温敏性水凝胶的制备及其对胃蛋白酶溶液的分离性能

通过溶液聚合法合成了丙烯酰胺(AM)与丙烯酸(AA)质量比不同的聚丙烯酰胺(PAM)与AA二元共聚水凝胶(PAM-AA),并研究了水凝胶的吸水性能和对胃蛋白酶溶液的浓缩性能。结果表明:水凝胶对蛋白质的浓缩性能与其吸水性能保持一致,单体AM与AA质量比为1∶1时具有最优浓缩倍率,为3.21倍;通过加入温敏性单体N-异丙基丙烯酰胺(NIPAM)对PAM-AA进行改性,发现NIPAM的加入会降低凝胶的吸水率,但使凝胶具有温敏性能,其低临界相转变温度(LCST)为32℃。利用温敏性凝胶的特性,在温度高于LCST时吸附蛋白质,温度低于LCST时释放蛋白质,可以实现对蛋白质较优浓缩,最高浓缩倍率可达3.72倍。PAM-AA对蛋白质浓缩通过吸水实现,而PAM-AA-NIPAM通过吸附蛋白质实现。     

近红外光响应氧化石墨烯/微凝胶复合智能水凝胶

设计合成了一种包含氧化石墨烯(GO)片层、聚(N-异丙基丙烯酰胺)(PNIPAM)微凝胶球体和PNIPAM链段的复合结构水凝胶。通过控制聚合时间得到负载双键且粒径不同的PNIPAM微凝胶,将其作为交联点与N-异丙基丙烯酰胺(NIPAM)聚合,GO作为纳米填料掺入水凝胶体系,GO片层上的含氧基团与NIPAM上的胺基产生氢键物理交联。此方法制备的复合水凝胶同时具有温度敏感和近红外光敏感特性,通过改变GO浓度、微凝胶的合成时间、NIPAM浓度等条件,水凝胶的光敏感性和温度敏感性得到提升。相比于传统PNIPAM水凝胶,此种复合水凝胶能够对光响应,实现非接触式控制形变,且响应速率快、响应程度高,可应用于光控开关等领域。     

近红外光响应氧化石墨烯/微凝胶复合智能水凝胶

设计合成了一种包含氧化石墨烯（GO）片层、聚（N-异丙基丙烯酰胺）（PNIPAM）微凝胶球体和PNIPAM链段的复合结构水凝胶。通过控制聚合时间得到负载双键且粒径不同的PNIPAM微凝胶,将其作为交联点与N-异丙基丙烯酰胺（NIPAM）聚合,GO作为纳米填料掺入水凝胶体系,GO片层上的含氧基团与NIPAM上的胺基产生氢键物理交联。此方法制备的复合水凝胶同时具有温度敏感和近红外光敏感特性,通过改变GO浓度、微凝胶的合成时间、NIPAM浓度等条件,水凝胶的光敏感性和温度敏感性得到提升。相比于传统PNIPAM水凝胶,此种复合水凝胶能够对光响应,实现非接触式控制形变,且响应速率快、响应程度高,可应用于光控开关等领域。     

温度/pH敏感型壳聚糖水凝胶的制备及其性能

以天然可降解高分子壳聚糖为载体,选择温度敏感单体N-异丙基丙烯酰胺以及pH敏感单体2-丙烯酰胺基-2-甲基丙磺酸,以偶氮二异丁腈为引发剂,N,N-亚甲基双丙烯酰胺为交联剂,通过自由基接枝共聚反应制备壳聚糖水凝胶。通过红外(IR)、扫描电镜(SEM)对其结构及形貌进行了表征,并探讨了影响水凝胶溶胀率的因素。结果表明,当单体配比NIPAM∶AMPS为6∶4、引发剂用量为单体总质量4%、交联剂用量为单体总质量的4%、反应温度为45℃形成的水凝胶在水中溶胀率可达95%左右。该水凝胶具有一定的温度和pH敏感性,预计在药物控释、组织工程、抗凝血材料等领域拥有广阔的应用前景。     

