Novel Cationic Poly[AAm/NVP/DAPB] Hydrogels for Removal of Some Textile Anionic Dyes from Aqueous Solution

Novel cationic poly [AAm/NVP/DAPB] hydrogels (YH₁ – YH₅) were synthesized by free radical solution polymerization of AAm, NVP and DAPB by increasing the concentration of DAPB in the feed. According to swelling experiments, hydrogel YH₅ with higher DAPB content gave relative higher swelling percentage compared to other hydrogels. The hydrogel YH₅ was characterized by FTIR, TGA and SEM analysis. The anionic dye solution such as Orange-II, Reactive Golden Yellow and Acid Yellow were used as an adsorption medium to investigate the usability of the hydrogel for the removal of anionic dyes. The effect of pH of the adsorption medium, initial concentration of the dye, adsorbent dose, %swelling and contact time was also investigated. Furthermore, the Langmuir and Freundlich adsorption isotherms were applied and they showed a good fit to the experimental data. From the results, the uptake of dyes within the hydrogel increased in the following order: Reactive Golden Yellow>Orange-II>Acid Yellow.     

Preparation of a novel pH-responsive silver nanoparticle/poly(HEMA-PEGMA-MAA) composite hydrogel

In this paper, series of novel pH-responsive silver (Ag) nanoparticle/poly(2-hydroxyethyl methacrylate (HEMA)-poly(ethylene glycol) methyl ether methacrylate (PEGMA)-methacrylic acid (MAA)) composite hydrogel were successfully prepared by in situ reducing Ag⁺ ions anchored in the hydrogel by the deprotonized carboxyl acid groups. X-ray diffraction (XRD), UV-vis spectrophotometry, transmission electron microscopy (TEM) and electric conductivity tests were used to characterize the composite system. It was found that the size and morphology of the reduced Ag nanoparticles in the composite hydrogels could be changed by loading the Ag⁺ ions at various swelling ratios of hydrogel. Moreover, compared to the pure poly(HEMA-PEGMA-MAA) hydrogel, not only did the Ag nanoparticle/poly(HEMA-PEGMA-MAA) composite hydrogels exhibit much higher swelling ratio and faster deswelling rate, but also higher pH switchable electrical properties upon controlling the interparticle distance under pH stimulus. The pH responsive nanocomposite hydrogel reported here might be a potentially smart material in the range of applications including electronics, biosensors and drug-delivery devices.     

大孔PAMPS/PVA半互穿网络型水凝胶的制备及其性能研究

以PEG6000为成孔剂, 合成了大孔聚(2-丙烯酰胺-2-甲基丙磺酸)/聚乙烯醇半互穿网络型(s-IPN)水凝胶. 红外分析表明, PVA与PAMPS之间形成了较强的氢键, 使得PVA分子上的C—O伸缩振动吸收峰移向了低波数处. X射线衍射分析发现, 当PVA用量较高时, 由于部分的PVA结晶, 使得凝胶的半互穿网络结构不均匀. 电镜分析结果表明, 没有使用成孔剂的凝胶表面成褶皱形, 不存在任何孔洞结构; 而以PEG6000为成孔剂的凝胶表面存在相互贯穿的大孔结构. 研究了该水凝胶的溶胀性能, 结果表明, 该水凝胶的平衡溶胀度在116至320之间; 而成孔剂PEG6000的加入能较大幅度提高凝胶的溶胀速率, 凝胶在240 min之内就能达到溶胀平衡. 对凝胶抗压缩性能的研究表明, 当PVA用量为9.1% (w)时, 凝胶的抗压缩强度最大, 可达12.0 MPa; 而成孔剂的加入会在一定程度削弱凝胶的抗压缩强度. 该凝胶具有较好的电场敏感性, 研究发现, 将吸去离子水达到溶胀平衡的凝胶放入施加有电场的0.2 mol•L－1 NaCl溶液中时, 凝胶迅速偏向阳极. 而PVA和成孔剂PGE6000的用量均对凝胶的偏转速度以及最大偏转角存在较大的影响.     

