多孔温敏凝胶的制备及性能测试

N-异丙基丙烯酰胺(NIPA)具有优良的温敏智能特性和记忆效应,目前已在药物缓释、物料分离、酶的固定、生物医学材料等领域得到广泛应用.本文以不同分子量的聚乙二醇(PEG)为致孔剂,在18℃下制备了多孔结构的共聚凝胶,并考察了聚乙二醇(PEG)分子量和用量对凝胶溶胀率的影响.研究表明,PEG的加入使凝胶形成多孔结构,多孔...     

N-异丙基丙烯酰胺类环境敏感性水凝胶的聚合及应用研究进展

N-异丙基丙烯酰胺(NIPA)类水凝胶是典型的温敏性凝胶,重点介绍了NIPA的均聚反应及其与天然高分子的复合,并对其在药物释放、物质分离及生物医用材料体系中的研究进展进行了总结。     

聚N-异丙基丙烯酰胺类凝胶及其温敏性和酸敏性的研究

以N-异丙基丙烯酰胺为基础制成四种凝胶:①N-异丙基丙烯酰胺均聚凝胶;②N-异丙基丙烯酰胺与甲基丙烯酰胺共聚凝胶;③N-异丙基丙烯酰胺与甲基丙烯酸钠共聚凝胶;④N-异丙基丙烯酰胺与丙烯酰胺共聚,经水解生成的凝胶。探讨了引发剂、促进剂和交联剂及单体总浓度对凝胶化时间或凝胶的溶胀性能的影响,以及凝胶的温敏与酸敏相变条件。设计了温敏凝胶萃取过程,并对牛血清蛋白、碱性蛋白酶以及某种人体激素溶液进行浓缩实验。结果表明其具有良好的实用前景。     

pH-温度双重敏感性水凝胶的制备及溶胀性能研究

制备具有pH及温度双重敏感性水凝胶。通过自由基聚合反应制备出NIPAM-co-PMAA水凝胶材料。考察不同单体甲基丙烯酸(MAA)和N-异丙基丙烯酰胺(NIPA)配比对pH和温度的响应能力,探究其溶胀性能。结果表明,不同配比的水凝胶具有双重敏感性。NIPA含量不同时,对于LSCT温度有影响,MAA含量不同时,在酸性条件下溶胀率较大。结论,NIPAM-co-PMAA水凝胶有望成为药物载体。     

P(NIPA/AMPS)接枝改性UHMWPE织物的性能

通过氩微波低温等离子体引发、紫外辐射聚合将N-异丙基丙烯酰胺(NIPA)和2-丙烯酰胺-2甲基丙磺酸(AMPS)的二元共聚物[P(NIPA/AMPS)]接枝到超高相对分子质量聚乙烯(UHMWPE)织物,研究了织物的温敏性、pH敏感性及成孔剂CaCO3的加入对其响应速度的影响。结果表明,在紫外光照射强度一定时,AMPS浓度、交联剂浓度是影响织物接枝率的主要因素。优化的接枝工艺条件为AMPS质量分数50%,交联剂质量分数5%,等离子体处理时间6 m in,处理功率240 W。该织物最低临界共熔温度约为38℃,其溶胀比随温度、pH值变化而变化,且其温敏性吸水-失水动力学曲线呈现快速响应性。该织物的湿态静水压为1 500 Pa,干态透气性为482 L/(m2.s),干态透湿性为2 010 g/(m2.d),吸水后具有很好的阻水性能,干态后仍保留了一定透湿、透气性。     

NIPAAM共聚物的合成与应用研究进展

N-异丙基丙烯酰胺(NIPAAM)由于具有独特的温敏性能,其共聚物作为一种智能材料被广泛应用。综述了NIPAAM的温敏机理和系列NIPAAM共聚物的合成方法,对其在药物运输、物料分离、细胞附着脱附和色谱分析等领域的应用进行了介绍,并简要评述了NIPAAM共聚物的研究开发前景。     

