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。     

温度及pH敏感共聚/粘土纳米复合水凝胶的合成与性能研究

以无机粘土为交联剂制备了具有温度、pH双重敏感性的聚（N-异丙基丙烯酰胺-co-甲基丙烯酸-β-羟乙酯）/粘土纳米复合水凝胶（P（NIPA-co-HEMA）/clay）,并用红外和X衍射对其结构和形态进行了表征。在弱碱性（pH=7.4）和25℃条件下,分别研究了温度和不同pH缓冲溶液对该凝胶溶胀度的影响,测定了纳米复合水凝胶的力学性能。结果表明：水凝胶的粘土已被剥离成单片层,且均匀分散在凝胶网络中,起交联作用;P（NIPA-co-HEMA）/clay具有良好的温度、pH双重敏感特性;凝胶的断裂伸长率〉1000%。     

纳米铜碳/海藻酸钠复合水凝胶的制备及性能

以吸附了硫酸铜的天然棉纤维为原料,高温热解制备纳米铜碳复合材料(NCCC),并利用原位释放法以二价钙离子为交联剂制备出纳米铜碳复合材料/海藻酸钠(NCCC/SA)复合水凝胶,来缓释抑藻材料NCCC。调节CaCO₃/SA的质量比,考察海藻酸钠水凝胶的力学性能、溶胀和降解性能来优选凝胶载体。调节NCCC/SA质量比,考察NCCC/SA复合水凝胶力学性能、溶胀和降解性能。NCCC/SA质量比越大,复合水凝胶的力学性能越差,但其溶胀和降解性能几乎没有影响。为了应对动态水环境的使用要求,最终选用CaCO₃/SA的质量比为18.18%的海藻酸钠水凝胶为载体,NCCC/SA质量比为2∶1来制备复合水凝胶,并模拟NCCC的缓释,为NCCC应用于抑藻的研究奠定了理论基础。     

γ–聚谷氨酸/海藻酸钠双网络水凝胶的制备及性能研究

采用两步法合成了γ–聚谷氨酸（PGA）/海藻酸钠（SA）双网络水凝胶,其中化学交联的PGA–Ly（赖氨酸）网络作为第一网络,而离子交联的SA–Ca2＋网络作为第二网络。通过控制水凝胶的弹性张力和溶胀率之间的平衡,很好地控制了PGA/SA水凝胶的溶胀。通过傅里叶变换红外光谱（FTIR）对水凝胶结构进行了表征。压缩试验结果表明,PGA/SA水凝胶的压缩模量（0.17 MPa）为PGA水凝胶（0.034MPa）的5倍。拉伸试验结果显示,当SA质量浓度达到0.02 g/m L时,PGA/SA水凝胶的断裂伸长率和拉伸强度分别为PGA水凝胶的2倍和8倍。溶胀试验结果表明,随SA含量增加,水凝胶溶胀率逐渐下降。这些特性表明PGA/SA水凝胶在组织工程中具有巨大的应用潜力。     

酸增强CMC/AA/CB[8]/ATP水凝胶的制备及吸附性能研究

采用八元瓜环、凹凸棒黏土为双交联剂制备一种综合性能优异的羧甲基纤维素/丙烯酸/八元瓜环/凹凸棒黏土水凝胶(CMC/AA/CB[8]/ATP水凝胶),采用FT-IR、SEM技术对该凝胶结构进行表征,分析其溶胀规律,并对其力学性能以及吸附性能进行研究.结果表明:CMC与AA接枝共聚形成长链,CB[8]和ATP分别以氢键与A...     

N-异丙基丙烯酰胺pH敏感型水凝胶的制备及对甲基紫吸附性能研究

以N-异丙基丙烯酰胺和海藻酸钠(SA)为主要原料,制备了具有pH敏感型的智能水凝胶。探究了不同海藻酸钠、引发剂、交联剂等配比的凝胶在不同pH值环境下的溶胀性能,并对制备的凝胶进行甲基紫的吸附性能测试。结果表明:碱性条件下,凝胶溶胀度随SA用量的增加而增大,酸性条件下则相反;凝胶的溶胀度随交联剂用量的增加而减小;引发剂用量为3%时凝胶的溶胀度较高;凝胶在适宜条件下对甲基紫溶液有良好的吸附性能。     

