聚乙烯醇/聚丙烯酸水凝胶的电刺激响应性研究

通过冰冻－解冻循环方法制备了机理交联水凝胶聚乙烯醇（PVA）／聚丙烯酸（PAA），研究了该水凝胶在直流电场作用下的弯曲响应性质，考察不同浓度和组成的凝胶在0．01mol/L Na2Co3电解质水溶液中，。作用电场的电场强度对凝胶弯曲速率的影响，以及电解质溶液的浓度对凝胶弯曲速率的影响，初步探索了凝胶在电场作用下的弯曲机理。     

明胶-海藻酸钠半互穿聚合物网络膜及其电刺激响应行为的研究

制备了明胶-海藻酸钠半互穿聚合物网络膜，研究了膜的溶胀吸水率及其电刺激响应行为。结果表明海藻酸钠的引入可大大提高明胶的吸水率，在NaCl溶液中，该半互穿聚合物网络水凝胶膜在非接触直流电场作用下向电场负极弯曲，其弯曲速度及弯曲偏转量受外加电场强度和膜中聚离子浓度的影响。在循环电场作用下，膜的弯曲响应行为具有良好的可逆性。通过聚电解质凝胶弯曲理论初步解释了其弯曲机理。     

黄原胶/聚乙烯醇互穿网络水凝胶的电刺激响应行为

以戊二醛为交联剂,制备了黄原胶/聚乙烯醇(XG/PVA)互穿聚合物网络水凝胶,并研究了其吸水率、力学性能和电刺激响应行为。结果表明,在NaCl溶液中,该水凝胶的平衡溶胀比随NaCl溶液离子强度增大而减小,随pH值的增大而增大,当pH≥7时基本保持不变;经离子强度为0.01 mol/L NaCl溶液充分溶胀的XG/PVA互穿聚合物网络水凝胶其弹性模量为0.9844 MPa,拉伸强度为1.5691 MPa,断裂伸长率为1.60;在非接触的直流电场作用下,于NaCl溶液中,该水凝胶发生弯曲,凝胶的弯曲速度和弯曲偏转程度随外加电场的增加而增大;NaCl溶液离子强度对凝胶弯曲行为产生影响,当溶液离子强度I≤0.05时,凝胶向电场负极弯曲,当溶液离子强度I≥0.05时凝胶向电场正极弯曲;在循环电场作用下,其弯曲响应行为具有良好的可逆性。     

黄原胶/聚乙烯醇互穿网络水凝胶的电刺激响应行为EI北大核心CSCD

以戊二醛为交联剂,制备了黄原胶/聚乙烯醇(XG/PVA)互穿聚合物网络水凝胶,并研究了其吸水率、力学性能和电刺激响应行为。结果表明,在NaCl溶液中,该水凝胶的平衡溶胀比随NaCl溶液离子强度增大而减小,随pH值的增大而增大,当pH≥7时基本保持不变;经离子强度为0.01 mol/L NaCl溶液充分溶胀的XG/PVA互穿聚合物网络水凝胶其弹性模量为0.9844 MPa,拉伸强度为1.5691 MPa,断裂伸长率为1.60;在非接触的直流电场作用下,于NaCl溶液中,该水凝胶发生弯曲,凝胶的弯曲速度和弯曲偏转程度随外加电场的增加而增大;NaCl溶液离子强度对凝胶弯曲行为产生影响,当溶液离子强度I≤0.05时,凝胶向电场负极弯曲,当溶液离子强度I≥0.05时凝胶向电场正极弯曲;在循环电场作用下,其弯曲响应行为具有良好的可逆性。     

壳聚糖水凝胶的制备及其在药物释放中的应用

水凝胶作为性能良好的载体,在药物的控释、组织工程等领域有着广泛的应用。壳聚糖是一类天然的带正电荷的碱性多糖,由其形成的水凝胶具有较好的生物相容性、生物降解性、抗菌和低细胞毒性,因此,壳聚糖水凝胶有着良好的生物应用前景。本文综述了壳聚糖水凝胶的制备方法(包括物理交联法和化学交联法),在物理交联法部分着重介绍了离子化合物及聚电解质分子与壳聚糖通过离子交联形成水凝胶,以及利用分子链间的疏水作用形成壳聚糖水凝胶的方法;而在化学交联法部分介绍了合成壳聚糖水凝胶的化学手段,包括交联剂、光照辐射和酶的使用。继而概述了壳聚糖水凝胶在药物缓释应用方面的研究进展,包括温度、pH值和电场响应的药物控释体系。最后展望了壳聚糖水凝胶未来的发展前景。     

