用红外光谱研究具有互穿网络结构的pH/温度双重敏感性微凝胶的相转变行为

采用傅立叶变换红外光谱仪测试了由聚(N-异丙基丙烯酰胺)(PNIPA)和聚丙烯酸(PAA)两种聚合物网络形成的具有互穿聚合物网络结构(IPN)的pH/温度双重敏感性微凝胶D2O分散液,通过差谱技术对不同pH值和温度条件下的红外吸收光谱进行处理,研究微凝胶相转变过程中分子链微环境的变化.结果表明,随着D2O介质的pH值增...     

无皂种子分散聚合法制备单分散双重响应性微凝胶

以N-异丙基丙烯酰胺及2-乙烯基吡啶为主要单体, 采用无皂种子分散聚合法制备了单分散的、具有温度及pH双重响应性能的核-壳结构微凝胶, 并以扫描电镜及动态激光光散射等手段对微凝胶粒子的结构和性能进行了研究. 溶胀行为研究表明, 微凝胶粒子具有独立的互不干扰的温度及pH敏感性能, 其体积相变温度与纯聚N-异丙基丙烯酰胺(PNIPAM)凝胶基本一致, 说明局部分布的弱电离单体不会对PNIPAM凝胶的体积相变温度造成影响.     

智能纳米水凝胶的刺激响应性研究进展

智能纳米水凝胶在药物输送与可控释放、医学诊断、生物传感器、微反应器、催化剂载体等方面有良好的应用前景。结合本课题组近年来的研究成果,分别介绍了具有温度刺激响应性、pH刺激响应性、光刺激响应性、磁场刺激响应性、分子识别刺激响应性和多重刺激响应性智能纳米水凝胶的研究进展。另外,对这几种智能纳米水凝胶目前存在的问题和今后的发展方向提出了一些粗浅的看法。     

基于温度/pH双响应的聚合物表面活性剂调控嵌段共聚物微球形貌

研发响应多重外界刺激而改变形貌的嵌段共聚物微球对发展新型智能材料具有重要意义.本工作提出了一种温度/pH双响应嵌段共聚物微球形貌转变的策略.在利用乳液挥发法制备聚苯乙烯-b-聚(4-乙烯基吡啶)(PS-b-P4VP)微球时,引入温度/pH双响应的聚丙烯酸-b-聚(N-异丙基丙烯酰胺)(PAA-b-PNIPAM)作为表面活性剂,通过调控实验温度以及水相的pH值,实现了PS-b-P4VP微球在蚕蛹状、草莓状、洋葱状等形貌之间的转变.这种独特的形貌转变依赖于温度/pH调控的PAA-b-PNIPAM的亲疏水性转变,以及由此导致的表面活性剂在界面分布位置的改变,进而改变了油水界面的界面选择性以及微球的形貌.通过改变PAA-b-PNIPAM的质量分数、PAA和PNIPAM的嵌段比,系统地研究了温度/pH对PS-b-P4VP微球形貌转变机制的影响.提供了一种温度/pH双响应的微球形貌转变的策略,有望在药物释放、智能传感等领域发挥重要作用.     

聚合物微凝胶研究进展

微凝胶是一种具有交联网络结构的聚合物胶体粒子,处于良好溶剂中的刺激响应型微凝胶会受某些外界环境的刺激,产生溶胀-消溶胀响应行为,具有快速、可逆的相变特性和较好的生物相容性。本文综述了近年来国内外微凝胶的研究现状,介绍了互穿网络型、核-壳型和含有纳米粒子的复合型微凝胶的结构、特性和制备方法,阐述了微凝胶在药物控制释放、催化反应体系、生物传感器等方面的应用,探讨了聚合物微凝胶领域的研究前景和所面临的问题。     

微凝胶胶体晶体研究进展

Poly(N-isopropylacrylamide)(PNIPAM)微凝胶粒子是一种软的胶体粒子.和单分散的SiO_2、PS、PMMA等硬的胶体粒子一样,单分散的PNIPAM微凝胶粒子也可以自组装成为高度有序的胶体晶体.微凝胶粒子软物质的特性及其对外部刺激的响应性赋予其不同于硬球的组装行为.微凝胶胶体晶体的高度有序结构及其刺激响应性使其在诸多领域有重要用途.本文分别介绍了三维及二维微凝胶胶体晶体组装的研究进展,并对已开发的基于微凝胶胶体晶体的应用进行了总结.     