温度/pH敏感型壳聚糖水凝胶的制备及其性能

以天然可降解高分子壳聚糖为载体,选择温度敏感单体N-异丙基丙烯酰胺以及pH敏感单体2-丙烯酰胺基-2-甲基丙磺酸,以偶氮二异丁腈为引发剂,N,N-亚甲基双丙烯酰胺为交联剂,通过自由基接枝共聚反应制备壳聚糖水凝胶。通过红外(IR)、扫描电镜(SEM)对其结构及形貌进行了表征,并探讨了影响水凝胶溶胀率的因素。结果表明,当单体配比NIPAM∶AMPS为6∶4、引发剂用量为单体总质量4%、交联剂用量为单体总质量的4%、反应温度为45℃形成的水凝胶在水中溶胀率可达95%左右。该水凝胶具有一定的温度和pH敏感性,预计在药物控释、组织工程、抗凝血材料等领域拥有广阔的应用前景。     

pH值对N-异丙基丙烯酰胺与甲基丙烯酸共聚形成微凝胶的影响

在pH值为4．0和7．0的水介质中分别采用乳液聚合法使N-异丙基丙烯酰胺（NIPAM）和甲基丙烯酸（MAA）共聚,合成了具有温度／pH双重刺激响应性的P（NIPAM—CO—MAA）共聚微凝胶。傅立叶红外变换光谱、元素分析和电位滴定分析结果表明,在pH为4．0条件下合成的微凝胶中MAA单元含量偏高,微凝胶的粒径随着MAA用量的增加而增大,而pH为7．0时合成的微凝胶的粒径随着单体MAA用量的增加而减小。通过动态激光光散射测试P（NIPAM—CO—MAA）微凝胶的动力学直径随介质温度或pH值的变化关系发现,pH为4．0条件下合成的微凝胶具有更明显的pH刺激响应性,其温度刺激响应性受介质pH值的影响较大,表明MAA单元有可能更均匀地分布于微凝胶聚合物网络中。     

N-异丙基丙烯酰胺高分子水凝胶研究进展

N-异丙基丙烯酰胺基高分子水凝胶的研究进展做了综述。简要介绍了该类水凝胶的合成方法,重点分析了不同共聚单体及交联剂对水凝胶溶胀性能和环境响应性的影响,尤其是快速响应水凝胶的合成方法和N-异丙基丙烯酰胺/天然大分子水凝胶的特点。本文也简单介绍了该类水凝胶在不同领域内的应用。     

N-异丙基丙烯酰胺

N-异丙基丙烯酰胺为丙烯酰胺衍生物的单体,由于分子内有亲水性的酰胺基和疏水性的异丙基,其均相聚合物具有较低的临界溶解温度(LCST)等良好特性。由于其聚合物具有在32℃以下呈水溶性,32℃以上呈水不溶性这一特殊的溶解特性,正在开发用于制造某些感温性聚合物凝胶的原料。     

疏水型水凝胶的研究进展

将水溶性高分子的疏水改性技术应用于水凝胶研究领域,很大程度地改善了传统水凝胶的性能,因而成为目前水凝胶研究领域的热点课题之一。本文分别从化学水凝胶的疏水改性、嵌段共聚物水凝胶、接枝共聚物水凝胶等方面对疏水型水凝胶的研究进展进行了阐述。     

温敏性微凝胶的合成

对温度敏感性的高分子微凝胶的制备进行研究。采用无皂乳液聚合法,以N-异丙基丙烯酰胺(NIPAM)和N-乙烯基吡咯烷酮(NVP)为单体,丙烯酸(AA)为功能性共单体,过硫酸钾(KPS)为引发剂,N,N-亚甲基双丙烯酰胺(BIS)为交联剂,成功制备出了粒径均匀且具有良好分散稳定性的P(NIPAM-co-NVP)微凝胶。经过实验证明,所得微凝胶的粒径随单体添加量的增加而增大。所制备的微凝胶具有明显的温度敏感性,其低临界溶解温度(LCST)约为43℃(NIPAM=5 g)。     

淀粉及其衍生物的疏水化改性研究进展

淀粉及其衍生物通过引入不同的疏水性基团进行疏水化改性,改进了淀粉产品的应用性能,使之具有许多新的独特性能,更好的适应了特定的应用要求。综述了迄今原淀粉和羧甲基淀粉、羟乙基淀粉、阳离子淀粉以及两性淀粉几种不同的水溶性淀粉的疏水化改性方法,以及疏水基团的引入对产品主要性能的影响。介绍了疏水化改性淀粉衍生物在造纸、污水处理、土壤改良、涂料塑料工业等领域的应用和发展前景。     

