Transport properties in polypyrrole powders and in PPy–PVA composites: Evidence for bipolaronic clusters

Experimental results on electrical conductivity of both doped polypyrrole (PPy) powder and conducting poly(vinyl alcohol) (PVA)–PPy composite are presented. In each case, FeCl₃ has been used as the oxidizing–polymerizing agent. Results are interpreted on the basis of a model in which counter-ions act through their attractive potential by forming conducting ways between chains and allowing transverse conduction. In the case of PPy powder, the major contribution to conduction mechanisms is hopping between polaronic clusters. In the case of the composite, an additional contribution results from fluctuation-induced tunneling through thin insulating PVA barriers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:709–713, 1998     

原位红外光谱法研究PTT的结晶与构象关系

通过分析PTT的红外光谱随温度变化的情况,研究了PTT在等速升温过程中的结晶行为和分子链 构象的转变。发现随着温度上升,显示结晶的谱带略有增强,分子链中丙二醇单元的构象发生了转变:中间 的两个碳碳键由反式构象向旁式构象转变,同时两边的两个碳氧键由旁式构象转变为反式构象。     

化工传递过程基础教学方法的探讨与研究

化工传递过程基础课程在化工类高校人才培养中具有重要的地位,通过对化工传递过程教学经验的总结,提出对比归纳法,自学讨论与精讲相结合教学法,多媒体及仿真技术在化工传递教学中的应用,开卷考核方式,从而达到增强学生学习兴趣、提高教学质量、提升学生实践创新综合能力的目的。     

Modeling of a membrane reactor system for crude palm oil transesterification. Part II: Transport phenomena

The mechanistic modeling of biodiesel production process in membrane reactor with the consideration of chemical reaction, phase equilibrium, and ultrafiltration is important for the membrane reactor design. In part II of this work, the chemical and phase equilibrium (CPE) model for crude palm oil transesterification reaction in the membrane reactor developed in part I is extended to an integration of CPE with modified Maxwell–Stefan model, which considers multicomponent mass transport phenomena of concentration polarization and intramembrane. A good fit of simulated permeate fluxes and apparent solute rejection to the experimental data shows that the model has a good prediction capability. Reversible fouling was found to be the major fouling and no pore plugging was observed. Simulation results verified that micelles were retained by the membrane at CPO:MEOH molar ratio of 1:24 and catalyst concentration of 0.5 wt %. However, phase inversion happened when catalyst concentration of 0.05 and 0.1 wt % were used. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1981–1996, 2015     

2-thiobarbituric acid test for lipid oxidation in food: Synthesis and spectroscopic study of 2-thiobarbituric acid-malonaldehyde adduct

Synthesis, purification, elemental analysis, and spectroscopic studies were undertaken to characterize the structure of the red adduct 2:1 thiobarbituric acid (TBA)-malonaldehyde involved in the evaluation of oxidative rancidity in fats and oils. Thin-layer chromatography, infrared and ultravioletvisible absorption, ¹H (¹H NMR) and ¹³C nuclear magnetic resonance (NMR) spectra were used. A yield of 93% was obtained in the synthesis. The results of elemental analysis agree with the formula for the chloro-monohydrated form, C₁₁H₁₁N₄O₅S₂Cl. Three characteristic absorption maxima at 532, 310, and 245 nm, respectively, were shown in acid aqueous medium (pH 2.9). The characteristic vibrations assigned to the -NH, -OH, C^αH (exocyclic) and -C=S groups were confirmed in the infrared spectra. There was no evidence of thioenolization. ¹H NMR data at δ 5.10 (-CONH- group, H₂O and HCl molecules); δ 11.54 (-OH group of keto-enol tautomer, -NH group); and δ 176.4 (-CONH- group) also were observed. The experimental results obtained were consistent with the existence of two spectral equivalent tautomeric structures. The colored adduct was compared with other TBA-aldehyde compounds.     

Experimental study on the reaction rate of a second‐order chemical reaction in a planar liquid jet

Instantaneous concentrations of reactive species are simultaneously measured in a planar liquid jet with a second‐order chemical reaction to investigate the statistical properties of the chemical reaction rate and the validity of models which have been proposed for concentration correlation. The jet flow contains the reactant A, and the ambient flow contains the reactant B. The results show that the concentration correlation of the reactants makes a negative contribution to the mean reaction rate, and this contribution is important in the downstream direction. The concentration correlation changes owing to the chemical reaction. The effects of the chemical reaction on the concentration correlation change with the flow location and the Damköhler number. The concentration correlation predicted by the Toor's model and the three‐environment model are compared with the experimental results. The results show that these models fail to accurately estimate the concentration correlation. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3969–3988, 2014     

Transport properties study of supplementary cementitious materials: case of tuff,limestone filler and granodiorite

The aim of this research is to determine the effects of replacing cement with tuffs on the transport properties and service life of cement-based materials. Specimens were prepared replacing 5% and 15% by weight of cement with both white and brown tuffs. Additional specimens were prepared replacing cement with 5% and 15% limestone filler and granodiorite to compare the effects of these types of materials. For these four types of specimen as well as a control mortar with no cement replacement transport properties (gas permeability and chloride ingress) were measured as well as porosity and pore diameter. The transport properties were compared the changes in these porosity and pore diameter. Based on the results, white tuff significantly improves the transport properties of the mortars due to its pozzolanic reaction and that white tuff may be an economically and functionally viable replacement for cement where concrete durability is important. Pore diameter and porosity did not correlate well with transport properties.     