壳聚糖·聚丙烯酸配合物半互穿聚合物网络膜及其对pH和离子的刺激响应

壳聚糖·聚丙烯酸配合物半互穿聚合物网络膜及其对ｐＨ和离子的刺激响应李文俊王汉夫卢玉华汪志亮钟伟（复旦大学高分子科学系聚合物分子工程开放实验室上海２００４３３）关键词高分子间配合物，互穿聚合物网络（ＩＰＮ），水凝胶，壳聚糖，刺激响应敏感性水凝胶是一种...     

环糊精超分子水凝胶*

本文综述了近年来基于环糊精包合作用的超分子水凝胶的研究进展,主要包括：环糊精与线性、星型、接枝、超支化聚合物包合形成的多聚(准)轮烷自组装制备超分子物理凝胶及功能化多聚(准)轮烷经交联反应制备超分子化学凝胶;环糊精、环糊精二聚体及其水溶性聚合物与带疏水性侧基的聚合物经“锁-钥匙”包合作用形成超分子物理凝胶;及其在药物、基因释放载体与组织工程支架中的应用。着重介绍了剪切、温度、pH值、光等刺激-响应性超分子水凝胶的设计与制备。     

丝胶基半互穿温敏凝胶的合成及其溶胀行为的研究

采用半互穿网络技术, 将具有生物相容性的丝胶蛋白(silk sericin)作为第二网络进入聚(N-异丙基丙烯酰胺)(PNIPAM)水凝胶网络中, 在水溶液中制备得到具有半互穿网络结构的丝胶基温敏水凝胶(SS/PNIPAM semi-IPNs). 采用称重法研究了产物的(消)溶胀、温度敏感性、最大溶胀度及脉冲响应行为; 利用扫描电镜(SEM), 差示扫描量热仪(DSC)和动态热机械分析仪(DMA)分别考察了产物的内部形态、热相转变行为和其储能模量随温度的变化. 结果表明: 具有较高亲水性的丝胶蛋白的引入增大了semi-IPNs水凝胶的内部孔径, 导致SS/PNIPAM半互穿水凝胶的溶胀度增加, 并且其储能模量随温度变化更明显. 相比于纯PNIPAM水凝胶, 半互穿水凝胶的消溶胀速率和低临界溶解温度(LCST)变化不大.     

PVA增强P(AAEA-co-AA)温度敏感性水凝胶的合成及其性能研究

以4-乙酰基丙烯酰乙酸乙酯(AAEA)、丙烯酸(AA)以及PVA为原料, 通过自由基溶液聚合法, 制备了PVA-P(AAEA-co-AA)半穿网络型(s-IPN)水凝胶. 红外分析表明, AAEA主要以烯醇式结构存在, 并且由于PAAEA, PAA以及PVA之间较强的氢键作用, 使得PAAEA以及PVA分子上的C-O伸缩振动吸收峰移向了低波数处. 电镜分析表明, PVA能贯穿于P(AAEA-co-AA)交联网络中, 从而有效阻碍凝胶的相分离|而XRD研究发现, 当PVA用量较少时, PVA能均匀的贯穿于凝胶网络中, 形成完善的互穿网络结构, 当PVA用量过高时, PVA不能有效地贯穿于聚合物交联网络中而出现结晶. 采用DSC对s-IPN水凝胶的体积相转变进行了研究, 结果表明, 该s-IPN水凝胶的体积相转变温度(VPTT)在54.0至57.8 ℃之间, 并且随着PVA用量的增加, 凝胶的VPTT逐渐升高. 研究了该s-IPN水凝胶的抗压缩性能, 结果表明, PVA与P(AAEA-co-AA)形成的半互穿网络结构能有效提高凝胶的抗压缩强度, 其最大抗压缩强度可达8.4 MPa. 对凝胶的温度敏感性研究发现, 当外界温度低于VPTT时, 凝胶能保持溶胀状态|而当温度高于VPTT时, 凝胶的平衡溶胀度迅速下降, 表现为温度敏感性.     

