低掺杂吡咯低聚物-聚苯乙烯复合膜／电解质溶液体系的介电谱解析——选择渗透性和膜内离子扩散行为

制备了十二烷基苯磺酸掺杂的吡咯低聚物（DBSA-oligopyrrole,DOPY）／聚苯乙烯复合膜,首次在40Hz-4 MHz频率范围测量了该膜在5种电解质中和不同酸度条件下的介电谱,并在等效电路模型和界面极化理论基础上分析了弛豫的特征并确定了弛豫机制,并利用介电参数对各测量结果进行了膜参数的解析,获得了关于该DOPY／PS复合膜对不同电解质的渗透能力和离子导电特征的原位信息,以及介质环境的酸度对电参数的影响：介电参数给出了聚吡咯在聚苯乙烯中的最佳含量：理论解析给出了DOPY／PS复合膜对不同电解质溶液的透过性及选择性规律．结果表明：由于聚吡咯的存在明显提高了纯聚苯乙烯膜的渗透能力,在本研究条件下,确定质量百分数为1％的DOPY／PS复合膜的渗透性能最优;定量计算了膜内大约含有0．80mol／m^3的负电量,预测了复合膜对含有不同阴离子的电解质具有选择透过性;此外,分析了由于膜本身的性质受溶液pH的影响从而造成的透过性随溶液pH变化的原因．此研究首次将介电解析从以往的分离膜体系拓展到了复合型导电聚合物膜体系．     

聚吡咯/聚苯乙烯混合膜/电解质溶液体系的介电谱解析电解质种类和浓度对膜透过性的影响

测量了混入聚吡咯粒子的聚苯乙烯混合膜在不同浓度的氯化钠、氯化钾、氯化钙及氯化镁体系的介电谱, 在40 Hz~11 MHz, 发现了显著的双介电弛豫现象(Double-relaxation phenomena). 基于Maxwell-Wagner理论讨论了弛豫产生的机制, 将体系进行了模型化, 并利用Hanai理论方法对介电谱进行了解析, 从获得的内部参数对混合后的膜荷电性质以及混合膜对离子的透过性进行了详细的讨论, 进而利用Donnan平衡理论推导的膜电位的表达式拟合, 获得了混合膜的固定电荷等参数.     

沸石及核壳结构聚合物粒子分散系的介电解析── 粒子排列模式对体积分数的解释

在40 Hz～110 MHz频率范围对NaA沸石堆积体系和聚苯乙烯-聚吡咯悬浮液进行了介电测量. 两类体系分别在105和107 Hz表现出因界面极化产生的弛豫. 利用Hanai理论解析两类体系的介电谱, 发现解析体积分数与实测体积分数之间存在与体系的浓度相关的明显差异. 通过分析Wagner原始模型阐明了差异的原因, 指出了分散相粒子相互作用力与差异程度间的内在联系, 从介电角度为胶体分散系中粒子统计排列方式的确定提供了判定依据: 当分散系浓度高于临界值时, 其最可取粒子统计排列模式为六方最密型; 低于临界值后, 排列模式随浓度的降低逐渐向简单立方型转变.     

膜/液界面浓度极化现象的介电解析

对由强、弱荷电膜和溶液构成的膜／液非均匀体系，在10－107Hz频率范围进行了介电测量，在直流偏压下，该体系显示了二个显著的介电弛豫．利用具有电导率分布相，即浓度极化相的介电理论对强行电的离子交换膜的结果进行了介电解析，从实验上测得的介电参数求出了反映膜／液界面浓度极化层构造的参数，讨论了该体系产生介电弛像的原因、说明了介电理论的合理性，并提出了膜／液界面体系产生介电弛豫现象的可能机理．     

壳聚糖膜对水杨酸吸附及释放过程的实时介电谱法研究

制备了壳聚糖膜,并且测量了壳聚糖膜/水杨酸溶液、含水杨酸的壳聚糖膜/蒸馏水两个膜/液体系的介电谱,在100～700 kHz频率范围,发现两种体系都存在显著的介电弛豫现象,而且该弛豫的特征参数随壳聚糖膜在相应溶液相中浸泡时间的不同而变化.将该体系介电模型化、并利用在Maxwell-Wagner界面极化理论上建立的公式对介电谱进行解析,得到了体系中两相--壳聚糖膜相和溶液相的介电常数和电导率随时间的变化曲线.通过分析电导变化曲线得知,壳聚糖膜对溶液中的水杨酸有吸附现象,而含有水杨酸的壳聚糖膜在蒸馏水中可以缓慢释放出水杨酸;吸附过程包含的机制有氢键的形成、疏水力和扩散;而水杨酸的脱附过程则包含吸附过程几种机制的逆反应.理论分析和解析结果都验证了介电谱方法对吸附和释放过程实时监测的有效性.     

