聚丙烯酸钠/聚乙烯醇复合水凝胶的制备及其电响应行为

以过硫酸钾为引发剂,N, N′-二甲基双丙烯酰胺为交联剂结合冷冻-解冻交联,制备了一系列不同配比的聚丙烯酸钠(PAAS)/聚乙烯醇(PVA)互穿网络水凝胶,并用傅里叶红外光谱仪(FTIR)、场发射扫描电子显微镜(SEM)、热失重分析仪(TG)、万能试验机等对其进行表征。结果表明,PVA均匀分散于互穿网络水凝胶中,PVA的加入可以提高PAAS水凝胶的热性能;使PAAS水凝胶的溶胀速率和最大溶胀度减小,在PVA含量达到14%(质量分数,下同)时最低,随后又提高;PVA的加入可以显著提高其力学性能,断裂伸长率和拉伸强度均随PVA含量的增加而增大;PVA的加入提高了互穿网络的电响应灵敏度,且其最佳含量为21%。     

PAAS/PVA/Zn0.2Fe2.8O4磁性复合水凝胶的合成及其性能研究

以化学共沉淀法制备了在水中分散性良好的柠檬酸包覆的掺锌纳米四氧化三铁（Zn_0.2Fe_2.8O₄,ZFO）粒子,并用X射线衍射仪、透射电子显微镜及综合物理特性测试仪进行测试。结果表明,该纳米粒子粒径为3~8 nm,粒径较为均一且饱和磁化强度可达60 emu/g,再通过在水相中引发丙烯酸钠聚合交联并结合冷冻解冻交联制得聚乙烯醇/聚丙烯酸钠/ZFO（PVA/PAAS/ZFO）互穿网络水凝胶;纳米ZFO粒子的引入可同时使水凝胶的拉伸强度提高约1.5倍; ZFO粒子的加入对水凝胶的热稳定性有一定的提高;纳米ZFO粒子的引入可加快水凝胶的电响应的速率和程度。     

纳米银对复合水凝胶性质影响的研究

超声波作用于含有单体AMPS、MMA和交联剂MBA的Ag NO3水溶液,使Ag+还原为纳米级的银粒子,与此同时单体和交联剂形成共聚物,从而在无引发剂和还原剂的条件下制备出纳米银/P(AMPS-MMA)复合水凝胶。TEM表明,制备的纳米银粒径在10~20nm,粒径分布较窄,且均匀地分散在水凝胶聚合物里;通过研究纳米银/P(AMPS-MMA)复合水凝胶和P(AMPS-MMA)水凝胶的溶胀率、溶胀动力学、退溶胀动力学和温敏性质等表明,纳米银增强了复合水凝胶的吸水性能和提高了复合水凝胶的温敏性。     

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.     

温度及pH敏感性聚乙烯醇/羧甲基壳聚糖水凝胶的制备与性能研究

以聚乙烯醇(PVA)和羧甲基壳聚糖(CMCh)为原料,采用60Co-γ射线辐照交联制备聚乙烯醇/羧甲基壳聚糖(PVA/CMCh)水凝胶;研究了PVA与CMCh的配比、温度、pH及离子强度等对PVA/CMCh水凝胶溶胀率的影响。结果表明适当配比的PVA/CMCh水凝胶具有一定的温度、pH及离子敏感性。该水凝胶在5~20°C时具有较高的溶胀率,温度在20°C以上溶胀率较低,并且有一定的可逆性;水凝胶在pH较低(pH<4.0)和较高(pH>6.0)时溶胀率均较大,而当pH为4.0~6.0时溶胀率较小,显示出一定的pH敏感性。     

互穿网络水凝胶的制备及其性能

以丙烯酸(AA)、N-乙烯基吡咯烷酮(NVP)和N-异丙基丙烯酰胺为主要原料(NIPAM),以N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,过硫酸钾为引发剂,采用分步法制备互穿网络水凝胶。研究了水凝胶的溶胀动力学,探究了在不同温度、p H和盐溶液浓度下水凝胶的溶胀率。结果表明,随着温度的上升,水凝胶的溶胀率呈递减的趋势。溶液的碱性越强,水凝胶吸水性越好,在p H大于8以后,吸水性能基本达到稳定。当水溶液浓度升高时,凝胶的溶胀率呈快速递减的趋势。     

