共查询到20条相似文献,搜索用时 171 毫秒
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本文研究以非离子型表面活性剂-正辛醇-水-芳烃类所组成的微乳液,探讨醇从油相转移到界面相时的自由能变化,以及温度对自由能的影响。计算出熵和焓的变化,发现在实验范围内,上述热力学函数的对数值与芳烃侧链的碳原子数(n)呈线性关系: ln(-⊿G_(30°O)~0,s→i)=-8.67+0.118n ln⊿H_(s→i)=12.0-0.604n ln⊿S_(s→i)~0=6.32-0.55n 这些关系式对微乳液的构成和稳定性的讨论是重要的,还对几种芳烃异构体所构成的微乳液的热力学函数进行了实验和讨论。 相似文献
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本文研究了由非离子型表面活性剂、水、甲苯和醇所组成的微乳液,发现醇的烃链上碳原子数直接与热力学函数成线性关系,氧乙烯基团数与自由能、焓以及熵的对数值亦成线性关系。这些结果对研究微乳液的构成和稳定性很有意义。 相似文献
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咪唑啉型表面活性剂组成微乳液的热力学性质 总被引:3,自引:0,他引:3
由咪唑啉型表面活性剂、醇、水和正十六烷组成微乳液,探讨了该微乳液中醇从油相转移到界面相时的自由能变化及温度对自由能变化的影响,算得了熵变和焓变。 相似文献
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用稀释法研究了自制的6种不同结构的烷基芳基磺酸盐(AAS)在多组分体系中形成微乳液的标准热力学函数,并考察了分子结构、温度、短链醇、含水量和无机盐含量对其的影响。 结果表明,随着烷基芳基磺酸盐分子长烷基链碳原子数的增加,导致表面活性剂/正丁醇/正癸烷/水形成的微乳液体系中醇由油相转移到界面相的标准自由能ΔG0o→i减小,有利于微乳液的形成;ΔH0o→i无明显变化,ΔS0o→i增大,且与烷基链碳原子数呈线性关系。 ΔS0o→i=1.7975n+71.538。 随着表面活性剂分子芳环向烷基链中间位置移动,导致表面活性剂/正丁醇/正癸烷/水形成的微乳液体系中醇由油相转移到界面相的标准自由能ΔG0o→i减小,有利于微乳液的形成;ΔS0o→i增大,ΔH0o→i减小;温度的升高导致微乳液体系的ΔG0o→i减小,微乳液的形成更容易。随醇碳链上碳原子数增加,ΔG0o→i减小,有利于微乳液的形成,且ΔG0o→i与碳原子数n呈线性关系,ΔG0o→i=-2790.8n+7286.4(328 K);含水量的增加导致ΔG0o→i增大,不利于微乳液的形成,且ΔG0o→i与含水量V也呈线性关系。 ΔG0o→i=6697.8V-7170.4(318 K);无机盐浓度的增加导致ΔG0o→i减小,有利于微乳液的形成。 相似文献
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采用室温反相微乳液法制备了3种不同尺寸的花生状微/纳米CaMoO4.基于纳米CaMoO4与块体CaMoO4热力学性质的本质差异,结合化学热力学基本理论及热动力学原理,推导出纳米CaMoO4摩尔表面热力学函数的关系式.在此基础上,采用原位微量热技术获得了花生状微/纳米CaMoO4的摩尔表面热力学函数.结果表明,花生状微/纳米CaMoO4的表面热力学性质变化具有尺寸效应,即随着尺寸的减小,摩尔表面焓、摩尔表面Gibbs自由能、摩尔表面熵均增加. 相似文献
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Palombo F Sassi P Paolantoni M Morresi A Cataliotti RS 《The journal of physical chemistry. B》2006,110(36):18017-18025
Liquid 1-octanol and 2-octanol have been investigated by infrared (IR), Raman, and Brillouin experiments in the 10-90 degrees C temperature range. Self-association properties of the neat liquids are described in terms of a three-state model in which OH oscillators differently implicated in the formation of H-bonds are considered. The results are in quantitative agreement with recent computational studies for 1-octanol. The H-bond probability is obtained by Raman data, and a stochastic model of H-bonded chains gives a consistent picture of the self-association characteristics. Average values of hydrogen bond enthalpy and entropy are evaluated. The H-bond formation enthalpy is ca. -22 kJ/mol and is slightly dependent on the structural isomerism. The different degree of self-association for the two octanols is attributed to entropic factors. The more shielded 2-isomer forms larger fractions of smaller, less cooperative, and more ordered clusters, likely corresponding to cyclic structures. Signatures of a different cluster organization are also evidenced by comparing the H-bond energy dispersion (HBED) of OH stretching IR bands. A limiting cooperative H-bond enthalpy value of 27 kJ/mol is found. It is also proposed that the different H-bonding capabilities may modulate the extent of interaggregate hydrocarbon interactions, which is important in explaining the differences in molar volume, compressibility, and vaporization enthalpy for the two isomers. 相似文献
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K. S. Birdi 《Colloid and polymer science》1982,260(6):628-631