聚丙烯酸镁/丙烯酸钠双交联水凝胶的制备及性能研究

以丙烯酸镁(Mg A)和丙烯酸钠(SA)为单体、N,N'-亚甲基双丙烯酰胺(MBA)为共价交联剂,通过溶液聚合方法制备了系列聚丙烯酸镁/丙烯酸钠(PAMgA/x-PASA)双交联水凝胶,并测试分析了共聚水凝胶材料的结构、吸水特性和力学性能。结果表明,MBA作用下丙烯酸镁和丙烯酸钠形成了双交联结构的共聚水凝胶,显著提高了丙烯酸盐水凝胶的吸水溶胀比、保水性和重复吸水能力。当SA质量分数为20%时,水凝胶的吸水溶胀比达550%,较单一离子交联的聚丙烯酸镁提高近4倍; 12 h干燥后的保水率约60%;而多次干燥-吸水溶胀以后,水凝胶的吸水溶胀比仍高达300%。此外,丙烯酸钠和MBA的加入对水凝胶的拉伸强度影响不大,但显著提高了材料的断裂伸长率,可从395%提高到690%。     

新型聚丙烯酰胺凝胶制备、表征及强度和溶胀性能研究

以丙烯酰胺(AM)为单体,对二乙烯苯(p-DVB)为交联剂,过硫酸铵(APS)为引发剂,采用自由基溶液聚合的方法合成了交联聚丙烯酰胺凝胶。利用红外对其结构进行了表征;测定了水凝胶的力学性能和溶胀特性,并分别与目前广泛应用的BIS交联的水凝胶进行对比。研究表明,以含苯环结构的p-DVB代替BIS作为交联剂能够提高交联聚丙烯酰胺凝胶的力学强度和溶胀性能,当单体浓度为15%,交联剂浓度为1%时,p-DVB交联的水凝胶压缩强度接近1 MPa,25℃时的平衡溶胀比达到40 g/g。     

半纤维素/碳纳米管复合凝胶的溶胀性能

采用 (NH4)2S2O8-Na2SO3为引发剂体系,N,N-亚甲基双丙烯酰胺（BIS）为交联剂,利用自由基聚合法成功制备了半纤维素/碳纳米管复合凝胶。用SEM对凝胶的结构形态进行了研究分析;研究了单体比例、碳纳米管含量和pH值对凝胶溶胀率的影响;并应用溶胀动力学方程对试验数据进行拟合。研究结果表明：半纤维素/碳纳米管复合凝胶的溶胀率随着甲基丙烯酸/半纤维素比例的增加而减小,随着碳纳米管含量的增加而减小;pH≤11时随pH值的增加而增大,pH>11时随pH值的增加而减小。拟合结果表明整个溶胀过程符合Schott二级动力学模型。     

三甲基壳聚糖季铵盐水凝胶的制备及性能

采用反应活性强和交联条件温和的二乙烯基砜为交联剂,制备了N,N,N-三甲基壳聚糖季铵盐水凝胶（TMCG）并研究了TMCG的溶胀行为、水的状态和分布以及力学性能等。结果表明,TMCG在水中溶胀迅速,平衡溶胀度达40倍,并且具有离子响应性;水分子在TMCG中以自由水、可冻结的结合水和非冻结的结合水三种形式存在,其非冻结的结合水含量随交联剂浓度的增加而增大。TMCG具有良好的力学性能,拉伸强度达13.8 MPa,断裂伸长率达135.3%。     

Semi‐IPN carrageenan‐based nanocomposite hydrogels: Synthesis and swelling behavior

Inclusion of nano‐clays into hydrogels is an efficient approach to produce nanocomposite hydrogels. The introduction of nano‐clay into hydrogels causes an increase in water absorbency. In the present work, Nanocomposite hydrogels based on kappa‐carrageenan were synthesized using sodium montmorillonite as nano‐clay. Acrylamide and methylenebisacrylamide were used as monomer and crosslinker, respectively. The structure of nanocomposite hydrogels was investigated by XRD and SEM techniques. Swelling behavior of nanocomposite hydrogels was studied by varying clay and carrageenan contents as well as methylenebisacrylamide concentration. An optimum swelling capacity was achieved at 12% of sodium montmorilonite. The swollen nanocomposite hydrogels were used to study water retention capacity (WRC) under heating. The results revealed an increase in WRC due to inclusion of sodium montmorilonite clay. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of sodium alginate/poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide)/clay semi-IPN magnetic hydrogels

