微量量热法研究阴离子表面活性剂在DMA/长链醇体系中CMC和热力学函数

在N,N-二甲基乙酰胺(DMA)/长链醇非水溶液体系中, 利用微量量热仪, 研究阴离子表面活性剂十二烷基羧酸钠(SLA)、十二烷基硫酸钠(SDS)的临界胶束浓度(CMC)和热力学函数. 本文在十二烷基羧酸钠, 十二烷基硫酸钠的N,N-二甲基乙酰胺溶液中, 分别加入长链醇(庚醇、辛醇、壬醇、癸醇), 测定体系的热功率-时间曲线. 借助热力学理论, 由测得曲线, 进一步得到临界胶束浓度和热力学函数(ΔH_m⁰, ΔG_m⁰和ΔS_m⁰). 讨论了温度、醇的碳原子数目、醇的浓度与热力学参数之间的关系. 结果表明, 对十二烷基羧酸钠或十二烷基硫酸钠的DMA溶液, 在含有相同浓度的各种醇的体系中, CMC, ΔH_m⁰和ΔS_m⁰的值随着温度的升高而增加, 而ΔG_m⁰的值随着温度的升高而降低. 在相同温度及相同浓度的醇体系中, CMC, ΔH_m⁰,ΔG_m⁰和ΔS_m⁰的值都随着醇中碳原子数目的增加而降低. 在相同温度及相同醇的体系中, CMC, ΔG_m⁰的值随着醇的浓度的增加而增大, 而ΔH_m⁰, ΔS_m⁰的值随着醇的浓度的增加而减少.     

十六烷基三甲基溴化铵在N,N二甲基乙酰胺/长链醇体系中临界胶束浓度和热力学函数的微量量热法研究

用微量量热法测定了阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)在非水溶剂N,N二甲基乙酰胺(DMA)中,分别加入长链醇(正庚醇、正辛醇、正壬醇、正癸醇)体系的热功率一时间曲线,由测得的曲线上的数据得到了临界胶束浓度(CMC)和形成热(ΔHθm).根据热力学理论,计算了热力学函数(ΔGθm,ΔSθm),讨论了温度、醇中的碳原子数、醇的浓度与临界胶束浓度(CMC)和热力学函数之间的关系.结果表明:十六烷基三甲基溴化铵(CTAB)的DMA溶液,在含有相同浓度的各种醇的体系中,CMC,ΔHθm和ΔSθm的值随着温度的升高而增加;而ΔGθm的值随着温度的升高而略有降低.在相同温度及相同浓度的醇体系中,CMC,ΔHθm,ΔGθm和ΔSθm的值都随着醇中碳原子数的增加而降低.在相同温度及相同醇的体系中,CMC和ΔGθm的值随着醇的浓度的增加而增加;而ΔHθm和ΔSθm的值随着醇的浓度的增加而减少.     

丁二酸二异辛酯磺酸钠在长链醇/N,N-二甲基甲酰胺体系中临界胶束浓度和热力学函数的微量量热法研究

用微量量热法研究了丁二酸二异辛酯磺酸钠(AOT)在N,N-二甲基甲酰胺(DMF)/长链醇(正戊醇、正己醇、正庚醇、正辛醇)体系中的临界胶束浓度(CMC)和热力学函数( , 和 ). 并分析讨论了醇的浓度、醇中的碳原子数及温度与CMC及热力学参数之间的关系. 结果表明, 在AOT/长链醇/DMF体系中, 当醇中的碳原子数相同且醇的浓度相同时, CMC, , 随温度的升高而增大, 而 随温度的升高而降低|当温度相同且醇中的碳原子数相同时, CMC, , 和 随醇浓度的增加都降低|而当温度相同且醇的浓度相同时, CMC, , 和 随醇中碳原子数的增加都降低.     