疏水缔合型聚丙烯酰胺驱油剂的合成与性能评价

针对聚丙烯酰胺的研究现状及其应用中存在的问题,研制出一种抗温、抗盐性能较强,具有一定增粘性能的新型疏水缔合水溶性聚合物。本文通过较为简易的酸醇直接酯化法合成了一种丙烯酸正辛酯,确定了最适宜的合成条件;将该疏水单体与丙烯酰胺采用胶束共聚法合成了一种新型疏水缔合水溶性聚合物,考察了聚合物浓度、盐及温度等对疏水缔合共聚物溶液表观粘度的影响,实验结果表明,合成的聚合物具有良好的耐温抗盐性能。     

水溶性疏水缔合聚合物单体的合成

水溶性疏水缔合聚合物含有大量的亲水基团和少量的疏水基团,疏水基团间的疏水缔合作用使这种聚合物具有独特的增粘、抗剪切、耐温和耐盐的溶液性能,通常采用亲水单体和疏水单体共聚制备这类聚合物。对常用亲水单体AMPS及各类疏水单体如季铵盐不饱和单体AMPDAC和DAMAB、长链丙烯酸酯,N-烷基丙烯酰胺和N-芳烷基丙烯酰胺的合成进行了综述。     

温度及pH敏感生物水凝胶的研究

运用互穿网络技术,合成了具有温敏性的聚(N 异丙基丙烯酰胺)(PNIPAm)和生物大分子明胶(gelatin)的互穿网络聚合物(PNIPAm/Gelatinsemi IPN和PNIPAm/GelatinIPN)水凝胶,该水凝胶的最低临界溶液温度(LCST)与PNIPAm水凝胶的LCST基本相同,均为33℃左右,但在LCST以下的平衡溶胀率减小、相变区域略微变宽。在此基础上,通过N 异丙基丙烯酰胺(NIPAm)与丙烯酸(AAc)交联共聚,改变了水凝胶的LCST,在pH=4 0的缓冲溶液中,各水凝胶的溶胀行为基本一致,与AAc含量无关,LCST都为28℃左右;在pH>4 0的缓冲溶液中,LCST随AAc组分含量的增加而增加,但温敏性减小。同时,AAc的加入,使水凝胶具有pH敏感性,敏感点为pH=4 5左右。还考察了该水凝胶降解的特点:戊二醛(GA)交联后的明胶网络,保留了明胶的生物降解性,但互穿网络水凝胶在实验条件下几乎未被胃蛋白酶和胰蛋白酶降解,在pH=9 6的碱性条件下,水凝胶可发生化学降解。     

疏水基团改性聚丙烯酸的缔合作用和流变行为

采用旋转黏度计测试系列疏水改性聚丙烯酸水溶液的流变性能,用稠度系数和流动指数表征聚合物水溶液的表观粘度。研究了聚合物在水中的增粘作用,以及pH、疏水单体含量和疏水单体结构的影响。结果表明聚合物水溶液呈非牛顿流体性质,疏水改性聚丙烯酸则表现出pH敏感性;在改性聚丙烯酸中,如苯氧基(3乙氧基)乙基丙烯酸酯中的疏水基团含量0.16%时,稠度系数为5.82,是纯聚丙烯酸的23.5倍;疏水基团碳数的增加显著提高其增粘作用。研究的结果可为含疏水改性聚丙烯酸在印染污水中应用提供理论数据。     

Rheological properties of a hydrophobically modified anionic polymer: Effect of varying salinity and amount of hydrophobic moieties

Hydrophobically modified polyelectrolytes have been suggested as an alternative to the more commonly used polyelectrolytes in enhanced oil recovery (EOR) applications involving polymers. Compared to regular polyelectrolytes, the hydrophobically modified polyelectrolytes are known to be more stable at high salinities. In this study, we have investigated the influence of brine salinity and ionic composition for a series of six hydrophobically modified polyelectrolytes with the same polymer backbone, but with an increasing average number of hydrophobic groups per polymer molecule. Polymer characterization has been performed using a combination of steady‐state shear viscosity and dynamic oscillatory measurements. Hydrophobic interactions leading to a change in rheological properties was only observed above a threshold value for the concentration of hydrophobe. At the threshold value, salt‐induced hydrophobic interactions were observed. For higher concentrations of hydrophobe, high salinity solutions showed one order of magnitude increase in viscosity compared to the polymer without hydrophobic groups. This could partly be explained by an increase in elasticity. These findings have important implications for polymer selection for EOR. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43520.     