羧甲基纤维素钠/聚(N-异丙基丙烯酰胺)纳米复合水凝胶的制备及结构性能表征

以无机粘土为交联剂制备了具有温度、pH双重敏感特性的羧甲基纤维素钠/聚(N-异丙基丙烯酰胺)/粘土半互穿网络纳米复合水凝胶(CMC/PNIPA/Clay semi-IPN),并通过红外和透射电镜对其结构和形态进行了表征。在酸性(pH=1.2)和20℃条件下,分别研究了温度和不同pH缓冲液对该凝胶溶胀度的影响,测定了复合水凝胶的力学性能。结果表明:水凝胶中的粘土被剥离成单片层,且均匀分散在凝胶网络中,起交联剂的作用,而CMC以线性大分子的形态存在;CMC/PNIPA/Clay具有良好的温度、pH双重敏感特性;凝胶的断裂伸长率>1 000%。     

Macroporous Poly(Acrylamide) Hydrogels: Swelling and Shrinking Behaviors

Macroporous poly(acrylamide) hydrogels have been synthesized by using poly(ethylene glycol) (PEG) with three different molecular weights as the pore‐forming agent. Scanning electron microscope graphs reveal that the macroporous network structure of the hydrogels can be adjusted by applying different molecular weights of PEG during the polymerization reaction. The swelling ratios of the PEG‐modified hydrogels were much higher than those for the same type of hydrogel prepared via conventional method. However, the swelling/deswelling ratios of the PEG‐modified hydrogels were affected slightly by the change in the amount of the PEG. Scanning electron microscopy experiments, together with swelling ratio studies, reveal that the PEG‐modified hydrogels are characterized by an open structure with more pores and higher swelling ratio, but lower mechanical strength, compared the conventional hydrogel. PAAm has potential applications in controlled release of macromolecular active agents.     

Preparation and characterization of sodium carboxymethylcellulose/poly(N-isopropylacrylamide)/clay semi-IPN nanocomposite hydrogels

A new kind of pH-/temperature-responsive semi-interpenetrating polymer network hydrogels based on linear sodium carboxymethylcellulose (CMC) and poly(N-isopropylacrylamide) (PNIPA) cross-linked by inorganic clay (CMC/PNIPA/Clay hydrogel) was prepared. The temperature- and pH-responsive behaviors, the mechanical properties of these hydrogels were investigated. The CMC/PNIPA/Clay hydrogels exhibited a volume phase transition temperature around 32 °C with no significant deviation from the conventional PNIPA hydrogels. The swelling ratio of the CMC/PNIPA/Clay hydrogels gradually decreased with increasing the contents of clay. The influence of pH value on swelling behaviors showed that there is a maximum swelling ratio at pH 5.9. Moreover, the CMC/PNIPA/Clay hydrogels exhibited excellent mechanical properties with high tensile stress and elongation at break in excess of 1200%.     

快速响应的温敏性聚(N-异丙基丙烯酰胺)水凝胶的合成及表征

快速响应的温敏性聚(N-异丙基丙烯酰胺)水凝胶的合成及表征;N-异丙基丙烯酰胺;水凝胶;温敏性;快速响应     

Synthesis of poly(ethylene glycol)‐based hydrogels and their swelling/shrinking response to molecular recognition

To synthesize the novel molecular‐ and pH‐stimulus‐responsive hydrogel, we prepared poly(ethylene glycol)‐based hydrogel containing ionic groups. We evaluated the fundamental swelling/shrinking properties of the hydrogels synthesized by various conditions. Decreasing the molecular weight of a crosslinker provided the increasing of the equilibrium swelling ratio. Also, the equilibrium swelling ratio was changed by the introduction of functional ionic monomers and its compositions. Furthermore, the swelling/shrinking behaviors of the hydrogels were affected by the environmental condition of aqueous solution, in fact the hydrogels were considerably shrunk (to one‐fifth volume) using a di‐ionic solute in the aqueous solution through the ionic interactions between the hydrogel and the solutes. Additionally, the specific shrinking to diamine compounds was also observed in response to pH change. These results clearly show the swelling/shrinking responsibility of the hydrogels toward the molecular recognitions and its pH conditions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3153–3158     

Synthesis of the Functional Hydrogels: Poly(N-isopropylacrylamide) Threaded onto the PEG Backbones Via RAFT

Functional poly(N-isopropylacrylamide) (PNIPAM) hydrogels were prepared by reversible addition fragmentation chain transfer (RAFT) polymerization of NIPAM in the presence of four-arm poly(ethylene glycol) (4A-PEG) as backbone and 4-cyanopentanoic acid dithiobenzoate functional α -cyclodextrin threaded onto the PEG as chain transfer reagent (CTA).The structure of the hydrogels was characterized in detail with FTIR techniques. The analytical results demonstrated that α -cyclodextrin remains in as-obtained hydrogels. The swelling behavior was investigated and the functional hydrogels (functional gels) showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional hydrogel (CG). It could be attributed to the presence of dangling chains. The hydrogel exhibited rapid swelling and deswelling kinetics. In principle, the hydrogel might find a number of applications including an on-off system and drug delivery systems.     

