超分子凝胶性质与溶剂参数关系的研究进展

为了能有效地开发功能性凝胶, 人们对超分子凝胶机理做了大量研究. 但目前的研究还局限于凝胶因子结构和外界环境等影响因素, 而有关溶剂对超分子凝胶体系的影响规律还不十分清楚. 本文将结合最新研究进展详细地讨论凝胶性质(如凝胶-溶胶转变温度(T_gel)、临界凝胶浓度(CGC)、凝胶流变学性质等)与溶剂参数(如ε、E_T(30)、χ、δ、δ_d、δ_p、δ_h等)的关系, 揭示溶剂影响凝胶性质的规律; 在此基础上, 进一步介绍了超分子凝胶行为预测模型: 一维模型、Teas图模型和Hansen空间模型, 并讨论了各模型的优缺点, 以期为新型超分子凝胶体系的设计提供参考.     

含密胺基团新型酰胺类凝胶因子的合成、性能及Hansen溶度参数对凝胶行为的预估

设计合成了一种含有密胺基团的新型酰胺类凝胶因子AMOG,其在多种常用有机溶剂中均能形成凝胶,且在甲苯和二甲苯中形成凝胶的临界凝胶浓度(CGC)约为1 mmol/L.采用"试管倒转法"确定了凝胶的溶剂-凝胶转变温度(Tgel),利用SEM表征了凝胶的微观结构,发现AMOG具有明显的溶剂效应.运用溶剂的Hansen溶度参数探索溶剂对凝胶行为的作用机制,发现溶剂的氢键作用参数(δh)对凝胶的微观结构和凝胶性质有显著影响:AMOG在1.0 MPa~(1/2)δh4.1 MPa~(1/2)的溶剂中形成透明凝胶,在4.1 MPa~(1/2)δh8.0MPa~(1/2)的溶剂中为不透明凝胶,在δh8.0 MPa~(1/2)的溶剂中为沉淀或溶液状态.进一步将溶剂的Hansen溶度参数以三维坐标(δ_d,δ_p和δ_h)表示,发现能使AMOG形成凝胶的溶剂主要集中在Hansen空间的特定区域内.实验结果表明,凝胶体系的溶液-凝胶转变温度主要受色散参数δ_d与极性参数δ_p的影响,氢键参数δh对其有微调的作用.     

凝胶过程参数与溶剂极性参数之间的关系探讨

在机凝胶自组装过程中,最低凝胶化浓度MGC是一个重要的表征参数。基于文献报道的凝胶化过程中最低凝胶化浓度MGC值,并引入Kamlet和Taft定义的溶剂极性参数β对MGC做图,发现上述两者之间总是呈现一种线性关系。这种线性关系可以描述为:MGC=Aβ+B,其中A、B为两个常数。在对系数进一步探讨后,发现所有模型中的A值都为正数,即β与MGC值成正比关系。而不同模型中B值的差异明显,这说明其可能与凝胶剂的结构有关。     

超分子聚合物凝胶

作为非常重要的软物质材料,超分子聚合物凝胶代表了一个全新的概念和更复杂的凝胶体系.这种新型的超分子体系的构建,是基于多种非共价相互作用协同的多层次组装.即小分子构筑基元首先组装成为超分子聚合物,而这些非共价聚合物的多层次组装形成凝胶的纳米结构.超分子聚合物凝胶无论是在结构上,还是在性能上都具有很多崭新的特点.因此,尽管有关超分子聚合物凝胶的研究开展的时间还很短,这一体系所表现出的独特性以及巨大潜力已经引起科学家们越来越广泛的关注.本文简要综述了这一领域的最新进展.主要论述基于多种非共价相互作用的超分子聚合物凝胶的构建以及对其力学性能的调控.     