Hydrophobically associating polymers and their interactions with rod-like micelles

Several families of anionic and cationic hydrophobically associating acrylamide-based copolymers have been synthesized. This study focuses on the characterization in aqueous environments of water-soluble copolymers in which low levels of alkyl, i.e. methylene, units are incorporated into the polymer chain structure. These hydrophobic monomers have built-in surfactant character; therefore, no non-polymerizable surfactants are required in the preparation of these copolymer materials. These hydrophobically associating copolymers are shown to possess both polyelectrolyte and hydrophobic character, especially as the ionic strength of the solution is varied. The results confirm that, even at low concentrations of hydrophobe (typically ≤ 1 mol%), interesting solution properties are observed, i.e. enhanced rheology as compared to its non-associating parent, marked time-dependent rheology at low shear rates, ‘anti-polyelectrolyte effect’ in high-ionic-strength solutions and the ability to interact preferentially with hydrophobically associating rod-like micelles. These latter materials are capable of forming highly viscoelastic solutions themselves. The rheological properties of these latter solution mixtures are very sensitive to the fraction of each component in the mixture and to the length of the alkyl chain copolymerized into the acrylamide chain backbone.     

Investigation of swelling and controlled-release behaviors of hydrophobically modified poly(methacrylic acid) hydrogels

Using hydrophobic acrylic acid-2-ethylhexyl ester (AAEHE) as a comonomer of methacrylic acid (MAA), a series of hydrophobically modified (HM) poly(methacrylic acid) (PMAA) (HMPMAA) hydrogels were prepared by UV solution copolymerization and studied as controlled-release matrices. The result indicates that swelling degree of the HMPMAA hydrogels can sensitively respond to change in pH. However, the presence of hydrophobic AAEHE segments influences swelling kinetics of PMAA hydrogel evidently. Using p-hydroxyanisole (PHAS) as a model molecule, controlled-release behaviors of the HMPMAA hydrogels were investigated. It is found that the presence of hydrophobic AAEHE segments can markedly slow down the release rate of PHAS from PMAA-based hydrogels regardless of pH 1.4 or 7.4.     

Synthesis and aqueous solution behavior of hydrophobically modified polyelectrolytes

The hydrophobically modified polyelectrolytes were prepared by a micellar technique from acrylamide, n‐alkylacrylamides, and a third monomer, sodium acrylate or sodium 2‐acrylamide‐2‐methylpropanesulfonate. Synthesis and solution properties of the terpolymers were studied. In the synthesis process, the type and amount of surfactant and anionic monomers influenced their solution behavior greatly. The terpolymers showed strong synergistic viscosification effects between their ions and hydrophobic groups. Their aqueous brine solutions exhibit high viscosity at low polymer concentration and can maintain the viscosity during aging at a high temperature (80°C). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3552–3557, 2001     

Compressive moduli and network parameters of N‐isopropylacrylamide hydrogels copolymerized by monoesters of itaconic acid and crosslinked with tetraallylammonium bromide

The present study focuses on the mechanical properties of hydrophilically or hydrophobically modified poly(N‐isopropylacrylamide) (PNIPAAm) hydrogels, and all discussions on their improved mechanical strengths are based on the conformational effects of hydrophobic side chains attached to the comonomers and the structural differences between the crosslinkers. Three different types of monoalkyl itaconates, bearing octyl (Oc), cetyl (Ce), and cyclohexyl (CH) groups as comonomers, were used to prepare the copolymeric PNIPAAm hydrogels crosslinked with N,N′‐methylenebisacrylamide (BIS) and tetraallylammonium bromide (TAB) as neutral tetrafunctional and ionic octafunctional crosslinkers, respectively. The most striking result is the compressive E modulus of TAB‐crosslinked PNIPAAm hydrogel containing 10 mol % of mOcI. It reaches nearly 1.0 MPa and is independent of the temperature and pH of the swelling/shrinking medium. The result was discussed in terms of the inter/intramolecular interactions between hydrophobic octyl groups adopting a rod‐like conformation in the case of 25 °C/distilled deionized water (DDW) and 37 °C/DDW combinations. Further, it was observed that the electrostatic repulsive forces between the carboxylate groups on mOcI units could be suppressed even at 37 °C and pH 9 due to the rod‐like conformations of C₈H₁₇ groups. Its micrographs under bright‐field and polarized light supported the presence of an ordered anisotropic phase and multiple associations of extended, hydrophobic side chains. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45039.