壳聚糖基聚合物的生物医学研究进展

综述了在壳聚糖特性，壳聚糖基聚电解质配合物，壳聚糖凝胶和ＰＨ响应壳聚糖基网络聚物等方面的研究进展。     

磺化β-环糊精水凝胶的电刺激响应行为

将β-环糊精用环氧氯丙烷交联制成水凝胶,然后用浓硫酸改性引入-SO3H基团,制备了一种电响应性β-环糊精水凝胶,研究了该凝胶的溶胀性能和电刺激响应行为。结果表明,该凝胶在Na2SO4溶液中其平衡溶胀率随Na2SO4离子强度的增大而减小。在Na2SO4溶液中于非接触直流电场作用下,该凝胶向电场负极弯曲,弯曲速度和应变随外加电压的增大而增大,并随Na2SO4离子强度的增大于0.05处出现最大值。但该水凝胶的电响应行为不受外界溶液pH的影响。在循环电场作用下,其电刺激响应行为具有良好的可逆性。     

海藻酸钙水凝胶对电刺激的响应行为

以CaCl2为交联剂采用浸渍法制备了海藻酸钙水凝胶，研究了海藻酸钙水凝胶的溶胀吸水率及其电刺激响应行为．结果表明，在NaCl水溶液中，海藻酸钙水凝胶的平衡溶胀比随着NaCl溶液浓度的增大而增大，随着交联剂CaCl2溶液浓度的增大而减小．海藻酸钙水凝胶在NaCl水溶液中在非接触直流电场作用下向负极弯曲，其弯曲速度、弯曲偏转程度和应变随着外加电场强度的增大而增大，随着NaCl溶液离子强度的变化在离子强度I=0．03时出现临界最大值，随着交联剂CaCl2溶液浓度的增大而减小．在周期性电场作用下，海藻酸钙水凝胶的弯曲响应行为具有良好的可逆性．     

数字图像相关法在稀土掺杂水凝胶电响应行为测量中的应用

基于放大成像技术、高速摄像技术与数字图像相关方法,研究了稀土掺杂水凝胶在非接触直流电场作用下的电刺激响应行为,并对相关的机理进行了探讨。实验结果表明,在非接触直流电场作用下,掺入稀土后的Sm/Gel/P(AA/AM)、Eu/Gel/P(AA/AM)水凝胶与Gel/P(AA/AM)水凝胶相比,对电场的响应更为敏感;稀土掺杂水凝胶均随着电场的增大,形变位移增大;水凝胶在掺杂稀土后沿着电场方向产生形变,在掺杂稀土前逆着电场方向产生形变。文中测试方法具有实验装置简单、全场非接触、无附加质量、无附加阻尼、测量变形范围可调等优点。数字图像相关方法用于此类材料力学性能的研究是一种行之有效的方法。     

荧光水凝胶传感器及其传感响应机制研究进展

荧光水凝胶是一类具有三维交联网络、荧光发射性能的新型高分子复合材料，能够在外界目标分析物的刺激下发生荧光强度或荧光发射颜色的改变。因此，荧光水凝胶能够作为定量检测目标分析物浓度的重要工具，并且表现出良好的荧光稳定性与检测便携性。近年来，研究人员开发出了多种基于不同类型响应机制的荧光水凝胶传感探针，并应用于各种类型目标分析物的检测。在传统的荧光水凝胶传感器的设计过程中，大多数是基于目标分析物与水凝胶内部的荧光材料间高度的特异性识别功能，这需要目标分析物与荧光材料之间的高度一一对应关系，限制了此类荧光水凝胶传感器的检测广泛性。然而，通过间接性作用构建的荧光水凝胶能够引入一个中间媒介作为桥梁进一步实现各类目标分析物的特异性识别与响应。该种级联响应目标分析物的方式打破了传统荧光水凝胶传感器的局限性。本文根据荧光水凝胶传感体系构建过程中所涉及到的信号响应机制，将荧光水凝胶传感器分为三大类，主要包括直接响应型、竞争性响应型、非竞争性响应型，这对于启发人们构建新型荧光水凝胶传感器具有重要的参考意义。最后，对荧光水凝胶传感器在检测领域所面临的机遇与挑战进行了总结与展望。     