Synthesis and light scattering study of microgels with interpenetrating polymer networks

Monodispersed microgels composed of poly(acrylic acid) (PAAc) and poly(N-isopropylacrylamide) (PNIPAM) interpenetrating polymer networks (IPN) were synthesized by a two-step method, first preparing PNIPAM microgel and then polymerizing acrylic acid that interpenetrates into the PNIPAM network. The growth kinetics of the IPN particle formation was obtained by measuring the turbidity and particle hydrodynamic radius (Rh) as a function of reaction time. IPN and PNIPAM microgels were characterized and compared by dynamic and static light scattering techniques. The concentrated aqueous solutions of the PNIPAM-PAAc IPN microgels exhibit an inverse thermoreversible gelation. In contrast to polymer solutions of poly(NIPAM-co-AAc) that have the inverse thermoreversible gelation, our system can self-assemble into an ordered structure, displaying bright colors. Furthermore, IPN microgels undergo the reversible volume phase transitions in response to both pH and temperature changes associated with PAAc and PNIPAM networks, respectively.     

核壳结构葡萄糖敏感微凝胶的制备

用先合成聚N-异丙基丙烯酰胺(PNIPAM)微凝胶核再包一层N-异丙基丙烯酰胺/丙烯酸共聚物(P(NIPAM-co-AA))壳的办法合成了一系列核壳结构微凝胶.微凝胶壳层厚度随投入的壳储备溶液的增加而增加.研究了pH=3.5时核壳微凝胶的温敏体积相转变行为.由于PNIPAM核和P(NIPAM-co-AA)壳的相转变温度很接近,因此只观察到一个相转变.在EDC催化下使3-氨基苯硼酸与壳层中的羧基反应,将苯硼酸基(PBA)引入微凝胶,得到核为PNIPAM、壳为P(NIPAM-co-AMPBA)的核壳结构微凝胶.改性后的微凝胶表现出3个体积相转变过程.其中第一个对应于P(NIPAM-co-AMPBA)壳层的体积相转变.第二和第三个则是PNIPAM核的相转变过程.由于在沉淀聚合时交联剂BIS反应性更大,PNIPAM核结构不均一,形成BIS含量高的"核"和BIS含量低的"壳".BIS含量低的"壳"被一层疏水的P(NIPAM-co-AMPBA)壳包裹,拉大了其与"核"的相转变温度的差别,因此随着温度升高表现出两个相转变过程.PBA改性的微凝胶同样表现出葡萄糖敏感性,但在葡萄糖存在下溶胀度的改变较小.     

相转变温度范围窄的聚(N-异丙基丙烯酰胺)温敏性微凝胶

采用间歇式、半间歇式和连续式无皂乳液聚合(SFEP)法合成温敏性聚(N-异丙基丙烯酰胺)(PNIPAM)微凝胶。连续式或半间歇式SFEP法合成的PNIPAM微凝胶相转变温度范围明显地比间歇式SFEP法合成的窄,其中又以连续式SFEP法的效果最明显。相同交联剂用量的情况下,连续式SFEP法合成的PNIPAM微凝胶的粒径和溶胀比最大,而间歇式SFEP法合成的最小。通过研究微凝胶合成过程中溶胀比随反应时间的变化关系,证明了连续式或半间歇式SFEP法合成的PNIPAM微凝胶具有比较均匀的内部交联结构。     

聚(N-异丙基丙烯酰胺)水凝胶微球体积相变的研究

窄分散的聚（Ｎ 异丙基丙烯酰胺）水凝胶微球用乳液聚合方法制备，并用动态和静态光散射对其体积相变进行了研究．与水中聚（Ｎ 异丙基丙烯酰胺）线性单链比较，水中凝胶微球的体积相变温度较高，对温度的响应比较平缓．相变是连续的，有别于大块凝胶非连续的体积变化．在体积相变过程中，凝胶微球始终是密度均一的热力学稳定球体．从相变过程网络密度的变化可以确定，绝大部分的水在收缩过程被排了出来，但在紧缩的凝胶微球中仍含有约７０％的水．     

AuNPs/PNIPAM复合颗粒的制备及其温敏性质

将金纳米颗粒(AuNPs)组装到聚N-异丙基丙烯酰胺(PNIPAM)水凝胶微球表面制备出AuNPs/PNIPAM复合颗粒. 将PNIPAM 凝胶的温敏特性与AuNPs的光学性质结合, 通过改变温度调节AuNPs的局部表面等离子共振(LSPR)吸收峰位置. 研究结果表明, 温度升高使AuNPs的LSPR吸收峰发生红移, 并且这种效应是可逆的. 同时发现, AuNPs的光学性质还可以作为表征PNIPAM水凝胶微球温敏行为的一种手段. 利用透射电镜、紫外-可见光谱仪及动态光散射仪对AuNPs/PNIPAM复合颗粒的形貌、光学性质、粒径变化等进行了分析.     