Toward a Spatiotemporal Model of Oxidation in Lipid Dispersions: A Hypothesis‐Driven Review

Unsaturated lipids are prone to get oxidized through a sequence of reactions known as lipid oxidation. From a phenomenon considered at the beginning as a mere chemical process and described by the triptych of initiation, propagation, and termination, the vision of lipid oxidation has progressively evolved to further integrate the physical dimension of the phenomenon. Despite tremendous research efforts, however, this sequence of reactions is not yet well understood, especially in lipid dispersions where many facts are still inexplicable and unpredictable under the current paradigm. Here, the aim is to suggest that the main reason why a better understanding has not already been achieved is that the reactional network is not yet organized in a coherent spatiotemporal framework. The novel concepts and hypotheses proposed in this article may help redirecting a significant part of research efforts toward the establishment of a spatially and temporally resolved model of oxidation in dispersed lipids. Practical Application : Predicting how oxidation spreads in lipid dispersions represents a goal of crucial importance for academia but also for industry. Such prediction models would indeed greatly help food manufacturers prevent oxidation by using the most adapted antioxidative strategies for their specific products. To achieve such an objective, it is proposed that the first thing to do is to go beyond the extremely reductive and narrow framework in which this chemical process has been locked in. Indeed, while lipid dispersions are composed of a multitude of lipid colloids, researchers usually consider oxidation at the sole level of an individual droplet or membrane. Instead, lipid oxidation is advocated as a dynamic trafficking of chemical species within large communities of different colloidal objects such as droplets, membranes, or micelles dispersed in water—a system that dubbed “colloidal ecosystem”. This might represent a scale complementary to the scales of individual colloids or molecules that were the sole consideration so far to try to represent lipid oxidation. Only then can one hope to effectively apply modeling and “omics” approaches, as is explained in more details in this article.     

Janus石墨烯量子点在生物膜中的输运行为：分子动力学模拟

作为纳米载体,石墨烯量子点已广泛应用于生物医药领域,然而对于异质结构的石墨烯量子点细胞膜内化路径研究不足。从空间异质性结构设计出发,构建了一系列不同氧化程度与空间异质分布的Janus石墨烯量子点。基于分子动力学模拟研究了不同结构的Janus石墨烯量子点跨膜输运行为,通过分析跨膜输运过程中的构型变化、分子间作用能量、溶剂可及面积等参数,发现Janus石墨烯量子点跨膜输运行为由亲水-亲油平衡、空间异质分布控制,且呈现外力牵引依赖性变化。本文在分子水平上系统研究了Janus石墨烯量子点与细胞膜相互作用规律,对其结构设计及生物医药应用提供理论指导。     

Janus石墨烯量子点在生物膜中的输运行为：分子动力学模拟

作为纳米载体,石墨烯量子点已广泛应用于生物医药领域,然而对于异质结构的石墨烯量子点细胞膜内化路径研究不足。从空间异质性结构设计出发,构建了一系列不同氧化程度与空间异质分布的Janus石墨烯量子点。基于分子动力学模拟研究了不同结构的Janus石墨烯量子点跨膜输运行为,通过分析跨膜输运过程中的构型变化、分子间作用能量、溶剂可及面积等参数,发现Janus石墨烯量子点跨膜输运行为由亲水-亲油平衡、空间异质分布控制,且呈现外力牵引依赖性变化。本文在分子水平上系统研究了Janus石墨烯量子点与细胞膜相互作用规律,对其结构设计及生物医药应用提供理论指导。     

环管反应器中聚丙烯颗粒内部的质量与热量传递模型

针对环管反应器中Ziegler-Natta催化剂催化的聚丙烯颗粒增长过程,采用多层模型建立了聚丙烯颗粒内部的质量与热量传递预测模型.通过模型模拟得到聚丙烯颗粒内部的丙烯单体浓度梯度和温度梯度.此外,通过模型分析了聚丙烯颗粒的增长规律.结果表明,环管反应器中的聚丙烯颗粒内部的单体浓度梯度明显,该浓度梯度值随扩散系数的增大而减小,随催化剂初始粒径减小而减小;相比于浓度梯度而言,聚丙烯颗粒内部的温度梯度并不明显,温度值随聚合进行而增加,温度梯度则随催化剂初始粒径的增加而增加;不同大小的催化剂颗粒增长得到的聚丙烯颗粒的增长倍数不同.     