NIPAAm的合成路线改进及应用

引　言聚N 异丙基丙烯酰胺p(NIPAAm)类具有特殊的温敏性能 ,其LCST (低临界溶解温度 )在 32℃左右 ,在温敏薄膜、物料分离、感应件、仿生及医学等领域具有广泛的应用前景[1～ 4 ] .特别是在物质的浓缩与分离方面具有很高的工业应用价值 .因此研究单体N 异丙基丙烯酰胺 (NIPAAm)的生产路线就显得极为重要 .NIPAAm合成路线有多种 ,如胺与不饱和酰氯反应、不饱和烯腈或烯胺的N 烷基化反应、贝克曼重排反应等[5,6 ] .其中Plaut[7] 、金曼蓉[8] 、陈文明[9] 等分别报道了丙烯腈与异丙醇在浓硫酸存在下NIPAAm的合成方法 ,该法对硫酸用…     

改性凝胶的制备及溶胀性能研究

温敏性材料N-异丙基丙烯酰胺（NIPA）作为新型智能材料,在化学药物分离方面的应用是研究者关注的焦点。手性单体N-（L-1-乙氧甲酰基-2-苯基）丙烯酰胺（AAc-L-PheEt）与NIPA聚合制备手性共聚水凝胶后水解,得到P（NIPA-co-AAc-L-Phe）凝胶。研究改性后的手性凝胶发现：手性凝胶不仅有良好的温度敏感性,同时具备pH敏感型性能。     

聚N-异丙基丙烯酰胺/甲基丙烯酸聚乙二醇酯温敏性水凝胶的制备及性能研究

采用自由基共聚方法合成了一种新型温敏性共聚物聚甲基丙烯酸聚乙二醇酯-N-异丙基丙烯酰胺P(NIPAAm-PEG-MA).实验结果表明,在一定的温度范围内,共聚物水凝胶的溶胀率随温度升高、PEGMA含量的减少呈下降趋势,并随交联剂用量的变化存在一最大值,表现出明显的温敏行为.     

温敏型水凝胶的制备及溶胀特性

采用N-异丙基丙烯酰胺(NIPA)与N-乙烯基-2-吡咯烷酮(NVP)为共聚单体,以N,N-亚甲基双丙烯酰胺(BIS)为交联剂,过硫酸钾(KPS)为引发剂,通过化学交联的方法在水溶液中制备出P(NIPA-co-NVP)共聚物水凝胶。分别探讨了单体配比、交联剂用量等实验条件对水凝胶的温敏特性和溶胀性能的影响。利用傅里叶红外(FT-IR)对共聚物水凝胶的结构进行了表征。通过实验可知:当交联剂BIS和引发剂KPS分别为单体用量的5%和0.8%,制备的水凝胶具有较高的转化率、较好的机械强度和共聚性质。共聚物水凝胶中NVP含量越高,溶胀率越大,升温时溶胀率下降程度越大,自然条件下脱水速率越快;BIS用量越大,溶胀率越小,保水率越高,需要更长时间达到溶胀平衡。     

Uptake of zinc,nickel, and chromium by N-isopropyl acrylamide polymer gels

Pure N-isopropyl acrylamide (NIPA) polymer gel and NIPA copolymers containing 2-acrylamido-2-methylpropane sulfonic acid (AMPS), 2-acetamidoacrylic acid (AAA), and acrylic acid (AA) were prepared and evaluated with respect to their capability for taking up zinc, nickel, and chromium ions from solutions. AAA-containing NIPA gels were found to take up these metal ions most efficiently. Titration of these gels verified the strong acidic nature of the AMPS–NIPA gel and the weakly acidic nature of the AA–NIPA and AAA–NIPA gels. The ion-exchange capacities, derived from the titration curves, were, however, rather low in all cases. NIPA gels are known to collapse at temperatures about 32°C. This, however, was found to have no effect on the ion-exchange behavior of the gels. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:355–362, 1998     

Rheological properties of poly(ethylene glycol)/poly(N‐isopropylacrylamide‐co‐2‐acrylamido‐2‐methylpropanesulphonic acid) semi‐interpenetrating networks