聚丙烯酰胺/聚异丙基丙烯酰胺互穿网络水凝胶的制备与性能

采用分步法用电子加速器辐射合成了聚丙烯酰胺(PAAm)/聚异丙基丙烯酰胺(PNIPAAm)互穿网络水凝胶,并考察了温度、pH值、离子强度对其溶胀性能的影响.研究表明:互穿水凝胶具有温度敏感性,且其体积相变与互穿网络中PAAm和PNIPAAm含量有关,随着网络中PAAm含量的增加水凝胶的体积相变趋于平缓,可以通过改变PAAm和PNIPAAm的组成比来控制水凝胶的体积相变行为.此外,互穿水凝胶还具有pH敏感性和一定的抗盐性.     

Influence of charge density on the swelling of colloidal poly(N-isopropylacrylamide-co-acrylic acid) microgels

The volume phase transition of colloidal poly(N-isopropylacrylamide-co-acrylic acid) microgels depends in a complex way on the effective charge density within the polymer network. A series of monodisperse PNIPAM/AAc microgels with different content of acrylic acid were synthesized by surfactant-free emulsion polymerization employing sonication instead of a conventional stirring technique. Subsequently, the colloids were characterized by dynamic light scattering and electron microscopy. Potentiometric titrations provided the amount of carboxyl groups incorporated into the copolymer. The effective charge density was systematically controlled by the content of acrylic acid monomers, the pH value of the suspension, and the salt concentration. The hydrodynamic dimensions of the microgels have been measured by dynamic light scattering. The swelling/deswelling behavior is determined by the delicate balance between hydrophobic attraction of NIPAM and the repulsive electrostatic interactions of the carboxylate group of the acrylic acid moieties. Compared to their macroscopic counterparts the charged microgel particles show a significantly different swelling/deswelling behavior. This manifests in the occurrence of a two-step volume phase-transition process with increasing acrylic acid content. Hydrogen bonding has to be considered to understand this two step volume phase transition uniquely observed for colloidal microgels. Another interesting phenomenon presented here is the reversible formation of well-defined aggregates at low pH and under high salt conditions.     

Temperature, pH, and ionic strength induced changes of the swelling behavior of PNIPAM-poly(allylacetic acid) copolymer microgels

The volume phase transition of colloidal microgels made of N-isopropylacrylamide (NIPAM) is well-studied and it is known that the transition temperature can be influenced by copolymerization. A series of poly( N-isopropylacrylamide- co-allylacetic acid) copolymers with different contents of allylacetic acid (AAA) was synthesized by means of a simple radical polymerization approach. The thermoresponsive behavior of these particles was studied using dynamic light scattering (DLS). Further characterization was done by employing transmission electron microscopy (TEM) and zeta potential measurements. TEM observations reveal the approximately spherical shape and low polydispersity of the copolymer particles. In addition, the measured zeta potentials provide information about the relative surface charge. Since these copolymers are much more sensitive to external stimuli such as pH and ionic strength than their pure PNIPAM counterparts, the volume phase transition was investigated at two different pH values and various salt concentrations. At pH 10 for the copolymer microgels with the highest AAA content, a significant shift of the volume phase transition temperature toward higher values is found. For higher AAA content, a change in pH from 8 to 10 can induce a change in radius of up to 100 nm making the particles interesting as pH controlled actuators.     

Structure and pH‐sensitive properties of poly (vinylidene fluoride) membrane changed by blending poly (acrylic acid) microgels

pH‐sensitive poly (vinylidene fluoride) (PVDF)/poly (acrylic acid) (PAA) microgels membranes are prepared by phase inversion of the N, N‐dimethylformamide solution containing PAA microgels and PVDF in aqueous solution. The composition and structure of the blend membrane are investigated by Fourier transform infrared spectra, X‐ray photoelectron spectroscopy measurements, thermo gravimetric analysis, field‐emission scanning electron microscope and atomic force microscope. The results indicate the surface and cross section of the blend membranes have a porous structure with PAA microgels immobilized inside the pore and on the membrane surface. The blend PVDF membranes exhibit pH‐sensitive water flux, with the most drastic change in permeability observed between pH 3.7 and 6.3. The blend membranes are fouled by bovine serum albumin, and their antifouling property is enhanced by increasing PAA microgels, mainly derived from the improved hydrophilic property. Copyright © 2013 John Wiley & Sons, Ltd.