聚氧乙烯月桂醚在含醇的非水体系中的热力学性质的微量量热法研究

对于非离子表面活性剂聚氧乙烯月桂醚(Brij-35)/N,N-二甲基甲酰胺(DMF)/长链醇(庚醇,辛醇,壬醇,癸醇)体系,利用滴定微量量热仪测定了胶束形成过程的热功率-时间曲线.根据热力学理论,测定了临界胶束浓度和胶束形成热(ΔHmθ),计算了热力学函数(ΔGmθ和ΔSmθ).讨论了温度、醇中的碳原子数、醇的浓度与临界胶束浓度和热力学函数之间的关系.结果表明:聚氧乙烯月桂醚(Brij-35)/DMF/长链醇体系:(1)在含有相同浓度的各种醇的体系中,ΔHmθ和ΔSmθ的值随着温度的升高而增大;CMC,ΔGmθ的值随着温度的升高而降低;(2)在相同温度及相同浓度的醇体系中,CMC,ΔHmθ,ΔGmθ和ΔSmθ的值都随着醇中碳原子数的增加而降低;(3)在相同温度及相同醇的体系中,CMC,ΔHmθ,ΔSmθ和ΔGmθ的值随着醇的浓度的增加都减小.     

Aggregation behavior and catalytic activity of systems based on calix[4]resorcinarene derivatives and surfactants. 1. Mixed micellization of aminomethylated calix[4]resorcinarenes with cetyltrimethylammonium bromide in aqueous dimethylformamide

Mixed micellization of amphiphilic aminomethylated calix[4]resorcinarenes and phenols, which are their structural units, with the cationic surfactant cetyltrimethylammonium bromide (CTAB) in aqueous 10—70 vol % DMF decreases the critical micelle concentration; the resulting aggregates are larger than those in the CTAB—DMF—water systems. The micellization of CTAB with aminomethylated calix[4]resorcinarenes proceeds in two steps, while its micellization with phenols is a single-step process. The micellization characteristics depend on the structure and hydrophobicity of the amphiphilic compound and the concentration of DMF.     

Modeling of thermodynamic behavior of PVT properties and cloud point temperatures of polymer blends and polymer blend + carbon dioxide systems using non-cubic equations of state

In recent years, many factors influencing phase behavior of polymer blends have been studied because of their widely technological importance, as a simple method of formulating new materials with tailored properties which make them suitable for a variety of applications. This work has three main goals which were reached by using the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) and the Sanchez–Lacombe (SL) non-cubic equations of state (EoS), which in previous works have shown their ability to handle long chain and associating interactions. First, both equations of state were tested with the correlation of the specific volumes of pure blends (PBD/PS, PPO/PS, PVME/PS, PEO/PES) and the prediction of the specific volumes for blends; second, the modeling of blend miscibilities in the liquid–liquid equilibria (LLE) of PBD/PS, PPG/PEGE, PVME/PS, PEO/PES, and PnPMA/PS blends; third, the modeling of the phase behavior of PS/PVME blends at various compositions in the presence of CO₂. PC-SAFT and SL pure-component parameters were regressed by fitting pure-component data of real substances (liquid pressure–volume–temperature, PVT, data for polymers and vapor pressure and saturated liquid molar volume for CO₂) and the fluid phase behavior of blend systems were simulated fitting one binary interaction parameter (k_ij) by regression of experimental data using the modified likelihood maximum method. Results were compared with experimental data obtained from literature and an excellent agreement was obtained with both EoS, which were also capable of predicting the fluid phase behavior corresponding to the critical solution temperatures (LCST: lower critical solution temperature, UCST: upper critical solution temperature) of blends.     