非导电微球悬浊系的介电谱——弛豫机制的考察和界面信息的解析

研究了不同浓度电解质溶液中聚苯乙烯微球悬浊液的介电谱, 发现在40 Hz～110 MHz频率范围内出现了两个明显的弛豫. 在介电模型基础上对弛豫原因的理论分析结果表明, 千赫兹频域出现的弛豫是由粒子附近双电层中对离子的扩散所致, 兆赫兹附近出现的弛豫源于空间电荷在固/液界面的累积. 应用Hanai方法计算出体系内部的相参数, 获得了微球/溶液界面的电信息, 并给出了合理解释. 理论计算结果验证了模型和方法的适用性. 实验采用透析法调制样品, 有效地防止了体系内部粒子二次团聚的发生.     

反渗透膜UTC-70在水溶液中的介电谱及其解析

根据平面层状体系介电弛豫理论研究了反渗透膜UTC-70在各种浓度氯化钠和氯化钾溶液中的介电弛豫行为.利用计算机拟合的方法得到膜/溶液体系的介电参数,并由此计算得到了UTC-70膜相和水溶液相的相参数,获得了反映反渗透膜UTC-70荷电情况的信息及其与电解质溶液浓度的关系,介电解析的结果解释了介电弛豫的产生机制.     

中相微乳液的介电弛豫谱解析及弛豫机制研究

对由SDS、CTAB、正庚烷、正丁醇和盐水组成的中相微乳体系进行了介电测量,在不同盐度下低频段出现显著的介弛豫现象,它给出了弛豫时间随盐度的变化关系。通过解析介电谱获得了体系内部结构和电性质等信息,几个介电模型和理论公式被用来解释解析的结果。对弛豫时间的计算结果发现,该弛豫是由多种极化机制参与、界面极化为支配的动力学过程。介电解析和模型计算相互验证,结果暗示着体系盐度变化对中相微乳结构变化的影响和可能的转化机制。     

非导电球型粒子悬浮液宽频介电谱——薄双电层理论的计算机模拟

以Shilov等提出的带有紧密层表面电导率的非导电球型粒子悬浮液宽频介电弛豫的薄双电层理论为基础, 从电动力学角度解释了粒子分散系两种典型介电弛豫(高频和低频弛豫)的机制. 在此基础上, 利用Mathcad程序将该理论定量程序化并建立了粒子/水相分散系介电谱参数与体系内部相参数的关系. 进而利用该程序模拟了溶液浓度、Zeta电位以及分散粒子半径等内相参数对两种弛豫的影响, 结合该理论阐述了不同环境下这两种弛豫的变化规律, 从而为今后更好地利用这两种弛豫表征纳米至毫米级球形粒子分散系的各相电及界面性质提供了有价值的参考.     

PS-PBA粒子分散系的介电弛豫谱解析——同、反离子对弛豫的影响及表界面电参数的计算

制备了近纳米级的聚苯乙烯-丙烯酸丁酯(PS-PBA)复合微球粒子,并在40Hz～110×106Hz的宽频范围测量了该粒子分散在9种电解质中时的介电弛豫谱,发现了与PS微球粒子分散系不同的特异介电弛豫:低频弛豫对反离子种类具有敏感性而高频弛豫则与电解质种类几乎无关;根据Shilov-Dukhin模型和M-W-O模型分别分析了高、低频率的弛豫机制,并通过对介电谱的Cole-Cole拟合获得了各体系的介电参数.进一步利用Hanai方法由介电参数计算获得了所有体系的相参数;详细分析了体系的内部参数受PS-PBA微球自身结构以及电解质种类影响的原因;讨论了离子扩散系数对介电参数的影响,从而得出了低、高频的弛豫特征时间分别由同离子的扩散系数和反离子的扩散系数所决定之结论.最后,结合Grosse宽频介电理论计算了粒子表面的以及双电层的主要电参数,并分析了电解质种类差异对这些电参数的影响.     

Morphology,microhardness, and electrical properties of composites based on polypropylene,montmorillonite, and polypyrrole

The morphology, microhardness, and electrical properties of composites consisting of conductive polypyrrole (PPy) dispersed into a nonconductive polypropylene matrix (PP) as pure component or in form of a sodium montmorillonite/PPy (MMT/PPy) composite have been studied. For comparison, also PP/MMT composites were studied. All types of composites were processed by compression molding or by melt mixing followed by compression molding into plates, which were used for characterization. Scanning electron microscopy and transmission electron microscopy was used to examine the morphology of the prepared materials. The investigation of electrical and dielectric properties was done by dielectric relaxation spectroscopy in a wide frequency range and was related to the composite composition and processing method. The analysis of the conductivity as a function of temperature indicated that the charge transfer mechanism could be described by the variable range hopping model in three dimensions. The microhardness of PP/MMT/PPy composites with different content of MMT or PPy was determined and the creep rate has been estimated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 407–423, 2009     

Dielectric Relaxation Phenomena and Electric Properties of Conductive Composite Polyurethane/Polyaniline Films

Summary: Composite polyurethane/polyaniline (PU/PANI) films have been chemically prepared by oxidative in-situ polymerization of aniline inside the previously swelled PU film. Swelling kinetic studies have shown that for PU films the swelling degree of aniline is 25 wt.%. The dielectric and electrical properties of the composite films were measured using dielectric relaxation spectroscopy and four-probe method. Dielectric measurements as a function of temperature and frequency revealed the presence of a relaxation process for the composite PU/PANI-HCl film. This relaxation was explained in terms of interfacial polarization due to the double-layered structure of the composite film. The activation energy values found by dielectric and electrical measurements are close and this result confirms the conducting character of the PANI containing layer.     