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。     

螺旋纳米炭纤维/海藻酸钠水凝胶制备及性能研究

通过溶液共混法制备海藻酸钠(SA)水凝胶和螺旋纳米炭纤维/海藻酸钠(HCNFs/SA)复合水凝胶,考察SA浓度、CaCl_2浓度和HCNFs浓度对凝胶平衡溶胀度(ESD)的影响,并对水凝胶进行pH值响应性和抗压强度测试。结果表明:SA浓度为1%、CaCl_2浓度为0.03 mol/L时,制备的水凝胶ESD为34.72;HCNFs浓度为0.5 mg/mL时,制备的HCNFs/SA水凝胶抗压强度为7.84 kPa。     

纳米钴复合凝胶的制备及催化降解对硝基苯酚的应用

本文采用自由基聚合法,以水为反应介质,丙烯酸(AA)为单体,N.N’-亚甲基双丙烯酰胺(BIS)为交联剂,过硫酸铵(APS)为引发剂,合成了高溶胀比的聚丙烯酸水凝胶。该凝胶吸附金属Co2+离子后,用硼氢化钠还原剂通过原位还原得到纳米钴复合凝胶。用红外光谱仪(FT-IR)、XRD对所得产品进行表征,证明金属钴以纳米粒子的形态分散在凝胶网络中。将纳米钴复合水凝胶作为催化剂,在水中催化过量硼氢化钠还原对硝基苯酚(4-NP),并在不同条件下研究了催化活性,结果表明,该反应符合一级动力学方程,表观活化能约为21.11 k J·mol-1。单体浓度为15%、交联度为1%时活性较好,增大反应温度和复合凝胶的投入量均可以加快催化反应速率。     

GA-g-PAA/ST复合水凝胶的合成与表征

以阿拉伯胶(GA)、丙烯酸(AA)、海泡石黏土(ST)为原料,采用微波辐射法,通过接枝共聚合成了GA-g-PAA/ST复合水凝胶,利用FTIR、XRD和SEM表征了水凝胶的结构和形貌,用TG分析了水凝胶的热稳定性能,同时探讨了水凝胶在不同价态阳离子盐溶液的溶胀行为和保水性能。结果显示:GA、ST和AA发生了接枝共聚反应,共聚物插层到ST的层间,形成剥离型均匀的三维网络复合高吸水性水凝胶。当盐溶液浓度为20 mmol/L时,水凝胶在NaCl、BaCl_2、AlCl_3溶液中的吸水倍率分别为112、38和29 g/g。表面活性剂溶液浓度为20 mmol/L时,水凝胶在十二烷基硫酸钠(SDS)和十六烷基三甲基溴化铵(CTAB)溶液的吸水倍率分别为135和105 g/g。水凝胶在NaCl和BaCl_2溶液经过3次溶胀-去溶胀循环后,其吸水倍率分别为80和12 g/g,表明水凝胶在NaCl和BaCl_2盐溶液中具有较强的盐响应性能和良好的可逆行为,水凝胶具有较好的热稳定性和保水性能。     

PVA/Fe2O3磁敏感性水凝胶的制备及性能

采用循环冷冻-解冻方法制备了聚乙烯醇(PVA)/Fe2O3磁敏感性水凝胶. 考察了水凝胶的力学性能、溶胀性能和磁敏感性,并用扫描电镜观察了其表面形貌. 结果表明,当Fe2O3含量为1%(w)时,水凝胶的力学性能最好;水凝胶的溶胀度和脱水率随时间增加有相似的变化趋势,都随磁性粒子含量升高而降低;溶胀性能降低其交联程度增加;PVA和Fe2O3相容性较好;水凝胶在3000 Oe的磁场强度下达到饱和,呈现出很强的顺磁性,磁滞损耗较多,表明具有较好的磁敏感性.     