Comparative study on interaction of bovine serum albumin with dissymmetric and symmetric gemini surfactant by spectral method

The interaction between bovine serum albumin (BSA) with N, N′-bis(dimethylalkyl) ethylammonium dibromide (C₁₂C₂C_m, m = 8, 12) was investigated by spectral methods. It can be seen that C₁₂C₂C₈ and C₁₂C₂C₁₂ mainly interact with tryptophan residues of BSA from synchronous fluorescence spectra. Fluorescence, far-UV, and near-UV circular dichrosim spectra of BSA are changed by addition of dissymmetric and symmetric gemini surfactant. For surfactant solution, the polarity of the microenvironment surrounding pyrene is lower while the fluorescence lifetime of it is longer and the microviscosity is higher in the presence of BSA than those in the absence of BSA. But compared with C₁₂C₂C₁₂, C₁₂C₂C₈ has lower binding ability with BSA due to the shorter hydrophobic tail and lower symmetry.     

Determination of Optimal Reaction Conditions and Influence of Metal Ions on Cellulose Degradation by Cellulase in the Dioctyl Sulfosuccinate Sodium Salt (AOT)/n-Hexanol/Cyclohexane Reversed Micelle System

The power-time curves of the cellulose degradation by cellulase were determined under the different conditions with the existence of metal ions or not in the dioctyl sulfosuccinate sodium salt (AOT)/n-hexanol/cyclohexane reverse micelle system by the microcalorimeter method. From these curves, the Michaelis constant and the maximum reaction rate of this reaction were obtained. The optimum T, pH and W_o were determined as W_o = 3.011, pH = 5.015, and T = 315.43 K. Under these optimum reaction conditions, the power-time curves of the cellulose degradation by the cellulase with the metal ions were also obtained. The apparent Michaelis constant and the maximum reaction velocity were gained. The relationship between the apparent Michaelis constant and the concentration of the metal ions was established, and the influence of metal ions was discussed as well. The results indicate that some metal ions have promotion roles on the reaction. However, others could inhibit the reaction. These results are significant for the theoretical and application in the field of reverse micelles enzyme catalysis system.     

FTIR study on molecular structure of poly(N-isopropylacrylamide) in mixed solvent of methanol and water

The intrachain and interchain hydrogen bonding of poly(N-isopropylacrylamide) (PNIPA) and intermolecular hydrogen bonding between PNIPA chains and the solvent molecules in the mixed solvent of methanol and water have been quantitatively investigated by using Fourier transform infrared (FTIR) spectroscopy at 25 °C. In this spectroscopic system with curve fitting program, we found that in the C-H stretching region, both the N-isopropyl group and the backbone underwent conformational change upon the solvent composition. An analysis of the amide I band suggested that the amide groups of PNIPA were mainly involved in intermolecular hydrogen bonding with water molecules, and the polymer chains were flexible and disordered in the mixed solvent when the methanol volume fraction (χ_v) was lower than 15%. While χ_v was in the range of 15-65%, about 30% of these intermolecular hydrogen bonding between the polymer and water were replaced by intrachain and interchain hydrogen bonding, consequently, PNIPA shrinked as aggregates. If χ_v was above 65%, the interchain hydrogen bonding became predominant due to the solubility characteristics of amphiphilic methanol, and the PNIPA system was homogeneous solution again. We believe that the reentrant transition is related to the weaker interaction between PNIPA molecules and methanol-water complexes, (H₂O)_m(CH₃OH)_n (m/n = 5/1, 5/2, 5/3, 5/4, 5/5) as compared to that between PNIPA and free water or free methanol.     

Determination of aspartate and glutamate in rabbit retina using polymer monolith microextraction coupled to high-performance liquid chromatography with fluorescence detection

A simple, sensitive and low-cost method was developed for the determination of aspartate (Asp) and glutamate (Glu) in rabbit retina. Polymer monolith microextraction (PMME) using a poly(acrylamide–vinylpyridine–N,N′-methylene bisacrylamide) (AA–VP–Bis) monolithic column was combined with derivatization of Asp and Glu using 8-phenyl-(4-oxy-acetic acid N-hydroxysuccinimide ester)-4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (TMPAB-OSu), and this was used to analyze the derivatives of Asp and Glu by high-performance liquid chromatography (HPLC) with fluorescence detection. The conditions for the derivatization and the subsequent extraction of Asp and Glu derivatives were optimized. The enrichment factors for the derivatives of Asp and Glu were found to be 14.1 and 14.7, respectively, by PMME. The limits of detection of Asp and Glu were 0.14 and 0.53 nmol/L, respectively. The precision and recovery were evaluated with spiked retina. The inter- and intraday relative standard deviations were less than 10%. The proposed method was successfully applied to the determination of Asp and Glu levels in rabbit retina samples with different stages of intraocular hypertension.     