Rapid swelling and deswelling in cryogels of crosslinked poly(N-isopropylacrylamide-co-acrylic acid)

Thermally sensitive hydrogels of poly[N-isopropylacrylamide (NIPA)-co-acrylic acid (AA)] hydrogels with N,N-methylene bisacrylamide (BIS) as crosslinker have been synthesized via a two-step procedure in which, the initial polymerisation is conducted for various times at 18 °C, this step being followed by polymerisation for one fixed time at −22 °C. The gravimetrically determined rates of swelling/deswelling for these materials termed “cryogels” prepared by this two-step polymerisation are much higher than those for the same type of hydrogel prepared via conventional methods (30 °C for 24 h). For example the time for the former xerogel to take up 70% of its final water content at 25 °C is just 18 min, compared with a time 300 min for the latter to attain the same uptake of water. During deswelling (shrinking) at 50 °C, which is above the lower critical temperature, the hydrogel loses 60 and 90 wt% water in 1 and 10 min respectively, compared to a timescale for the corresponding crosslinked copolymers prepared by conventional methods of about 100 min for 50 wt% water loss. A third type of hydrogel was made by a cold treatment (CT), for which the hydrogel prepared by conventional polymerization was stored in the frozen state. The swelling rate of these CT xerogels was the same as that for xerogels prepared by conventional polymerization, but the deswelling rate of the former was higher than that of the latter; for example, during deswelling, a loss of 90% water is attained within a few minutes.Scanning electron microscopy, digital photographs and flotation experiments together with swelling ratio studies reveal that the polymeric network of cryogel produced by the two-step polymerization method is characterized by an open structure with more pores and higher swelling ratio but lower mechanical strength compared to the conventional hydrogels. Such rapid response hydrogels have potential applications in separation and drug release technologies for example.     

交联聚(N-异丙基丙烯酰胺)/(海藻酸钠/聚(N-异丙基丙烯酰胺))半互穿网络水凝胶的制备及其溶胀性能

将线性聚(N-异丙基丙烯酰胺)(PNIPAAm)和海藻酸钠(SA)分子同时引入到PNIPAAm凝胶中,制备了交联聚(N-异丙基丙烯酰胺)/(海藻酸钠/聚(N-异丙基丙烯酰胺))半互穿网络(Cr-PNIPAAm/(SA/PNIPAAm)semi-IPN)水凝胶。在弱碱性条件下(pH=7.4),改变SA与线性PNIPAAm的质量比对Cr-PNIPAAm/(SA/PNIPAAm)semi-IPN水凝胶的溶胀度没有太大的影响。在酸性条件下(pH=1.0),其溶胀度随着SA与线性PNIPAAm质量比的减小而增大。由于亲水性SA与线性PNIPAAm的协同作用,Cr-PNIPAAm/(SA/PNIPAAm)semi-IPN水凝胶的消溶胀速率得到很大提高。     

丝素蛋白-聚氨酯复合水凝胶的制备及性能研究

以聚乙二醇(PEG)、聚氧化丙烯二醇(PPG)、异弗尔酮二异氰酸酯(IPDI)为主要原料制备聚氨酯预聚体(PU),与丝素蛋白水溶液(SF)交联制得丝素蛋白-聚氨酯(SF-PU)复合水凝胶.分别利用ATR、SEM对水凝胶组成、结构及微观形貌进行表征;DSC、吸水溶胀测试探讨了丝素蛋白与聚氨酯的质量比(SF/PU)以及聚氨酯中不同软段质量比(PEG/PPG)对SF-PU水凝胶热性能、溶胀性能的影响.结果表明,SF-PU水凝胶具有多孔结构;样品中不同的SF/PU、PEG/PPG均对材料的玻璃化转变温度、结晶度及溶胀性能产生影响,且当水凝胶组分为SF/PU=1/25、PEG/PPG=2/1时,平衡溶胀比(ESR)可达到440%;水凝胶在溶胀初始阶段符合菲克扩散模型,整个溶胀过程遵循溶胀动力学2级方程.     

聚N-异丙基丙烯酰胺/纳米SiO_2复合水凝胶的合成及溶胀性能

通过纳米SiO2的表面功能化,在其表面引入乙烯基功能基团,在H2OTHF的混合溶剂中,超声分散后,交联剂N,N′亚甲基双丙烯酰胺存在时,于25℃下使其与N异丙基丙烯酰胺共聚,制得聚N异丙基丙烯酰胺纳米SiO2复合水凝胶,并用FTIR和SEM对产物进行了表征.研究了凝胶的溶胀动力学,消溶胀动力学和温度敏感性.实验结果表明,纳米SiO2的引入,改善了聚N异丙基丙烯酰胺水凝胶在低温时的溶胀性能和在高温时对水的释放性能,并讨论了引起这些性能改变的原因.     