Comparison of experimental results and numerical predictions of drop diameter from a single submerged nozzle in a liquid‐liquid system

This paper presents a comparison of experimental results and numerical predictions of drop formation from a single submerged nozzle for a liquid‐liquid system. The theoretical model is a modification of previous models used for a two‐stage drop formation mechanism. The model has been tested against experimental data for kerosene drop formation in distilled water using a range of different nozzle diameters. In addition, our liquid‐liquid model has been compared with both experimental and predicted results from published literature. These comparisons demonstrate that for liquid‐liquid systems, the present predictions of drop diameter versus dispersed phase nozzle velocity are in overall agreement with both the present and previous experimental results. In addition, the present model predictions are more accurate than those of previous models for liquid‐liquid systems.     

Synthesis,structural and spectroscopic studies of 1-(2-FUROYL)-3-phenylthiourea: a theoretical and experimental approach

The thiourea derivative 1-(2-Furoyl)-3-phenylthiourea (FPT) was synthesized and characterized by using spectroscopic (IR, Raman, UV–VIS, ¹H and ¹³C NMR) and structural methods (powder X-ray diffraction data). The experimental measurements were complemented with quantum chemical calculations. FPT crystallizes in the monoclinic crystal system, space group P21/c, with cell parameters a?=?4.7679(5) Å, b?=?20.9704(2) Å, c?=?12.5109(5) Å and β?=?109.811(10)°, V?=?1176.87(3) ų. In the crystal structure, the thiourea group makes dihedral angle of 43.8(5)° with the furoyl group, whereas the benzene ring is inclined by 24.3(4)°. The anti-syn geometry of the thiourea unit is stabilized by intramolecular N–H^?…?O hydrogen bond between the H atom of the syn thioamide and the carbonyl O atom. In the crystal structure, molecules of FPT are packed through N–H···S, C–H···O and C–H···C hydrogen bonds, and a π–π interaction with offset arrangement. Hirshfeld surface analysis was performed in order to evaluate and quantify intermolecular interactions. The Hirshfeld surface analysis indicated that the H···H interactions comprise the majority of interactions. Shape index and curvedness clearly indicate π–π interactions in the compound FPT.     

Influence of previous annealing on first stage of degradation of blends of low‐density polyethylene and Mater‐Bi AF05H aged in soil: Comparative thermal analysis study

Samples of low‐density polyethylene (LDPE) filled with a commercial biodegradable material (Mater‐Bi AF05H) were subjected to an accelerated soil burial test in a culture oven. In addition, another series of these blends was subjected to thermal treatment and afterward buried in soil under the same conditions. Comparative studies of the changes in the thermal stability and the structural and morphological properties of the samples were carried out by means of differential scanning calorimetry, dynamic mechanical thermal analysis, and thermogravimetric analysis. The morphological properties under study were the melting temperature, the crystalline content, and the lamellar thickness distribution. The α_I relaxation zone of the mechanical spectra was characterized in terms of tan δ, whereas the α_II and relaxation zones were characterized in terms of E″ according to the Fuoss–Kirkwood equation and with the help of a deconvolution method. Finally, the kinetics of each thermodegradation process was studied using the Broido integral method. The Mater‐Bi hindered the uniform growth of crystallites in PE and facilitate molecular motions, but the thermal treatment seemed to rearrange the crystallites in the crystalline phase of PE and promote segregation of the crystallite sizes. These molecular reorganizations affected the degradation process so that the degradation of the polymeric matrix seemed to be obstructed by the annealing during the first 120 days of aging in soil and only the Mater‐Bi degradation could be observed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3359–3373, 2003     

Transport of organic penetrants through films of cellulose esters in transient regimes: a non-equilibrium thermodynamics analysis

Transport equations are derived in the framework of the rational thermodynamics approach for membrane processes involving a dense (active) polymer layer. The influence of the deformation of the polymer matrix, formation of interacting species, changes in polymer configuration, etc., due to mixing of the penetrant and the polymer can be accounted for in the equations. Studies of permeation fluxes in the transient regime in which the membrane is suddenly put into contact with a solvent can give useful information on the behaviour of polymer-penetrant systems. Experimental results obtained for the transient permeation of alcohols and heptane through different cellulose ester membranes are reported and discussed in the framework of this approach.     

Synthesis and characterization of liquid crystalline polymers containing aromatic ester mesogen and a nonmesogenic ferrocene unit in the spacer

A new series of liquid crystalline polymers containing aromatic triad ester mesogen and 1,1′‐disubstituted ferrocene as a nonmesogenic unit along with polymethylene spacer was synthesized. The polymer was synthesized by a room temperature polycondensation reaction between bis(4‐chloroformyl phenyloxy alkyl ferrocene dicarboxylate) and quinol. The alkyl groups have been varied by an even number of methylene groups with a range from two to ten groups. All the polymers were found to possess liquid crystalline properties. The identification of the mesophase is more transparent with an increase in the spacer. The thermal characteristics were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results reveal that the thermal stability of the polymers was decreased with increasing spacer length. The T_g, T_m, and T_i of the polymers decreased with increasing methylene groups. The incorporation of the ferrocene moiety also has a considerable effect on the glass transition temperature. The char yield of the polymer decreases with an increasing methylene chain length. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3494–3501, 2002