In microemulsions consisting of four components, i.e. detergent — water — oil — cosurfactant, the free energy of transfer from the continuous oil phase to the interfacial region for the cosurfactant is reported. From the effect of temperature on the free energy, the entropy and the enthalpy values are also reported. The effect of chain length of the alcohol (cosurfactant) is also described. It is further shown, that if the oil phase consists of hexadecane, then the free energy changes as a linear function of the number of carbon atoms in the cosurfactant. On the other hand, if the oil phase is benzene, the cosurfactant chain length has very little effect. These data are analyzed with respect to the microemulsion structure and stability. 相似文献
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Axel Bidon-Chanal Oscar Huertas Modesto Orozco F. Javier Luque 《Theoretical chemistry accounts》2009,123(1-2):11-20
The balance between electrostatic and non-electrostatic enthalpic contributions to the free energy of solvation of a series of neutral solutes in water and n-octanol is examined by means of continuum solvation calculations based on the Miertus–Scrocco–Tomasi (MST) method. The experimental data indicate that the solvation enthalpy of hydrocarbons is very similar in water and n-octanol, and that the enthalpic contribution measured for polar compounds is larger in water than in n-octanol. According to MST calculations, the different magnitude of the solvation enthalpy found for polar compounds in the two solvents can be largely attributed to the electrostatic contribution. Moreover, the results point out that there is close resemblance between the non-electrostatic components for both hydrocarbons and polar compounds in the two solvents. Finally, the results show the power of current continuum models like MST to dissect the total free energy of solvation in entropic and enthalpic contributions and suggest that new refinements of continuum solvation models should include not only the fitting to solvation free energies, but also their enthalpic components. 相似文献
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Giuseppina Castronuovo Marcella Niccoli 《Journal of Thermal Analysis and Calorimetry》2011,103(2):641-646
The formation of complexes of parent and alkylated cyclodextrins (CDs) with 1-heptanol and 1-octanol has been studied calorimetrically
at 298 K in water and in concentrated aqueous solutions of urea. The forces involved in the association process are discussed
in the light of the signs and values of the thermodynamic parameters obtained: association enthalpy, binding constant, Gibbs
free energy, and entropy. It was inferred that: (i) in water, the formation of complexes for parent and substituted α-cyclodextrins
(αCDs) is determined by enthalpy. For parent and substituted β-cyclodextrins (βCDs), instead, hydrophobic interactions are
the prevailing forces determining complexation, as indicated by the small and negative or positive enthalpies and by the high
and positive entropies. (ii) In urea, hydrophilic interactions are attenuated. The formation of complexes with alkylated CDs
does not occur. (iii) The analysis of the thermodynamic properties confirms that inclusion is a process dominated by hydration phenomena.