For the increasing demands of multifunctional materials in applications such as drug delivery system, a pH‐ and temperature‐responsive polyelectrolyte copolymer gel system was studied using rheometry. Rheological properties, determined by plate–plate rheometry in oscillatory shear, of hydrogels formed by free radical initiated copolymerization of N‐isopropylacrylamide (NIPA) and 2‐acrylamido‐2‐methylpropanesulphonic acid (AMPS) in the presence of methylene bisacrylamide (MBAA) as crosslinker are compared with the properties of semi‐interpenetrating network (SIPN) polyelectrolyte gels made by incorporation of poly(ethylene glycol) with molar mass 6000 g mol^?1 (PEG6000). Based on our systematic studies for this PEG/SIPN system, the effects of initiator and crosslinker concentration, relative proportions of comonomer units in the main chains, PEG6000 content and temperature on viscoelastic properties, unusual high storage moduli at small strain for the SIPN were discussed. The SIPN gel with characteristics of PEG molecules as well as pH and temperature responsiveness from AMPS and NIPA units has potential application in drug delivery system design. Ice‐like rheological behavior of the PEG/AMPS‐NIPA SIPN gels at low temperature was first time reported and water remains homogeneous without phase separation in PEG/AMPS‐NIPA SIPN hydrogels at low temperature may be considered as an ideal candidate for water storage material. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Adsorption of ammonium and nitrate ions by poly(N‐isopropylacrylamide) gel and poly(N‐isopropylacrylamide‐co‐chlorophyllin) gel in different states

The adsorption of ammonium and nitrate by temperature‐stimulus‐responsive poly(N‐isopropylacrylamide) (NIPA) gel and poly(N‐isopropylacrylamide‐co‐chlorophyllin) (NIPA‐CH) gel in different states was investigated. Both the NIPA gel and NIPA‐CH gel could adsorb ammonium and nitrate in a swollen state (swollen gel) and a swelling state (swelling gel), and they adsorbed ammonium more than nitrate. When the gels were shrinking (shrinking gel), they could adsorb a little ammonium from solution, but when the gels were in a shrunken state (shrunken gel), they hardly adsorbed ammonium. The adsorption of both ammonium and nitrate increased for the swelling NIPA gel in comparison with the swollen gel. The NIPA‐CH gel was the opposite in this respect. The difference in the amounts of adsorption of ammonium and nitrate by the swollen and swelling NIPA‐CH gels was more significant than that of the NIPA gels. It was suggested that ions such as ammonium and nitrate could not diffuse into the gels freely. The adsorption of ammonium and nitrate was affected not only by the phase transitions of the gels but also by the electrical charges. The experimental results for the adsorption of ammonium and nitrate during the volume changes of the gels imply that if the gels are applied to the immobilization of microorganisms, they may improve mass transfer between the immobilization matrix and bulk liquid under cyclic temperature changes and promote reactions of the immobilized microorganisms, especially the nitrification of nitrifying bacteria immobilized by the NIPA‐CH gel. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2367–2372, 2005     

Raman microimaging study of interfacial profiles of hydrogels

A Raman microimaging technique was used to directly observe the interfacial profile between N-isopropylacrylamide (NIPA) and polyacrylamide (PAAM) hydrogels in water. The joined hydrogels are called bigels and are synthesized by penetrating the PAAM gel into a part of the NIPA gel network. The bigel strip contains about 97 wt % water at room temperature. The study reveals how different manufacturing parameters, such as the drying time of the NIPA substrate and the diffusion time of the PAAM pregel solution into the NIPA layer, influence the properties and extent of the bigel interface. The interface becomes thicker with increased drying time. Specifically, the average interfacial thickness of the interface after 2 h of drying is about 28 μm, but increases to 156 μm after 16 h of drying time. The extent of the interface is independent of the PAAM diffusion time. The penetration of the PAAM pregel solution into the pores of the NIPA gel is completed in less than 30 min. The topography of the surface can be well characterized by a Gaussian function with the correlation length describing the size of the interfacial region. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1040–1046;2001     

