Nitroxide spin probe study of probe size,hydrogen bonding and polymer matrix rigidity effects on poly(acrylic acid)/poly(ethylene oxide) complexes

An electron spin resonance (ESR) spin probe study was performed on 1 : 1 by weight poly(acrylic acid) (PAA)/poly(ethylene oxide) (PEO) complex over the 100–450 K temperature range with a series of tetramethylpiperidyloxy‐based spin probes. Measurements of the parameters T_5mT, Ta and Td demonstrated the effects of probe size and the strength of hydrogen bonding. The probes in the series Tempone, Tempo, Tempol and Tamine (respectively 4‐oxo‐, unsubstituted, 4‐hydroxy‐ and 4‐amino‐2,2,6,6,‐tetramethylpiperidine ‐1‐oxyl) displayed noticeable increases in the hydrogen‐bonding effect, as indicated by Ta and Td. These increases correlated with increasing hydrogen bond acceptor strength. On the other hand, as the probe size became larger, T_5mT gradually increased due to the free volume decrease. These effects were analyzed using the established theoretical relationship of T_5mT to probe volume expressed by f. Meanwhile, in order to investigate the effect of polymer matrix rigidity, a similar study was performed with a nitroxide spin probe, 2,2,6,6‐tetramethyl‐1‐piperidine‐1‐oxyl (Tempo), on PAA/PEO complexes of different weight compositions. The quantitative fast motion fraction in the composite ESR spectrum was calculated. The influence of changes in the composition of PAA on the molecular mobility was characterized by changes of the spectral parameters and τ_c. The molecular mobility was shown to diminish with increasing content of PAA in PAA/PEO blends duo to the restriction of the polymer matrix rigidity increase. Copyright © 2003 John Wiley & Sons, Ltd.     

Perfluoro-1,3,5-tris(p-oligophenyl)benzenes: Amorphous Electron-Transport Materials with High-Glass-Transition Temperature and High Electron Mobility

Perfluoro-1,3,5-tris(p-quaterphenyl)benzene (PF-13Y) and perfluoro-1,3,5-tris(p-quinquephenyl)benzene (PF-16Y) have been synthesized and characterized. They showed higher glass transition temperatures compared with perfluoro-1,3,5-tris(p-terphenyl)benzene (PF-10Y). Organic light-emitting diodes were fabricated using these materials as the electron-transport layers. PF-13Y and -16Y are better electron transporters than PF-10Y. The electron mobilities of PF-10Y and Alq₃ were measured by the time-of-flight technique. PF-10Y showed higher electron mobilities (10⁻⁴ cm²/V s) and weaker electric field dependence compared with Alq₃.     

Effect of electrolyte type on the electrokinetic behavior of sulfonated polystyrene model colloids

Sulfonated polystyrene latex particles were prepared by a two-stage shot-growth emulsion polymerization process in the absence of emulsifier. Sodium styrene sulfonate (NaSS) was used as an ionic co-monomer to produce a series of latex particles with the same particle size but with different surface charge densities. The electrophoretic mobility of this functionalized model colloid was studied in the presence of various types of inorganic electrolytes. The _e curves of these latexes exhibit a pronounced maximum at high electrolyte concentrations: 5·10^–2 M for 11 electrolytes and 10^–2 M for 21 and 12 electrolytes. When a 31 electrolyte (LaCl₃) was used, the electrophoretic mobility changed to positive values at high concentration due to the specific adsorption of lanthanum species. The experimental results for the electrokinetic characterization of these sulfonated polystyrene model colloids suggest that the surface of the particles is covered by a layer of oligomers or polymer chains which shift the shear plane toward the bulk solution, increasing the anomalous surface conductance of the polystyrene microsphere-electrolyte solution interface.     

