚(N-异丙基丙烯酰胺)水凝胶的制备研究

首先合成了二丙烯酰基封端的聚乙二醇(PEG)大分子交联剂,然后使其与N,N-亚甲基双丙烯酰胺(BIS)和(N-异丙基丙烯酰胺)(NIPAM)单体进行交联反应,制备了PNIPAM-co-PEG-co-BIS水凝胶。与通常的PNIPAM-co-BIS凝胶比较,PNIPAM-co-PEG-co-BIS凝胶显示了明显加速的去溶胀动力学。这种加速的去溶胀性能归因于凝胶中的PEG组分为凝胶提供了亲水通道,在缩水过程中有利于凝胶的脱水。     

Permeability properties of isometrically temperature-responsive poly(acrylic acid)-graft- oligo(N-isopropylacrylamide) gel membranes

A series of temperature-responsive hydrogels were prepared by grafting oligo(N-isopropylacrylamide) (ONIPAAm) chains onto a crosslinked poly(acrylic acid) (PAAc) network, intending an application to drug delivery systems (DDS). Cloud points and swelling ratios of the obtained PAAc-graft-ONIPAAm gels were measured as a function of temperature under various pH conditions. At pH > 4.5, the clear cloud points were observed at 31–33°C, which were almost the same values as that of poly(N-isopropylacrylamide) (PNIPAAm), whereas swelling/shrinkage phenomenon was not observed in the temperature range 25–45°C. It seemed that grafted ONIPAAm chains underwent the coil-to-globule transition, while the crosslinked PAAc network remained unchanged, due to the anionic charges on the main chains. In the presence of NaCl in the buffer solution, the phase transition temperature was slightly lowered. To assess the applicability of these temperature-responsive PAAc-graft-ONIPAAm gels to DDS, permeability of theophylline through the gel membranes was measured as a function of temperature. At a temperature below the cloud point, the permeability of theophylline was low, whereas it was high at an elevated temperature above the cloud point. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1027–1034, 1998