Rapid swelling and deswelling in cryogels of crosslinked poly(N-isopropylacrylamide-co-acrylic)

Thermally sensitive hydrogels of poly[N-isopropylacrylamide (NIPA)-co-acrylic(AA)] hydrogels with N,N-methylene bisacrylamide (BIS) as crosslinker have been synthesised via a two-step procedure in which, the initial polymerisation is conducted for various times at 18 °C, this step being followed by polymerisation for one fixed time at −22 °C. The gravimetrically determined rates of swelling/deswelling for these materials termed “cryogels” prepared by this two-step polymerisation are much higher than those for the same type of hydrogel prepared via conventional methods (30 °C for 24 h). For example the time for the former xerogel to take up 70% of its final water content at 25 °C is just 18 min, compared with a time 300 min for the latter to attain the same uptake of water. During deswelling (shrinking) at 50 °C, which is above the lower critical temperature, the hydrogel loses 60 and 90 wt.% water in 1 and 10 min respectively, compared to a timescale for the corresponding crosslinked copolymers prepared by conventional methods of about 100 min for 50 wt.% water loss. A third type of hydrogel was made by a cold treatment (CT), for which the hydrogel prepared by conventional polymerisation was stored in the frozen state. The swelling rate of these CT xerogels was the same as that for xerogels prepared by conventional polymerisation, but the deswelling rate of the former was higher than that of the latter; for example, during deswelling, a loss of 90% water is attained within a few minutes.Scanning electron microscopy, digital photographs and flotation experiments together with swelling ratio studies reveal that the polymeric network of cryogel produced by the two-step polymerisation method is characterised by an open structure with more pores and higher swelling ratio but lower mechanical strength compared to the conventional hydrogels. The polymerisation was taking place on moderate freezing condition and the hydrogel was stored in a frozen state and subsequent thawing of polymer to be very useful the acceleration the response rate of this kind hydrogels. Such rapid response hydrogels have potential applications in separation and drug release technologies for example.     

pH敏感的聚(L-谷氨酸)-交联聚丙烯酸水凝胶的合成与性能研究

通过在聚L-谷氨酸侧链部分接枝甲基丙烯酸2-羟乙酯得到含有双键的聚(L-谷氨酸),将其与丙烯酸共聚得到由聚(L-谷氨酸)侧链接枝并交联聚丙烯酸的pH敏感水凝胶.研究水凝胶在不同pH的缓冲溶液中的溶胀性、溶胀动力学,并通过SEM观察水凝胶的微观结构.结果表明,水凝胶在低pH环境下的溶胀率明显低于高pH环境中的溶胀率,不同...     

Microstructured polyacrylamide hydrogels made with hydrophobic nanoparticles

Poly(methyl methacrylate) nanosize particles, made by microemulsion polymerization, were dispersed in an acrylamide aqueous solution, which was polymerized in the presence of a cross-linking agent to yield microstructured hydrogels. The kinetics of swelling and the mechanical properties of these hydrogels were investigated as a function of concentration of particles. The microstructured hydrogels exhibit higher equilibrium swelling and larger Young modulus than conventional (that is, without particles) polyacrylamide hydrogel. The morphology of the microstructured hydrogels was examined by transmission electron microscopy.     

Manufacturing of pH sensitive PVA/PVP/MWCNT and PVA/PEG/MWCNT nanocomposites: an approach for significant drug release

The purpose of this paper is studying the effect of incorporation of Multiwall Carbon Nanotubes (MWCNT) into two different nanocomposites in poly vinyl alcohol (PVA)/polyvinylpyrrolidone (PVP), and PVA/Polyethylene glycol (PEG). MWCNT were synthesized by chemical vapor deposition (CVD) method using acetylene and Fe/Co/Al₂O₃ as carbon precursor and catalyst, respectively. Nitric acid and sulfuric acid were used for purification and functionalization of MWCNT. Afterward, highly pure and functionalized MWCNT (0, 0.02, and 0.05% w/w) were incorporated in PVA/PVP and PVA/PEG to synthesize PVA/PVP/MWCNT and PVA/PEG/MWCNT nanocomposites hydrogel membranes that cross-linked by freezing–thawing. PEG and PVP were selected in these nanocomposites as dispersion matrix for MWCNT as well as for increasing the elasticity of the nanocomposites membranes. The morphology of the hydrogels was characterized by SEM, FTIR, XRD, TGA, and the mechanical properties of the hydrogel membranes were investigated. The swelling behavior in different pH-buffer solutions was studied as well as studying weight loss percentage and swelling kinetic. The drug releasing process of the hydrogel membranes was investigated using salicylic acid as a model drug. It was found that MWCNT are dispersed well into the polymers and crystallinity, mechanical properties and thermal stability of the hydrogels contain MWCNT are better than that without MWCNT. Maximum degree of swelling was observed at pH 7 and swelling degree increases with increasing the ratio of MWCNT in the hydrogels from 0.02 to 0.05%. All hydrogel membranes followed non-Fickian mechanism and drug releasing were controlled by varying the pH and amount of MWCNT.     