Recent developments in manufacturing emulsions and particulate products using membranes

Membrane emulsification (ME) is a relatively new technique for the highly controlled production of particulates. This review focuses on the recent developments in this area, ranging from the production of simple oil-in-water (O/W) or water-in-oil (W/O) emulsions to multiple emulsions of different types, solid-in-oil-in-water (S/O/W) dispersions, coherent solids (silica particles, solid lipid microspheres, solder metal powder) and structured solids (solid lipid microcarriers, gel microbeads, polymeric microspheres, core-shell microcapsules and hollow polymeric microparticles). Other emerging technologies that extend the capabilities into different membrane materials and operation methods (such as rotating membranes, repeated membrane extrusion of coarsely pre-emulsified feeds) are introduced. The results of experimental work carried out by cited researchers in the field together with those of the current authors are presented in a tabular form in a rigorous and systematic manner. These demonstrate a wide range of products that can be manufactured using different membrane approaches. Opportunities for creation of new and novel entities are highlighted for low throughput applications (medical diagnostics, healthcare) and for large-scale productions (consumer and personal products).     

Application of thermodynamics in a specific force field to the adsorption of Al ions on the chelating resins Ostsorb Oxin, Ostsorb Salicyl, Spheron Oxin, and Spheron Salicyl: Mathematical analysis of sorption isotherms using nonlinear mean square software

The sorption mechanism of Al³⁺ on chelating resins by means of mathematical analysis of sorption isotherms using nonlinear mean square software was studied. This method should yield more detailed information than classical thermodynamics and should be more flexible than the statistical-mechanical method, so that it would make it possible to obtain fairly easily relations directly applicable in practice. This model defined the specific potential Φ_Al^R for the ion in a resin (which depends on properties of resin and ion). On the basis of this model, N and PO isotherms were derived. To study the sorption mechanism, the Freundlich, Langmuir, N and PO equations (models) of isotherms were used. It was estimated that the functional groups (8-hydroxyquinoline and salicylate) in the studied chelating resins influence Φ_Al^R and thus their mechanism and sorption capacity.     

A block copolymer covalent coating acting as surfactants in separation of 2-[hydroxy(4-nitrophenyl)methyl]-cyclopent-2-enone and 4-nitrobenzaldehyde by capillary electrophoresis

An innovative block copolymer capillary coating P(MAn-alt-St)₁₂₇-b-PSt₅₉₂, synthesized by maleic anhydride and styrene, was developed as a new kind of coating for capillary electrophoresis. The covalent bond coating was effectively applied in the separation of raw material (4-nitrobenzaldehyde) and production (2-[hydroxy(4-nitrophenyl)methyl]-cyclopent-2-enone) in a Baylis-Hillman reaction using ammonium acetate with 20% tetrahydrofuran (v/v) as the buffer solution. Electroosmotic flow measurement gave an instantly stable value after 70 times continued injection in 5 days and showed that P(MAn-alt-St)₁₂₇-b-PSt₅₉₂ coatings could suppress electroosmotic flow effectively compared with the bare capillary. The effects of tetrahydrofuran and the pH of buffer on the separation were investigated. The characteristics of the coatings to form micelles similar to surfactants were detected by atomic force microscopy. Moreover, the superiority of this coating was further applied in the separation of four aromatic amines.     