pH- and temperature-responsive semi-interpenetrating magnetic nanocomposite hydrogels (NC hydrogels) were prepared by using linear sodium alginate (SA), poly(N-isopropylacrylamide) (PNIPAM) and Fe₃O₄ nanoparticles with inorganic clay as an effective multifunctional cross-linker. The effects of cross-linker and SA contents on various physical properties were investigated. The NC hydrogels exhibited a volume phase transition temperature (VPTT) around 32 °C with no significant deviation from the conventional chemically cross-linked PNIPAM hydrogels (OR hydrogels). The swelling ratios of NC hydrogels were much larger than those of OR hydrogels. Moreover, the swelling ratios of NC hydrogels gradually decreased with increasing the contents of clay and increased with increasing the contents of SA. The pH sensitivity of NC hydrogels was evident below their VPTT. The NC hydrogels had a much better mechanical property than the OR hydrogels. The results showed that the incorporation of clay did not affect the saturation magnetization of the hydrogels.     

Robust and thermo-response graphene–PNIPAm hybrid hydrogels reinforced by hectorite clay

Graphene oxide (GO) based hydrogels were proposed to be used as biomaterials and stimuli-response materials, but their poor mechanical properties restricted their applications. We enhanced GO–poly(N-isopropylacrylamide) (PNIPAm) hydrogels by hybrid with the hectorite clay through in situ polymerization for the first time. This clay was found to stabilize the GO in the aqueous suspension when a reducer was added in a redox initiating pair. These GO–clay–PNIPAm hybrid hydrogels exhibited a high mechanical strength and extensibility with the GO sheets as the cross-linker and with the hectorite clay as both the cross-linker and reinforcing agent. They were thermal-responsive with the volume phase transition at ∼34 °C. Reduction of the GO with l-ascorbic acid under environmental friendly conditions resulted in a high conductivity to the graphene–clay–PNIPAm hydrogels. These graphene–clay–PNIPAm hydrogels still had desirable mechanical properties. This finding has provided an easy method to prepare strong and stimuli-response graphene–polymer hydrogels to meet the demand for the newly developed soft matter.     

Equilibrium swelling behavior and elastic properties of polymer–clay nanocomposite hydrogels

Nanocomposite hydrogels were prepared by free‐radical polymerization of the monomers acrylamide (AAm), N,N‐dimethylacrylamide (DMA), and N‐isopropylacrylamide (NIPA) in aqueous clay dispersions at 21°C. Laponite XLS was used as clay nanoparticles in the hydrogel preparation. The hydrogels based on DMA or NIPA monomers exhibit much larger moduli of elasticity compared with the hydrogels based on AAm monomer. Calculations using the theory of rubber elasticity reveal that, in DMA‐clay or NIPA‐clay nanocomposites, both the effective crosslink density of the hydrogels and the functionality of the clay particles rapidly increase with increasing amount of Laponite up to 10% (w/v). The results suggest that DMA‐clay and NIPA‐clay attractive interactions are stronger than AAm‐clay interactions due to the formation of multiple layers on the nanoparticles through hydrophobic associations. It was also shown that, although the nanocomposite hydrogels do not dissolve in good solvents such as water, they dissolve in dilute aqueous solutions of acetone or poly(ethylene oxide) of molecular weight 10,000 g/mol, demonstrating the physical nature of the crosslink points. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Study on a new polymer/graphene oxide/clay double network hydrogel with improved response rate and mechanical properties

pH‐ and temperature‐responsive double network hydrogels (DN hydrogels) were prepared by using poly (N‐isopropylacrylamide) (PNIPAM) as a tightly crosslinked network (1st network), polyacrylic acid (PAA) as a loosely crosslinked network (2nd network), with clay and graphene oxide as effective crosslinkers and reinforcing fillers. The structure and morphology of the hydrogels were characterized by SEM, FTIR, DSC, and TGA. The synergetic effects of clay, GO and DN structure on various physical properties were investigated. With the increasing of crosslinking densities, the swelling ratios of DN hydrogels gradually decreased by increasing the contents of graphene oxide and PAA. While the DN hydrogels had much better mechanical properties than that of the conventional chemically cross‐linked PNIPAM hydrogels. POLYM. ENG. SCI., 55:1361–1366, 2015. © 2015 Society of Plastics Engineers     