Porous boron nitride nanofibers/PVA hydrogels with improved mechanical property and thermal stability

Polyvinyl alcohol (PVA) hydrogel is a promising material possessing good chemical stability, high water absorption, excellent biocompatibility and biological aging resistant. However, the poor mechanical performance of PVA hydrogel limits its applications. Here we report the utilization of one-dimensional (1D) BN nanofibers (BNNFs) as nanofillers into PVA matrix to prepare a novel kind of BNNFs/PVA composite hydrogel via a cyclic freezing and thawing method. For comparison, the composite hydrogels using spherical BN nanoparticles i.e. BN nanospheres (BNNSs) as fillers were also prepared. The mechanical properties, thermal stabilities and swelling behaviors of the composite hydrogels were investigated in detail. Our study indicates that the mechanical properties of the hydrogels can be improved by adding of BNNFs. After loading of BNNFs into PVA with content of 0.5?wt%, the compressive strength of the composite hydrogel increases by 252% compared with that of pure PVA hydrogel. The tensile performance of BNNFs/PVA composite hydrogels has also been improved. Impressive 87.8% increases in tensile strengths can be obtained with 1?wt% BNNFs added. In addition, with the increase of BNNFs content, the thermal stability and the swelling ratio of hydrogels are increased gradually. The swelling ratio of hydrogel increases by 56.3% with only 1?wt% BNNFs added. In comparison, the improvement effects of the BNNS fillers on the mechanical strengths and swelling ratios are much weaker. The enhanced effects of BNNFs can be ascribed to the strong hydrogen bond interaction between BNNFs and PVA. The high aspect ratios of the nanofibers should also be took into account.     

Preparation of fast pH‐responsive ferric carboxymethylcellulose/poly(vinyl alcohol) double‐network microparticles

BACKGROUND: Carboxymethylcellulose (CMC) and poly(vinyl alcohol) (PVA) are biocompatible, and their complex hydrogel shows pH responsiveness. Thus, they are chosen as starting materials to prepare physically dual‐crosslinked Fe‐CMC/PVA microparticles with improved properties. RESULTS: Fe‐CMC/PVA double‐network microparticles were obtained via a facile process under mild conditions. Sodium carboxymethylcellulose was crosslinked with ferric ions to form particles that contained aqueous PVA solution in an emulsion system. The hydrogel particles were then subjected to a freezing–thawing cycle to achieve further crosslinking; the size of the particles formed was in the range 0.2–1.2 µm. The microparticles were capable of maintaining the stability of proteins such as hemoglobin in an acidic environment and exhibited pH‐responsive release behavior. CONCLUSION: The pH responsivity of the Fe‐CMC/PVA physical double‐network microparticles is fast, which is helpful for effectively protecting a loaded bioactive substance. Thus, they may be potential candidates for pH‐sensitive applications. Copyright © 2008 Society of Chemical Industry     

Preparation and swelling properties of semi‐IPN hydrogels based on chitosan‐g‐poly(acrylic acid) and phosphorylated polyvinyl alcohol

The phosphorylated poly(vinyl alcohol) (P‐PVA) samples with various substitution degrees were prepared through the esterification reaction of PVA and phosphoric acid. By using chitosan (CTS), acrylic acid (AA) and P‐PVA as raw materials, ammonium persulphate (APS) as an initiator and N,N‐methylenebisacrylamide as a crosslinker, the CTS‐g‐PAA/P‐PVA semi‐interpenetrated polymer network (IPN) ssuperabsorbent hydrogel was prepared in aqueous solution by the graft copolymerization of CTS and AA and followed by an interpenetrating and crosslinking of P‐PVA chains. The hydrogel was characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) techniques, and the influence of reaction variables, such as the substitution degree and content of P‐PVA on water absorbency were also investigated. FTIR and DSC results confirmed that PAA had been grafted onto CTS backbone and revealed the existence of phase separation and the formation of semi‐IPN network structure. SEM observations indicate that the incorporation of P‐PVA induced highly porous structure, and P‐PVA was uniformly dispersed in the polymeric network. Swelling results showed that CTS‐g‐PAA/P‐PVA semi‐IPN superabsorbent hydrogel exhibited improved swelling capability (421 g·g^?1 in distilled water and 55 g·g^?1 in 0.9 wt % NaCl solution) and swelling rate compared with CTS‐g‐PAA/PVA hydrogel (301 g·g^?1 in distilled water and 47 g·g^?1 in 0.9 wt % NaCl solution) due to the phosphorylation of PVA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

