PAAm／PEG／PVP半互穿网络水凝胶的制备、表征及茶碱释放研究．

以N,N-亚甲基双丙烯酰胺（N,N-MBA）为交联剂、过硫酸钾（KPS）为引发剂·通过丙烯酰胺（AAm）、聚乙二醇（PEG）和聚乙烯吡咯烷酮（PVP）发生共聚反应制备具有半互穿网络结构的水凝胶PAAm／PEG／PVP。采用红外光谱（FTIR）、热重分析（TG）对水凝胶的结构和热学性质进行了分析,研究了中性条件下水凝胶的溶胀性能,并进一步研究了其负栽茶碱在不同缓冲溶液中的释放行为。     

聚(N-异丙基丙烯酰胺)/海藻酸钠/黏土复合水凝胶的制备及其性能

以无机黏土为交联剂制备了聚（N-异丙基丙烯酰胺）/海藻酸钠/黏土（PINPA/SA/clay）复合水凝胶,通过红外光谱、X射线衍射和SEM对凝胶的结构和形态进行了表征,并研究了凝胶的溶胀动力学和力学性能。结果表明：黏土的结晶结构已被破坏,黏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;随黏土含量的增加,凝胶网络交联密度增加,孔洞的孔径减小,溶胀速度下降。另外,PINPA/SA/clay凝胶显示了良好的力学性能,断裂伸长率超过1000%。     

P（MA—AA）／PEG水凝胶的制备与性能研究

合成了马来酸酐-丙烯酸共聚物,并与长链分子聚乙二醇交联反应制备了马来酸酐-丙烯酸共聚物／聚乙二醇水凝胶。通过红外光谱对聚合物、水凝胶结构进行了表征,测试了不同pH值下水凝胶的溶胀度以及水凝胶在酸碱条件发生变化时的溶胀速率。研究结果表明,马来酸酐-丙烯酸共聚物／聚乙二醇水凝胶具有较强的吸水溶胀能力,并且对pH值极为敏感：交联剂含量7％的凝胶在pH=10时SR=62657％、pH=2时SR=825％,酸碱条件下具有近百倍的溶胀度变化;并且在pH发生变化时P（MA-AA）／PEG凝胶具有快速的响应速率：由pH=2溶液中转移至pH=10溶液中20min即可溶胀完全,而由pH=10溶液中转移至pH=2溶液中10min即可完全收缩。     

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%。     

丙烯酰胺/丙烯酸水凝胶的pH敏感性研究

测定并研究了丙烯酰胺／丙烯酸凝胶的pH敏感性，及各因素对其性能的影响，实验表明：当丙烯酰胺／丙烯酸比在2：3附近时，形成的凝胶溶胀比最大；随着交联剂含量的增加，会使凝胶的溶胀比显著减小；引发剂含量适当时，可使凝胶溶胀比达到最大。并且从离子强度、相互反应方面对这种变化进行了解释。     

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。     

聚N-丙烯酰基甘氨酸水凝胶的合成及溶胀性能

以N-丙烯酰基甘氨酸（Acgly）为单体、过硫酸铵（APS）为引发剂、亚甲基双丙烯酰胺（MBA）为交联剂,通过溶液自由基聚合得到含有不同交联剂用量的水凝胶,并进行红外光谱表征．实验中对合成的水凝胶在不同pH条件下的平衡溶胀比和溶胀收缩可逆性进行测试．结果表明：随着交联剂质量分数从0.5％增大至7％,水凝胶外观由无色透明变为白色不透明,同时水凝胶由软变硬,弹性变小,硬度增加;在2．8〈pH〈3．8范围内水凝胶的平衡溶胀比随溶液的pH增大迅速增大,水凝胶表现出较好的pH敏感性;在pH=1．0和pH=6．8条件下的水凝胶具有很好的收缩溶胀可逆性．     

NVP接枝壳聚糖水凝胶的合成与溶胀性能

合成了N-乙烯基吡咯烷酮（NVP）接枝壳聚糖（CHI）水凝胶,讨论了NVP/CHI、引发剂、交联剂、聚合温度、乙酸浓度等因素对接枝率及凝胶溶胀性能的影响,NVP∶CHI为6时,接枝率达到300%以上. 溶胀温度、pH值、盐浓度等对凝胶溶胀性能的影响实验表明,凝胶表现出温度敏感性,在40 ℃出现最大平衡溶胀率,并观察到一级相转变;在中性或弱酸性介质中溶胀性能较好;与PVP凝胶相比,NVP接枝CHI凝胶表现出反聚电解质效应. 溶胀动力学研究表明,在溶胀前期,CHI含量较高时,凝胶趋向于非Fick溶胀,说明除了溶剂扩散外,凝胶网络链段弛豫、水分子与凝胶网络间及凝胶高分子链段间相互作用对凝胶溶胀性能的影响至关重要;CHI含量较高时则趋向于Fick溶胀.     