Characteristic role of crosslinker on thermally induced volumetric contraction–expansion processes in poly(N‐isopropylacrylamide) networks and water systems

In this work, the degree of crosslinking on the volumetric contraction–expansion processes of hydrogels made of poly(N‐isopropylacrylamide) (NIPA) (initial amount: C_m) with varied amount (z) of crosslinking agent methylene‐bis‐acrylamide (BIS) in reference to most commonly used NIPA gel that was synthesized with C_m = 700 mM and z = 8.6 mM was investigated by applying our recently developed pycnometry. We focused on characteristic role of four polymeric NIPA residues directly bonded to a single BIS molecule by evaluating the total volume of gels per four NIPA residues directly bonded to a BIS molecule, plus associated water [ν_sp(gel)(NIPA)_bonded)(T)], and the corresponding number of water molecules per four NIPA residues [N_s(gel)(NIPA)_bonded)(T)]. We elucidated how these quantities characteristically contribute to changes in the volumetric contraction–expansion processes of hydrogels. A comparison of these quantities with the corresponding quantities for (NIPA)_unbonded residues clearly revealed a significant structural difference between (NIPA)_bonded and (NIPA)_unbonded. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Porous poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) gels polymerized in mixed solvents of water and <Emphasis Type="Italic">N,N</Emphasis>-dimethylformamide

The structures of gels polymerized using a mixed solvent that induces cononsolvency during the free radical polymerization were investigated.N,N -isopropylacrylamide (NIPA) gels were polymerized in water and N,N-dimethylformamide (DMF) mixtures. The NIPA gels can have homogeneous/heterogeneous structures depending on the mole fraction of DMF, x_D. The NIPA gel synthesized at x_D = ca. 0.25 was opaque in appearance, and its porous structure was observed by the SEM micrograph; the porous structure is formed as the aggregates of microgels phase-separated due to the cononsolvency. The porous NIPA gels achieve a very rapid shrinking rate in response to the temperature jump, which are desirable for their applications.     

Fabrication of amphiphilic copolymeric gels with enhanced activity of immobilized enzymes in organic media

Novel amphiphilic copolymeric gels were developed to immobilize lipase. NIPA‐co‐PEGMEA gels were prepared by copolymerizing N‐isopropylacrylamide (NIPA) as a thermosensitive and amphiphilic component and poly(ethylene glycol) methyl ether acrylate (PEGMEA) as a hydrophilic component in aqueous media. The gels can absorb organic solvents at temperatures higher than the lower critical solution temperature owing to the thermosensitive and amphiphilic properties of poly(NIPA). The lipase immobilized within the NIPA‐co‐PEGMEA gel, which had a NIPA : PEGMEA composition of 950 : 50 mol/m³, successfully catalyzed the esterification of oleic acid and ethanol without loss of activity during repeated use within 20–40°C. The activity of the immobilized lipase was considerably higher than that of free lipase. The NIPA‐co‐PEGMEA gels provide a structure that allows the immobilized lipase to work actively in an aqueous environment and with the dispersed state of the lipase in the gels. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41905.     

Thermo-responsive poly(N-isopropylacrylamide) gel containing polymeric surfactant poly(2-(methacryloyloxyl)decylphosphate): correlation between rapid collapsing characters and micelles of polymeric surfactant

This paper deals with a thermo-responsive poly(N-isopropylacrylamide) (NIPA) gel containing a polymeric surfactant poly(2-(methacryloyloxyl)decylphosphate) (PMDP) which shows rapid volume change above phase transition temperature at ca. 34 degrees C. Based on the measurements of dye-solubilization, it was suggested that intra-molecular micelles of the polymeric surfactant PMDP are inside NIPA gel-network. It is concluded that the intra-molecular micelles of polymeric surfactant involving NIPA chains may play crucial role in the rapid collapse of the NIPA-PMDP gel at the phase transition temperature.