An Exploration of the Effect of the Kleier Model and Carrier-Mediated Theory to Design Phloem-Mobile Pesticides Based on Researching the N-Alkylated Derivatives of Phenazine-1-Carboxylic Acid-Glycine

The Kleier model and Carrier-mediated theory are effective for molecularly designing pesticides with phloem mobility. However, the single Kleier model or Carrier-mediated theory cannot achieve a reliable explanation of the phloem mobility of all exogenous substances. A detailed investigation of the two models and the scope of their applications can provide a more accurate and highly efficient basis for the guidance of the design and development of phloem-mobile pesticides. In the present paper, a strategy using active ingredient-amino acid conjugates as mode compounds is developed based on Carrier-mediated theory. An N-alkylated amino acid is used to improve the pesticide’s physicochemical properties following the Kleier model, thus allowing the conjugates to fall on the predicted and more accessible transportation region of phloem. Moreover, the influence of this movement on phloem is inspected by the Kleier model and Carrier-mediated theory. To verify this strategy, a series of N-alkylated phenazine-1-carboxylic acid-glycine compounds (PCA-Gly) were designed and synthesized. The results related to the castor bean seeds (R. communis L.) indicated that all the target compounds (4a–4f) had phloem mobility. The capacity for phloem mobility shows that N-alkylated glycine containing small substituents can significantly improve PCA phloem mobility, such as 4c(i-C₃H₇-N) > 4a(CH₃-N) ≈ 4b(C₂H₅-N) > 4d (t-C₄H₉-N) > PCA-Gly > 4e(C₆H₅-N) > 4f(CH₂COOH-N), with an oil–water partition coefficient between 1.2~2.5. In particular, compounds 4a(CH₃-N), 4b(C₂H₅-N), and 4c(i-C₃H₇-N) present better phloem mobility, with the average concentrations in phloem sap of 14.62 μΜ, 13.98 μΜ, and 17.63 μΜ in the first 5 h, which are 8 to 10 times higher than PCA-Gly (1.71 μΜ). The results reveal that the Kleier model and Carrier-mediated theory play a guiding role in the design of phloem-mobile pesticides. However, the single Kleier model or Carrier-mediated theory are not entirely accurate. Still, there is a synergism between Carrier-mediated theory and the Kleier model for promoting the phloem transport of exogenous compounds. Therefore, we suggest the introduction of endogenous plant compounds as a promoiety to improve the phloem mobility of pesticides through Carrier-mediated theory. It is necessary to consider the improvement of physicochemical properties according to the Kleier model, which can contribute to a scientific theory for developing phloem-mobile pesticides.     

基于Riesz势空间分数阶算子的非局部粘弹性力学元件

将幂函数引入Eringen非局部线粘弹性本构,导出Riesz势形式的应力-应变关系.利用该关系,构造非局部弹簧和非局部阻尼器两类元件;利用元件的串联和并联,建立非局部Kelvin和非局部Maxwell粘弹性模型,推导模型的松弛模量和蠕变柔量.进一步,给出非局部粘弹性模型在生物组织超声波耗散建模中的应用.     

非晶InGaZnO薄膜成分配比对透明性和迁移率的影响

利用固相反应法制备了富铟含量在不同成分配比下的高质量InGaZnO陶瓷靶材,采用脉冲激光沉积法,在基片温度为20 ℃、氧压为1 Pa条件下,在石英玻璃衬底上生长了非晶InGaZnO薄膜,并对薄膜进行X射线衍射、透射吸收光谱、拉曼光谱与霍尔效应测试。通过对InGaZnO薄膜的测试表征,在较低温度条件下,铟含量较高的薄膜样品保持了非晶结构、可见光的高透明性和高电子迁移率,InGaZnO薄膜有望应用于电子器件。     

高电子迁移率晶体管微波损伤仿真与实验研究

针对AlGaAs/InGaAs型高电子迁移率晶体管,利用TCAD半导体仿真工具,从器件内部空间电荷密度、电场强度、电流密度和温度分布变化分析出发,研究了从栅极注入1 GHz微波信号时器件内部的损伤过程与机理。研究表明,器件的损伤过程发生在微波信号的正半周,负半周器件处于截止状态;器件内部损伤过程与机理在不同幅值的注入微波信号下是不同的。当注入微波信号幅值较低时,器件内部峰值温度出现在栅极下方靠源极侧栅极与InGaAs沟道间,由于升温时间占整个周期的比例太小,峰值温度很难达到GaAs的熔点;但器件内部雪崩击穿产生的栅极电流比小信号下栅极泄漏电流高4个量级,栅极条在如此大的电流下很容易烧毁熔断。当注入微波信号幅值较高时,在信号正半周的下降阶段,在栅极中间偏漏极下方发生二次击穿,栅极电流出现双峰现象,器件内部峰值温度转移到栅极中间偏漏极下方,峰值温度超过GaAs熔点。利用扫描电子显微镜对微波损伤的高电子迁移率晶体管器件进行表面形貌失效分析,仿真和实验结果符合较好。     