苯乙烯乳液共聚聚丙烯酸复合凝胶制备及溶胀性能

以丙烯酸(AA)为亲水单体、苯乙烯、二乙烯苯为疏水单体,OP-10为乳化剂,在水中进行自由基共聚得到改性凝胶。测定了不同试剂原料配比下的复合结构凝胶的平衡溶胀率、溶胀速率,发现复合结构凝胶(MCG)平衡溶胀率随疏水单体用量增加和乳化剂用量减小而增加,溶胀速率随疏水单体用量增加先增加后降低,随乳化剂用量增加而加快。复合结构凝胶具有弹性体特征,避免了小分子交联剂交联的常规凝胶的脆性。     

pH响应PAAm-g-PEG/PVP半互穿网络水凝胶的制备以及溶胀动力学

采用硝酸铈胺-聚乙二醇为氧化-还原引发体系,N,N-亚甲基双丙烯酰(N,N-MBA)为交联剂,通过简单的自由基聚合法,设计合成了一种聚(丙烯酰胺-g-聚乙二醇)/聚乙烯吡咯烷酮PAAm-g-PEG/PVP接枝交联结构的半互穿网络水凝胶。研究了它们在不同pH值缓冲溶液中的溶胀与扩散行为以及溶胀动力学;并采用红外光谱和热分析系统对其结构和热性能进行了分析测量。实验结果表明:水凝胶的溶胀行为和扩散模式取决于溶液的pH值。随着缓冲溶液pH值增加,平衡溶胀率减小;在不同的缓冲溶液中理论最大吸水量S∞与实验值基本相一致。水凝胶的溶胀行为可以通过选择加入不同分子量大小的PEG来调节和控制。     

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 %。     

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.     

Controlled mechanical and swelling properties of poly(vinyl alcohol)/sodium alginate blend hydrogels prepared by freeze–thaw followed by Ca2+ crosslinking

Poly(vinyl alcohol) (PVA)/sodium alginate (SA) blend hydrogels have immense potential for use as functional biomaterials. Understanding of influences of processing parameters and compositions on mechanical and swelling properties of PVA/SA blend hydrogels is very important. In this work, PVA/SA blend hydrogels with different SA contents were prepared by applying freeze–thaw method first to induce physical crosslinking of PVA chains and then followed by Ca²⁺ crosslinking SA chains to form interpenetrating networks of PVA and SA. The effects of number of freeze–thaw cycles, SA content and Ca²⁺ concentration on mechanical properties, swelling kinetics, and pH‐sensitivity of the blend hydrogels were investigated. The results showed that the blend hydrogels have porous sponge structure. Gel fraction, which is related to crosslink density of the blend hydrogels, increased with the increase of freeze–thaw cycles and strongly depended on SA content. The SA content exerts a significant effect on mechanical properties, swelling kinetics, and pH‐sensitivity of the blend hydrogels. The number of freeze–thaw cycles has marked impact on mechanical properties, but no obvious effect on the pH‐sensitivity of the PVA/SA blend hydrogels. Concentration of CaCl₂ aqueous solution also influences mechanical properties and pH‐sensitivity of the blend hydrogel. By altering composition and processing parameters such as freeze–thaw cycles and concentration of CaCl₂ aqueous solution, the mechanical properties and pH‐sensitivity of PVA/SA blend hydrogels can be tightly controlled. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Poly(N‐isopropylacrylamide‐co‐sodium acrylate) hydrogels: Interactions with surfactants

Poly(N‐isopropylacrylamide‐co‐sodium acrylate) [poly(NIPAM‐co‐SA)] hydrogels were modified with three different kind of surfactants (cationic, anionic, and nonionic) to study the effect on the swelling properties. The structural variation of the surfactant‐modified hydrogels was investigated in detail. The interaction between the surfactants and the hydrogel varies and strictly depends on the surfactant type. The variation in thermal stability of the modified surfactant hydrogels was investigated and compared with unmodified hydrogel. Further, the hydrogel swelling/diffusion kinetic parameters were investigated and diffusion of water into hydrogel was found to be of the non‐Fickian transport mechanism. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3423–3430, 2007     

Preparation and Characterization of Porous Poly (N-isopropylacrylamide) /Clay Nanocomposite Hydrogels

Summary  A novel porous PNIPA/Clay nanocomposite hydrogel (NC hydrogel) was prepared by in situ free-radical polymerization using inorganic clay as a crosslinker and calcium carbonate (CaCO₃) particle as a pore-forming agent and subsequent extraction of CaCO₃ with acid. The structure and morphology of the hydrogels were characterized by means of FTIR, TEM and SEM. The temperature responsive behaviors, the deswelling behaviors and the mechanical properties of the NC hydrogels were investigated in detail. The results showed that the swelling ratios below VPTT and the deswelling rates of the NC hydrogels were significantly improved as compared with the hydrogels without introduction of CaCO₃. Moreover, the NC hydrogels thus prepared also exhibited good mechanical properties.     