Modifications experienced by the solvent water in the hydration shells of the interacting substances upon association determine
the formation of the complexes. 相似文献
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Alan L. Myers 《Adsorption》2003,9(1):9-16
Desorption functions (G, H, S) are useful for adsorbent characterization, phase equilibria, and enthalpy and entropy balances. Adsorption isotherms, enthalpy, and entropy are temperature and pressure derivatives of the free energy, so that G(T, P) is an adsorption equation-of-state which contains complete thermodynamic information about the system. The free energy of desorption is the minimum isothermal work necessary to regenerate the adsorbent. The free energy of desorption also determines the selectivity of an adsorbent for different gases. The ideal enthalpy of desorption for a mixture (H =
i
n
i
h°
i
) is a simple function of the enthalpies of desorption for the individual components. Sample calculations of the free energy, enthalpy, and entropy desorption functions are provided for pure components and mixtures. 相似文献
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[trans-5,15-Bis(2,7-dihydroxy-1-naphthyl)-2,3,7,8,12,13,17,18-octaethylporphyrinato]zinc(II) (1), a trifunctionalized porphyrin host, was prepared as a receptor for amino acid derivatives, particularly those having a hydrogen-bonding site in the side chain. The free energy changes for the binding of Leu-OMe, Asp-OMe, and Glu-OMe to 1 were -5.8 kcal/mol, -6.6 kcal/mol, and -5.9 kcal/mol, showing a selectivity for Asp-OMe. (1)H NMR titration experiments indicated that three simultaneous attractive interactions, one coordination interaction, and two hydrogen-bonding interactions, are operating in the host-guest complex. The preference for Asp-OMe over Glu-OMe was found to originate from the favorable enthalpy term for Asp-OMe. The free energy change, the enthalpy change, and the entropy change were determined and split into contributions arising from coordination interaction and from hydrogen-bonding interactions by use of reference hosts. Comparison of enthalpy and entropy changes suggests that the host-guest complex becomes more ordered as the number of recognition pairs increases. 相似文献
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In this study, polymers of sodium 10-undecenoyl L-leucinate (SUL) and sodium undecenyl sulfate (SUS) as well as their copolymerized molecular micelles (CoPMMs) were applied in MEKC as pseudostationary phases to separate benzodiazepines and alkyl phenyl ketones. SDS, a common pseudostationary phase used in MEKC, was also used for comparison. The van't Hoff relationship was applied to compute the temperature dependence of the MEKC retention factors of the test solutes to estimate the enthalpy, entropy, and the Gibbs free energy. Nonlinear van't Hoff plots were obtained with the majority of benzodiazepines indicating that the thermodynamic parameters were temperature-dependent in all surfactant systems for these solutes. In contrast, all alkyl phenyl ketones resulted in linear van't Hoff plots. 相似文献
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Thermodynamics of surfactant-dye complex formation have been studied, in terms of equilibrium coefficient, using a spectrophotometer. The systems are 6 sodium alkyl sulfates, which have different alkyl chain lengths, and 4-phenylazo-1-naphthylamine. A pronounced spectral change in the dye solution occurs on addition of the surfactant; the change has a definite isosbestic point and a new absorption band at 535 nm because of surfactant-dye complex formation, which is caused by hydrophilic-hydrophilic interaction. As the alkyl chain length in the surfactant increases, the values of free energy change (negative) increase, while the value of enthalpy change (negative) increases and the value of entropy change (positive) decreases. The longer the alkyl chain length in surfactant increase, the more stable the surfactant-dye complex becomes.Surfactant-dye complex will form due to hydrophilic-hydrophilic interaction and will become more stable due to hydrophobic-hydrophobic interaction. 相似文献
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A modified Miedema model, using interrelationship among the basic properties of elements Ti and H, is employed to calculate the standard enthalpy of formation of titanium hydride TiHx (1≤x≤2). Based on Debye theories of solid thermal capacity, the vibrational entropy, as well as electronic entropy, is acquired by quantum mechanics and statistic thermodynamics methods, and a new approach is presented to calculate the standard entropy of formation of TiH2. The values of standard enthalpy of formation of TiHx decrease linearly with increase of x. The calculated results of standard enthalpy, entropy, and free energy of formation of TiH2 at 298.16 K are -142.39 kJ/mol, -143.0 J/(mol?K) and -99.75 kJ/mol, respectively, which is consistent with the previously-reported data obtained by either experimental or theoretic 相似文献