聚(3-己基)噻吩薄膜中电荷传导的研究

对两种具有相同化学结构的聚(3-己基)噻吩膜进行了电荷传导研究以检验膜的结构对载流子迁移率的影响. 一种膜是由3-己基噻吩单体经电化学合成直接制备的膜(原位生长膜); 另一种膜是将原位生长膜溶于三氯甲烷后重新滴涂而成的(滴涂膜). 研究表明, 虽然两种膜的制备方法不一样, 但在最低(0.02%)和较高(20%～30%)掺杂率下两膜中的载流子迁移率相一致; 然而在中等掺杂率区域, 两膜中的载流子迁移率明显不同. 对于原位生长膜, 载流子迁移率在低掺杂区域几乎保持不变, 当掺杂率大于1%后开始上升; 而在滴涂膜中, 随着掺杂率的增加, 迁移率先下降然后迅速升高. 上述两种迁移率变化特征分别与以前研究中观察到的电化学合成高分子膜和化学合成高分子旋涂或滴涂膜中迁移率的变化特征相一致, 表明了迁移率随掺杂率变化特征的改变是由膜的结构变化而引起的     

Stochastic simulation of reactive separations in capillary electrophoresis

A stochastic (Monte Carlo) simulation is used to investigate thermodynamic and kinetic contributions from the reversible A <--> B reaction in capillary electrophoresis (CE). The effects of equilibrium constant, rate constant, and electrophoretic mobility on the molecular zone profiles and the corresponding statistical moments are evaluated. As the reaction approaches steady state, the velocity of the zone is governed by the equilibrium constant and the electrophoretic mobilities of the reacting molecules. When the equilibrium constant is less than unity, the mean zone velocity is more similar to that of the reactant A. Conversely, when the equilibrium constant is greater than unity, the velocity is more similar to that of the product B. The extent of zone-broadening and asymmetry at steady state is dependent upon the equilibrium constant, the characteristic reaction lifetime, and the electrophoretic mobility difference between reacting molecules. If all other parameters are held constant, the plate height is greatest and skew is least when the equilibrium constant is unity. The plate height increases linearly with the characteristic reaction lifetime and electrophoretic mobility difference, whereas the skew is independent of these parameters. These conclusions have important implications for the elucidation of thermodynamic and kinetic information from experimental data.     

Principle of a new immunoassay based on electrophoretic mobility of poly(styrene/alpha-tert-butoxy-omega-vinylbenzyl-polyglycidol) microspheres: application for the determination of helicobacter pylori IgG in blood serum

The principle of a novel latex diagnostic test for the determination of antibodies against Helicobacter pylori in blood sera is described. The test is based on the measurement of the electrophoretic mobility of the microspheres with immobilized H. pylori antigens. The electrophoretic mobility of these microspheres depends on the concentration of the antibodies against H. pylori in suspending medium. Particles with hydrophilic polyglycidol in the surface layer were used for the test. The microspheres were obtained by an emulsifier-free emulsion copolymerization of styrene and alpha-tert-butoxy-omega-vinylbenzyl-polyglycidol macromonomer (D(n) = 220 nm, diameter polydispersity factor D(w)//D(n) = 1.02). Activation of polyglycidol hydroxyl groups with cyanuric chloride allowed for covalent immobilization of H. pylori antigens. The fraction of H. pylori not specifically adsorbed onto the microspheres was negligible. Changes of the electrophoretic mobility of the microspheres with the surface concentration of the covalently immobilized H. pylori antigens Gamma = (1.6 +/- 0.3) . 10(-3) g m(-2) were suitable for the detection of the antibodies in the sera of patients with titer in the range (determined by the indirect ELISA test) from 1:500 to 1:32 000.