Photo cross-linked biodegradable hydrogels for enhanced vancomycin loading and sustained release

A series of biodegradable hydrogels based on dextran and poly（L-glutamic acid） were fabricated for effective vancomycin loading and release. The preparation of hydrogels was simply achieved by photo cross-linking of methacrylated dextran and poly（L-glutamic acid）-g-hydroxyethyl methacrylate （PGH） in the presence of photoinitiator 12959. The structures of hydrogels were characterized by FTIR and SEM. The swelling and enzymatic degradation behaviors of hydrogels were examined to be dependent on the poly（L-glutamic acid） content in the hydrogels. The higher content of poly（L-glutamic acid） in the gel, the higher swelling ratio and quicker degradation were observed. More interestingly, the hydrogel with higher PGH ratio showed higher vancomycin （VCM） loading content, which might be due to the electrostatic interaction between carboxylate groups in hydrogel and ammonium group of VCM. In vitro drug release from the VCM-loaded hydrogels in aqueous solution exhibited sustained release of VCM up to 72 h, while the in vitro antibacterial test based on the VCM-loaded hydrogel showed an efficient Methicillin-Resistant S. aureus （MRSA） inhibition extending out to 7 days. These results demonstrated that the biodegradable hydrogels which formed by in situ photo-cross linking would be promising as scaffolds or coatings for local antibacterial drug release in tissue engineering.     

Swelling behaviors of thermoresponsive hydrogels cross-linked with acryloyloxyethylaminopolysuccinimide

Based on a biodegradable cross-linker, acryloyloxyethylaminopolysuccinimide (AEA-PSI), a series of looser cross-linked poly(N-isopropylacrylamide-co-acrylic acid) [P(NIPAAm-co-AAc)] hydrogels were prepared, and their water content, swelling/deswelling kinetics, and the morphology of the gels were investigated. The swelling behaviors of AEA-PSI-cross-linked P(NIPAAm/AAc) hydrogels were investigated in Dulbecco’s phosphate-buffered saline (pH = 7.4), in the distilled water, and in the simulated gastric fluids (pH = 1.2), respectively. The water contents of the hydrogels were controlled by the monomer molar ratio of NIPAAm/AAc, swelling media, and the temperature. In the swelling kinetics, all the dried hydrogels exhibited fast swelling behavior, and the swelling ratios were influenced significantly by the amounts of AEA-PSI and AAc content. The deswelling kinetics of the hydrogel were independent of the content of AAc and cross-linker. Lastly, the morphology of the hydrogels was estimated by the field scan electron microscopy.     

Amphoteric surface hydrogels derived from hydrogen-bonded multilayers: reversible loading of dyes and macromolecules

We used hydrogen-bonded multilayers of poly(N-vinylpyrrolidone) (PVPON) and poly(methacrylic acid) (PMAA) as precursors for producing surface-bound hydrogels and studied their pH-dependent swelling and protein uptake behavior using in situ attenuated total reflection Fourier transform infrared spectroscopy and in situ ellipsometry. The hydrogels were produced by selective chemical cross-linking between PMAA units using carbodiimide chemistry and ethylenediamine (EDA) as a cross-linking reagent, followed by complete removal of PVPON from the film obtained by exposing the film to pH 7.5. As shown by in situ ellipsometry, hydrogels exhibit distinctive polyampholytic swelling as a function of pH, with minimum swelling at pH 4.2-5.7, and increased film thickness at both lower and higher pH values. Film swelling at lower pH values occurs as a result of the presence of amino groups within the hydrogels, which originate from the one-end attachment of the EDA cross-linker to PMAA chains. The pH-switching of hydrogel swelling was fast and reversible. The degree of hydrogel swelling could be also controlled by varying the time allowed for cross-linking. The produced hydrogels were able to absorb large amounts of dyes and proteins of opposite charge reversibly, in response to pH variations. Finally, we demonstrate that proteins included within the hydrogel can easily be replaced with linear polycations. These surface hydrogels hold promise for bioseparation and controlled delivery applications.