Hydrogels reinforced with nanoclays with improved response rate

Two series of semiinterpenetrating networks (SIPN) based on linear hydrophilic poly(vinyl alcohol) (PVA) and thermo‐responsive poly(N‐isopropylacrylamide) (PNIPA), physically crosslinked with inorganic clay, are presented. The hydrogels with different crosslinking densities were prepared by varying the content of clay from 1 to 6 wt % and contained linear interpenetrant, PVA in the range of 0.5–1.5 wt %. The effect of clay content on swelling/deswelling behavior and phase transition in PNIPA gels, as well as the feasibility of reinforcing the gels with high molecular weight PVA, were analyzed. The thermal response of hydrogels, followed by DSC, confirmed that the insertion of hydrophilic PVA did not have a significant effect on the onset of the volume phase transition temperature, while the response was faster. The equilibrium degree of swelling of SIPNs and PNIPA hydrogels was in the range of 9–79 and decreased with increasing content of clay. The internal morphology and surface wettability of the hydrogels were investigated by scanning electron microscope analysis and contact angle measurements, respectively. The network structural parameters of the PNIPA and SIPN nanocomposites hydrogels, such as the average molecular weight between crosslinks, M_c, and effective crosslinking density, N_e, were determined by dynamic mechanical analysis. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44535.     

Preparation and investigation of the physical and chemical properties of clay-based polyacrylamide/Cr (III) hydrogels as a water shut-off agent in oil reservoirs

The effects of clay (montmorillonite and kaolinite) in the hydrogels were investigated on various properties such as syneresis and strength of thermal and salinity situations in one of the southern Iranian oil reservoirs. The X-ray diffraction (XRD) patterns exhibited a significant increase in interplanar spacing between the montmorillonite clay layers, varying from the initial value of 12.43 °A to 19.45 °A, which evidences the intercalation formation. It was revealed that even increasing of the interlayer spacing due to kaolinite modification had no effect on the clay compositions. Formation water was used to study the strength of the hydrogel in the presence of ions. The results indicated that 15 wt% increase of kaolinite clay (modified and non-modified) leads to 20% decrease of the hydrogels’ syneresis. The diffusion of polymer chains between the clay layers increased the elastic modulus (G′) of the prepared hydrogels with modified kaolinite and montmorillonite, where the maximum value of G’ was observed in 3 wt% of montmorillonite. Finally, the thermogravimetric analysis (TGA) indicated an increase in the thermal stability of the mentioned hydrogels.     

Chitosan‐modified nanoclay–poly(AMPS) nanocomposite hydrogels with improved gel strength

BACKGROUND: Making (nano)composite structures is one of the efficient approaches for strengthening hydrogels extended in recent years. The present paper deals with the synthesis and properties of novel nanocomposite hydrogels based on 2‐acrylamido‐2‐methylpropane‐1‐sulfonic acid (AMPS). Initially, a bio‐modified clay, chitosan‐intercalated montmorillonite (chitoMMT), was prepared. Then, this was incorporated into the polymerization of AMPS in the presence of a macro‐crosslinker, i.e. poly(ethylene glycol) dimethacrylate, to yield super‐swelling nanocomposite hydrogels. The swelling capacity as well as some structural, rheological and thermomechanical properties of the hydrogels were studied and compared with those of the clay‐free counterpart. RESULTS: ChitoMMT exhibited no toxicity, which was confirmed using cell‐culture testing. A chitoMMT content of ca 6% was found to be the most favourable content of the bio‐modified clay for achieving a product with improved properties (i.e. the highest gel content, the highest gel strength and optimal thermal stability). Based on a dynamic mechanical thermal analysis study, an increased glass transition temperature (98.2 °C) and improved rubbery modulus (up to 238% higher than that of the clay‐free counterpart) were recorded. Thermogravimetric analysis verified that the thermal stability of nanocomposite samples was higher than that of clay‐free samples. CONCLUSION: Owing to the non‐toxicity of the incorporated chitoMMT, the strengthened hydrogels may be considered as potential candidates for bio‐applications. Copyright © 2009 Society of Chemical Industry