Evidence for a tilted smectic phase in Anopore membranes by dielectric spectroscopy

Collective relaxation processes are completely undetectable in a ferroelectric liquid crystal confined in porous Anopore membranes, as a result of perfect orientation of the smectic layers perpendicular both to the long axis of the pores and the direction of the measuring electric field. In the ferroelectric liquid crystal - Anopore composite only one relaxation process, assigned to rotation of the molecule around the molecular short axis, appears throughout all smectic phases. The temperature dependence of the relaxation frequency and of the dielectric strength of this process also shows no irregularity at the point of polarization sign reversal. The temperature dependence of the relaxation frequency follows the Arrhenius law with an activation energy slightly higher in the ferroelectric SmC* phase. Analysis of the non-linear changes of temperature dependence of the dielectric strength at the SmA-SmC* phase transition enables one to obtain the temperature dependence of the tilt angle of the molecules in the SmC* phase in the Anopore membrane. Dielectric measurements confirm the existence of the tilted smectic phase in Anopore cylindrical channels with no tilt anomaly at the point of polarization sign reversal.     

Evidence for a tilted smectic phase in Anopore membranes by dielectric spectroscopy

Collective relaxation processes are completely undetectable in a ferroelectric liquid crystal confined in porous Anopore membranes, as a result of perfect orientation of the smectic layers perpendicular both to the long axis of the pores and the direction of the measuring electric field. In the ferroelectric liquid crystal – Anopore composite only one relaxation process, assigned to rotation of the molecule around the molecular short axis, appears throughout all smectic phases. The temperature dependence of the relaxation frequency and of the dielectric strength of this process also shows no irregularity at the point of polarization sign reversal. The temperature dependence of the relaxation frequency follows the Arrhenius law with an activation energy slightly higher in the ferroelectric SmC* phase. Analysis of the non‐linear changes of temperature dependence of the dielectric strength at the SmA–SmC* phase transition enables one to obtain the temperature dependence of the tilt angle of the molecules in the SmC* phase in the Anopore membrane. Dielectric measurements confirm the existence of the tilted smectic phase in Anopore cylindrical channels with no tilt anomaly at the point of polarization sign reversal.     

Dielectric characterization of a nanofiltration membrane in electrolyte solutions: its double-layer structure and ion permeation

Dielectric spectroscopy (DS) was applied to a nanofiltration (NF) membrane to detect its double-layer structure and ion permeation. Dielectric measurements were carried out on the systems composed of the NF membrane NTR7450 and dilute solutions of eight electrolytes, LiCl, NaCl, KCl, NH(4)Cl, MgCl(2), CaCl(2), BaCl(2), and CuCl(2). Two relaxations were observed in the frequency range from 40 Hz to 4 MHz for each system. On the basis of characteristics of the dielectric spectra and the Maxwell-Wagner interfacial polarization theory, the low-frequency relaxation was attributed to inhomogeneity of the membrane structure itself, whereas the high-frequency relaxation was attributed to interfacial polarization between the membrane and the solution. A multiphase dielectric model previously developed by one of the authors and co-workers was adopted to present systems to analyze the dielectric spectra, and electric parameters, i.e., capacitance and conductance, of the two layers composing the membrane were obtained. The electric properties estimated for the two layers were different and changed with the environment in a different manner. Further analyses suggest that the two layers had a different separation mechanism due to their difference in materials, looseness, and fixed charge content. The fixed charge density of one layer was estimated, and the ion permeation difficulties in both layers was compared. This research revealed that DS was by far an effective method to obtain detailed electric parameters about the inner multilayer structure of the NF membrane and to elucidate separation mechanisms of each layer.     

浓差极化的介电模型——复合膜/溶液体系的数值模拟

提出了具有电导率和介电常数线性分布的介质的介电模型, 并导出了其内部电的和结构性质的参数与宏观测量的电容和电导之间定量关系的理论表达式, 以模拟复合膜中的多孔层部分的介电弛豫行为. 大量的模拟计算描述并解释了多孔层介电谱随介电常数分布、厚度等性质而变化的规律. 进一步对具有层状构造的复合膜以及复合膜和溶液相组成的多层体系的弛豫行为进行了数值模拟, 比较了三个体系(多孔层、复合膜、复合膜/液相层状体系)的介电谱, 结果揭示了介电谱对各层性质的依赖关系. 所提出的电导率和介电常数线性分布的多孔层的介电模型, 也可用于具有其他电导率、介电常数分布规律的体系.