Modelling deformation behaviour of polyelectrolyte gels under chemo‐electro‐mechanical coupling effects

In this paper, the deformation behaviour of polyelectrolyte gels induced by surrounding chemical and electrical stimulations is investigated. The polyelectrolyte gel is composed of a solid polymer‐based network attached with electric charged groups and an interstitial fluid, and it will induce various deformations such as swelling, de‐swelling as well as bending due to the variation of ambient chemical and electrical field. In order to study these mechanical behaviours of the polyelectrolyte gels, a multiphysics mathematical model is developed based on the multiphase mixture theory. In the present equilibrium study, the neglect of electro‐osmosis phenomenon is assumed and the numerical simulations are carried out for a two‐dimensional gel strip with the coupling effect of the external salt solution and electric field. The bending of the gel strip is concluded from the numerical results, which agrees with the previous experimental observation. The influence of several parameters on the deformation behaviour of the gel strip has also been discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

强化自组装技术在多层复合分离膜领域的应用

强化自组装技术是近年来被发展的一种制备聚电解质复合物多层膜的新方法,该法巧妙地利用外加力与聚合物间作用力的协同效应,强化组装过程,简化成膜程序,提高膜分离性能.总结了近年来课题组在这一领域的研究进展.     

Translational motion of a polymer gel microrod via electrically induced wave propagation

The aim of the present study relies on the potential to control the motion of a polymer gel microrod by means of a suitable electric field. It is well known that a polyelectrolyte gel can change its conformation under the effects of an electric field. Inducing a local deformation in a gel rod, it is possible to propagate the deformation along the gel rod itself, shjfting it in the same direction as the electric field. This technique, which can be viewed as a sort of wave propagation method, can be used to perform a controlled translational motion of the whole gel body.A simple device has been designed to provide the desired application of the electric field and to study the gel microstructure response. Experimental measurements characterizing the main electro-kinetic properties of the polymer gel have been carried out, and the related results used in the simulation of the gel motion. Finally, real motion experiments have been performed.Both theoretical and experimental results show that this novel technique can induce and control the translational motion of a polymer gel microrod, but that a high degree of miniaturization of the system is still required to achieve reliability and performance necessary in technological and scientific applications.     

Collagen/hydroxyapatite composite obtained by electric field orientation

The purpose of this study was to obtain and characterize the oriented collagen/hydroxyapatite (COLL/HA) composite materials, using different kind of electric field. The orientation process takes place due to the dipolar collagen structure. The collagen molecules are electrically charged and can become oriented if an electric field is applied. The composites were obtained by the co-precipitation method starting from collagen gel and hydroxyapatite precursor. The mineralized collagen gel was introduced in an electric field for 1 h, frozen and lyophilized. In order to study the orientation process parameters, two types of electric fields were tested: pulsatory and superposed (both direct and pulsatory). The obtained materials were characterized by XRD, FTIR and SEM. Best results in what it concerns the oriented character of the microstructures, as resulted from SEM images, were obtained for a pulsatory field of 0.93 V/cm, the presence of the direct electric field component decreasing the orientation degree. The average orientation degree, calculated at the magnification of 1000× was about 95%.     

BaTiO_3@Cu核-壳复合粒子电/磁双响应性能

以平均粒径约为500nm的BaTiO_3微球为基核,通过"一步法"成功地制备了BaTiO_3@Cu核-壳复合粒子。利用SEM、TEM、XPS、介电测量分析仪和阻抗分析仪等对复合粒子的组成、结构、介电性能和磁性能进行测定。另外将纯BaTiO_3和BaTiO_3@Cu核-壳复合粒子分别分散到水凝胶中,通过测量和分析在有/无电场、磁场和电磁复合场作用下得到的水凝胶的储能模量,考察粒子在水凝胶中的电、磁和电磁响应性能。结果表明,BaTiO_3@Cu复合粒子具有完整清晰的核-壳结构,在整个表面壳层铜元素中,Cu(0)的原子分数达到了90at%,具有优良的介电性能和磁性能。BaTiO_3@Cu核-壳复合粒子是一种对外加电场和磁场作用都具有响应性能的多功能新型智能材料,且其电磁复合响应性能显著强于纯BaTiO_3粒子。     