A promising porous polymer-nanoclay hydrogel nanocomposite as water reservoir material: synthesis and kinetic study

A porous hydrogel nanocopmposite based on biodegradable salep and montmorillonite (MMT) was synthesized by in-situ free radical graft polymerization of salep chains with acrylic acid (AA) monomers. The chemical structure and morphological properties of the prepared hydrogels was evaluated by FTIR spectroscopy, X-ray diffraction and SEM techniques. The effect of reaction variables such as crosslinker, initiator, monomer and clay contents on equilibrium water absorption capacity and swelling kinetic of hydrogel were investigated and optimized. Swelling behavior of the hydrogels in various pH and saline solutions was also studied. Incorporation of MMT into hydrogel matrix caused the formation of porous hydrogel network. These porous structures resulted in higher water uptake capacity and swelling rate in hydrogel nanocomposite in comparison to neat hydrogel sample. Moreover, hydrogel nanocomposite sample exhibited proper salt and pH-sensitive behavior. High swelling capacity and rate, porosity, salt and pH sensitivity make hydrogel nanocomposite a profitable candidate in agricultural and horticultural applications, such as water reservoir system.     

Antipolyelectrolyte superabsorbing nanocomposites: Synthesis and properties

Novel polyampholytic superabsorbing nanocomposites based on the zwitterionic sulfobetaine monomer [3‐(methacrylamido)propyl)]dimethyl(3‐sulfopropyl)ammonium hydroxide were synthesized through in situ polymerization in aqueous solution with different contents of an organo‐modified clay (OMMT, Cloisite 30B). Structural and thermomechanical properties of hydrogels were characterized by FT‐IR, XRD, and DMTA, respectively. Swollen gel strength of hydrogels was determined by a rheological method. Storage modulus of the hydrogels was considerably improved in comparison with its the clay‐free counterpart. The nanocomposite hydrogel containing 15% OMMT possessed the highest gel strength. The glass transition temperature was increased from 58.4 to 67.0°C for the clay‐free and nanocomposite hydrogel containing 8% OMMT, respectively. The swelling behavior of the hydrogel in various salt solutions was investigated. Antipolyelectrolyte behavior was observed with enhancement of concentration of mono‐ and multivalent salts. Swelling in the various pH media was nearly pH‐independent over a wide range of pH. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of pH‐ and temperature‐responsive semi–interpenetrating polymer network hydrogels based on linear sodium alginate and crosslinked poly(N‐isopropylacrylamide)

In this study, pH‐ and temperature‐responsive hydrogels based on linear sodium alginate (SA) and crosslinked poly(N‐isopropylacrylamide) (PNIPAAm) were prepared by semi‐interpenetrating network (semi‐IPN) technique. The dually responsive hydrogels were characterized by FTIR, DSC, and SEM, and their temperature‐ and pH‐responsive behaviors were investigated by measuring equilibrium swelling ratios and pulsatile swelling experiments. The results showed that these hydrogels underwent volume phase transition at around 33°C irrespective of the pH value of the medium, but their pH sensitivity was evident only below their volume phase transition temperature. Under basic conditions, the swelling ratios of SA/PNIPAAm semi‐IPN hydrogels were greater than that of pure PNIPAAm hydrogel and increased with increasing SA content incorporated into the hydrogels, but the case was inverse under acidic conditions. The pulsatile swelling experiments indicated that the higher the SA content in SA/PNIPAAm semi‐IPN hydrogels, the faster the response rate to both pH and temperature change. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1931–1940, 2005     

Water sorption behavior of CMC/PAM hydrogels prepared by γ-irradiation and release of potassium nitrate as agrochemical

Novel types of highly swelling CMC/PAM hydrogels have been prepared by grafting cross-linked polyacrylamide (PAM) chains onto carboxymethylcellulose (CMC) via a free radical polymerization method using γ-irradiation. The prepared CMC/PAM hydrogels were characterized by FT-IR spectral analysis. The AM content and irradiation dose had a direct effect on gel content of CMC/PAM hydrogels and inverse effect on their swelling ratio. The hydrogels showed enormous swelling in aqueous medium and displayed swelling characteristics which were highly dependent on the chemical composition of the hydrogel, pH and ionic strength of the medium in which the hydrogel was immersed. The results were supported by morphological properties of CMC/PAM hydrogels by using SEM. The kinetics of water uptake and the water transport mechanism were studied as a function of the CMC/AM ratio into the prepared hydrogel. The release rate of potassium nitrate entrapped within the CMC/PAM matrix increased by enhancing its loading %, and decreased with lowering AM content and irradiation dose.