PAAS含量对吸水膨胀型PVO／OMTPV性能的影响

采用交联聚丙烯酸钠（PAAS）为吸水材料,通过动态硫化法制备了聚氯乙烯（PVC）j氯化聚乙烯橡胶（cM）热塑性硫化胶（TPV）,并对其力学性能、微观相态结构及吸水行为进行了研究。结果表明：在实验范围内,PVC／PAAS／CMTPV呈现出典型弹性体软而韧的应力应变行为;PAAS在基体中实现了均匀分散,且随着PAAS含量的增加,PVC／PAAS／CMTPV的力学性能呈下降趋势;PVC／PAAS／CMTPV的吸水性能随着PAAs的含量增加而显著提高,且在PAAS加入量为60phr时急剧增加;由于基体的屏蔽作用,PVC／PAAS／CMTPV没有出现明显的溶出现象。     

吸水膨胀型PVC/CM TPV的结构及性能

以交联聚丙烯酸钠(PAAS)为吸水材料,通过动态硫化法制备了聚氯乙烯(PVC)/氯化聚乙烯橡胶(CM)热塑性硫化胶(TPV),并对其力学性能、微观相态结构及吸水行为进行了研究。结果表明,在实验范围内,PVC/PAAS/CM TPV呈现出典型弹性体软而韧的应力-应变行为。当PVC/PAAS/CM的共混比为30/60/70时,TPV表现出了良好的综合性能,在室温条件下的蒸馏水中浸渍200h,吸水膨胀率可达2 000%,且在吸水100h时,吸水速率出现了峰值,干燥后的TPV几乎无失重。由试样的显微镜照片可见,PAAS在基体中实现了均匀分散,PVC/PAAS/CM TPV的拉伸断裂面较粗糙,PAAS颗粒的较大尺寸及较低的界面结合导致了TPV的较低力学性能。     

Fe3O4磁粉的合成与结构表征

采用化学共沉淀法制备纳米磁性Fe3O4粒子。选用NH3.H2O作为沉淀剂,加入到Fe2+和Fe3+的混合盐溶液中,制得了纳米磁性Fe3O4粒子。考察了影响产物粒径的一些实验因素。通过X-Ray谱图证实了产物结构特征,平均粒径在37 nm左右,平均晶粒度只有28 nm左右的均分散。     

PVA/Carbon Dot Nanocomposite Hydrogels for Simple Introduction of Ag Nanoparticles with Enhanced Antibacterial Activity

The introduction of nanomaterials to hydrogels is an effective way to improve the mechanical properties of hydrogels. Herein, carbon nanodot (C‐dot) as a new‐found excellent nanomaterial is first added to polyvinyl alcohol (PVA) hydrogel to prepare PVA/C‐dot hydrogel by freeze–thaw method. The appropriate size and plenty of surface functional groups make C‐dot an ideal nucleating agent for PVA crystallization, which leads to form a denser and more uniform cross‐linked network in PVA hydrogel, and in turn enhance the mechanical properties of PVA hydrogel. Compared to pure PVA hydrogel, about a 46.4% increase of tensile strength and 18.5% increase of elongation at break are achieved when the content of C‐dot in PVA/C‐dot hydrogel is 2 wt%, suggesting that C‐dot can effectively improve the mechanical properties of PVA hydrogel. Besides, C‐dot can endow PVA hydrogel with some new properties, such as fluorescence and reducibility. Herein, Ag nanoparticles are simply introduced and uniformly dispersed in PVA hydrogels with the help of reducibility of C‐dot, which can greatly enhance the antibacterial activity of PVA/C‐dot hydrogels, and enlarge their application potential in medical field.

     

Nickel and copper removal study from aqueous solution using new cationic poly[acrylamide/N,N‐DAMB/N,N‐DAPB] super absorbent hydrogel

A new cationic poly[acrylamide/N,N‐diallyl morpholinium bromide/N,N‐diallyl piperidinium bromide] super absorbent hydrogels (H1–H7) were prepared via microwave irradiated free radical cyclopolymerization using different composition. By the swelling study, hydrogel H1 is found to bear good swelling properties amongst all prepared hydrogels. The hydrogel H1 has been characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), and TGA analysis. A batch system was applied to study the adsorption of Ni(II) and Cu(II) from aqueous solutions by hydrogel H1. The effect of treatment time, pH of the medium, amount of adsorbent doses, and initial feed concentration of metal ion on adsorption of Ni(II) and Cu(II) from their solution were also investigated. Adsorption of Ni(II) and Cu(II) increases with the increase in treatment time, adsorbent doses, and initial feed concentration and decreases with the increase in pH of the medium. The desorption of metal ions were carried out using 1N HCl and 0.5N H₂SO_4. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011