Assessing the MALDI-TOF MS sample preparation procedure to analyze the influence of thermo-oxidative ageing and thermo-mechanical degradation on poly (Lactide)

Multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PLA under mechanical recycling. Likewise, an accelerated thermal ageing over PLA glass transition was performed in order to simulate its service life. MALDI-TOF MS was used for the analysis and the sample preparation procedure was assessed by means of a statistical Design of Experiments (DoE). The quality effects in use for the analysis were signal-to-noise ratio and Resolution. Different matrixes, analyte/matrix proportions and the use of NaTFA as cationization agent were considered. A deep inspection of the statistical results provided a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measurement of PLA stated that the best combination of factors (levels) was the following: matrix (s-DHB), proportion analyte/matrix (1/5 V/V), and no use of cationization agent. Degradation primarily affected the initially predominant cyclic [LA_C]_n and linear H[LA_L]_nOH species, where LA stands for a PLA repeating unit. Intramolecular and intermolecular transesterifications as well as hydrolytic and homolytic reactions took place during the formation and disappearance of oligomeric species. In both degradation mechanisms induced by thermal ageing and thermo-mechanical degradation, the formation of H[LA_L]_nOCH₃ by intermolecular transesterifications was highlighted.     

Review on recent and advanced applications of monoliths and related porous polymer gels in micro-fluidic devices

This review critically summarises recent novel and advanced achievements in the application of monolithic materials and related porous polymer gels in micro-fluidic devices appearing within the literature over the period of the last 5 years (2005-2010). The range of monolithic materials has developed rapidly over the past decade, with a diverse and highly versatile class of materials now available, with each exhibiting distinct porosities, pore sizes, and a wide variety of surface functionalities. A major advantage of these materials is their ease of preparation in micro-fluidic channels by in situ polymerisation, leading to monolithic materials being increasingly utilised for a larger variety of purposes in micro-fluidic platforms. Applications of porous polymer monoliths, silica-based monoliths and related homogeneous porous polymer gels in the preparation of separation columns, ion-permeable membranes, preconcentrators, extractors, electrospray emitters, micro-valves, electrokinetic pumps, micro-reactors and micro-mixers in micro-fluidic devices are discussed herein. Procedures used in the preparation of monolithic materials in micro-channels, as well as some practical aspects of the micro-fluidic chip fabrication are addressed. Recent analytical/bioanalytical and catalytic applications of the final micro-fluidic devices incorporating monolithic materials are also reviewed.     

Thermodynamic and spectroscopic study of the interaction of Cu(II), Ni(II), Zn(II) and Ca(II) ions with 2-amino-N-(2-oxo-2-(2-(pyridin-2-yl)ethyl amino)ethyl)acetamide,a pseudo-mimic of human serum albumin

The protonation equilibria of 2-amino-N-(2-oxo-2-(2-(pyridin-2-yl)ethyl amino)ethyl)acetamide ([H₂(556)–N]) and the complexation of this ligand with Cu(II) Ca(II), Zn(II) and Ni(II) have been studied by glass electrode potentiometry and UV–visible spectrophotometry. From pH ∼2.00–11.00, five models for Cu(II) with the following complexes; MLH, ML, MLH₋₁, MLH₋₂ and MLH₋₃ were generated and observed to describe the experimental data equally well as far as the statistical criteria were concerned. The MLH₋₂ complex predominates at physiological pH in all five models, while the MLH₋₁ complex species exists only at low concentration in two models. The coordination in the MLH₋₂ complex suggested the involvement of one amino, two deprotonated peptides and one pyridyl nitrogen atoms. Molecular mechanics (MM) calculations confirmed the MLH₋₂ complex as the most stable species. Speciation calculations, using a blood plasma model, predicted that the Cu(II)–[H₂(556)–N] complex is able to mobilize Cu(II). Octanol/water partition of CuLH₋₂ showed that 30% of the complex went into the octanol phase, hence promoting percutaneous absorption of copper. The complex is a poor mimic of native copper–zinc superoxide dismutase.