Kirigami-Design-Enabled Hydrogel Multimorphs with Application as a Multistate Switch

Morphing materials have promising applications in soft robots, intelligent devices, and so forth. Among the various design strategies, kirigami structures are recognized as a powerful tool to obtain sophisticated 3D configurations and unprecedented properties from planar designs on common materials. Here, some kirigami designs are demonstrated for programmable, multistable 3D configurations from composite hydrogel sheets. Via photolithographic polymerization, perforated composite hydrogel sheets are fabricated, in which soft and active hydrogel strips are patterned in stiff and passive hydrogel frames. When immersed in water, the gel strips buckle out of plane due to swelling mismatch. In the kirigami structures, the geometric continuity is disrupted by the introduction of cutouts, and thus the degrees of deformation freedom increases remarkably. Multiple configurations are obtained in a single composite hydrogel by controlling the buckling direction of each strip. Multitier configurations are also obtained by using a hierarchically designed kirigami structure. A multicontact switch of an electric circuit is designed by harnessing the multitier gel configurations. Furthermore, a rotation mode is realized by introducing chirality in the kirigami design. The versatile design of the kirigami structure for programmable deformations should be applicable for other intelligent materials toward promising applications in biomedical devices and flexible electronics.     

Direct Evidence for Structural Transition Promoting Shear Thinning in Cylindrical Colloid Assemblies

In this paper, we describe stimuli‐responsive hydrogels prepared from a rigid rod‐like polyelectrolyte ‘imogolite’ and a dicarboxylic acid. The hydrogel exhibited thixotropy in response to mechanical shock within the order of seconds or sub‐seconds. Here, using the latest structural/rheological characterisation techniques, the relationship between the structural transition processes and the shear thinning was estimated. The evidence obtained by the experiments revealed for the first time the direct relationship between the microscopic structural change and the macroscopic thixotropic behavior that have been extensively discussed. The thixotropic hydrogel has the hierarchical architecture in the combination of imogolite and dicarboxylic acid, i.e., sheathed nanotubes/hydroclusters of cross‐bridged nanotubes/frameworks. The formation and disintegration of the network structure upon resting and agitating, respectively, were the origin of gel/sol transition (thixotropy), although the hydroclusters of cross‐bridged nanotubes were maintained throughout the transition.     

负载二甲酸钾缓释抗菌微球的构建

为避免二甲酸钾(KDF)在酸性环境下分解过快, 调节仔猪肠胃道酸碱性和菌落平衡, 实现KDF靶向释放抗菌, 本研究以可生物降解的壳聚糖(CS)、羧甲基纤维素(CMC)和无机刚性材料P型沸石分子筛(Zeolite P)为载体, 负载抗菌药物二甲酸钾制备控释水凝胶微球。发现CS中-NH₂与CMC中-COOH离子作用, 可形成结构稳定的聚电解质复合物。溶胀率的差异性表明CS/CMC/Zeolite P水凝胶微球对pH高度敏感。加入Zeolite P使水凝胶微球在pH1.2保持原有形貌且不被降解破裂。CS/CMC/Zeolite P/KDF抗菌微球的包封率为47.75%, 载药率为23.88%, 可有效缓释KDF, 在pH7.4磷酸盐缓冲溶液中的缓释性比pH1.2更优。CS/CMC/Zeolite P/KDF抗菌微球浓度为96 mg/mL时对大肠杆菌最大抑菌率为83%, 有效提高了KDF利用率。     

钛酸钡-明胶复合含水弹性胶体电控力学行为

将无机钛酸钡颗粒分散到含水明胶体系中,在有、无电场作用下分别胶凝得到了两种类型的复合弹性水凝胶。通过对胶体的内部颗粒分散情况分析和压缩模量的测试,研究了该胶体体系对电场的响应。结果表明,两种类型的弹性水凝胶分散相颗粒的分布有明显不同,对电场的响应程度也有很大差异。分析认为,电场作用使颗粒有序分布于连续相的胶联网络中,并形成链状结构。颗粒的有序分布使胶体的压缩模量增强,对电场作用的响应程度增大,在钛酸钡质量分数为1.5% 时胶体压缩模量出现一个极大值,并对电场响应最强。