超分子金属凝胶

近年来,超分子凝胶已逐渐发展为一类具有广阔应用前景的智能/功能性纳米材料。目前研究的大部分超分子凝胶利用的是氢键或者分子堆积作用,而配位键这一在超分子化学中同样重要的作用在凝胶合成上的应用则远远不足。由于引入金属离子后能够给凝胶带来光电、催化、氧化还原等新的性能,因此超分子金属凝胶的研究也在近年来得到升温。本文首先给出超分子金属凝胶的定义,接着通过实例具体介绍基于凝胶因子和配位聚合物两种形式的超分子金属凝胶,将分子结构特别是其中的配体基团、所用金属离子和凝胶的性质、功能联系起来,最后简介异常的超分子金属凝胶行为。     

超分子凝胶:结构多样性与超分子手性

超分子凝胶作为一种重要的软物质材料,在构建多重刺激响应性、光电功能,以及生物相容材料等功能软物质方面表现出了独特的优越性。超分子凝胶在形成过程中往往得到比较均一的纳米结构,且具有结构多样性;而另一方面,超分子凝胶的构筑单元大部分是手性分子,超分子凝胶也是实现手性在超分子层次/纳米层次表达的重要途径,尤其是手性传递、手性放大、不对称催化方面,同时超分子凝胶也是构筑手性纳米结构的重要手段。本文主要对超分子凝胶形成中的纳米结构以及形貌的多样性和超分子手性进行介绍,并展望该领域未来的发展方向。     

胆酸超分子凝胶化学

胆酸来源丰富,价格低廉,在生命过程中发挥着重要的作用。与胆固醇不同,胆酸以其结构和修饰途径的多样性,以及独特的双亲结构备受超分子化学工作者关注。近年来以胆酸为基本构筑单元的小分子胶凝剂创制及其相关凝胶的研究取得了重要的进展。本文从胆酸衍生物结构设计到胆酸衍生物凝胶构建,概要介绍了胆酸超分子凝胶及其性能研究进展。在此基础上,简要阐述胆酸超分子凝胶材料的潜在应用。     

超分子凝胶中的光化学反应

超分子凝胶中的光化学反应是比较特殊的一类反应,通常是将具有光响应活性的基团或分子引入到超分子凝胶的自组装体系中,因此,能够将超分子凝胶独特的性质与光化学反应的优势有效地结合起来,构筑新型的光功能材料,这使得此类超分子凝胶在光信息存储、光开关及光转换器件等前沿领域具有广阔的应用前景.本文主要总结近年来国内外包括作者课题组对超分子凝胶中光化学反应方面的研究进展,以及其在多重响应凝胶、手性光学开关以及手性合成方面的应用.     

由凝胶因子形成的十四酸异丙酯超分子凝胶制备与表征

采用双十八烷基-L-苯丙氨酸(Bis18-L-Phe)为凝胶因子,制备了具有热可逆性的十四酸异丙酯(IPM)超分子凝胶。IPM凝胶相转变温度(Tgel)随Bis18-L-Phe浓度增大而增加。偏光显微镜(POM)显示在整个IPM凝胶中形成了相互缠绕的针状聚集体。FT-IR光谱分析表明Bis18-L-Phe分子间酰胺的氢键作用是IPM凝胶形成的一个重要驱动力。IPM凝胶动力学研究表明凝胶时间随Bis18-L-Phe浓度的增大而缩短,随着温度升高而延长,因此IPM凝胶时间可以通过温度和Bis18-L-Phe浓度调控。     

超分子溶剂在样品前处理与检测技术中的应用研究进展

随着绿色分析化学概念的提出,新型绿色溶剂的开发和利用成为当前的研究热点.将绿色溶剂替代传统有机溶剂用于样品前处理过程,可以减少对实验人员及环境的危害.超分子溶剂由于两亲物质含量高,萃取分离条件温和,近年来被广泛应用于萃取富集宽极性范围内的目标分析物,兼具萃取和净化的效果.该文介绍了超分子溶剂的形成过程和基本性质,综述了...     

Progress in Molecular Dynamics and Hansen Solubility Parameters of Low Molecular Weight Gels北大核心CSCD

Recently,the use of computational methods such as Molecular Dynamics（MD）simulations and Hansen Solubility Parameters （HSPs）to study the behavior of small molecule gelators has attracted much attention. MD simulation is a computational method based on classical mechanics and is one of the preferred techniques for understanding the process of small molecule gelators. The MD simulation can more accurately analyze the gelation trend or assembly behavior of small molecule gelators,dynamically and graphically display the self-assembly process,effectively reveal the relationship between the structure of small molecule gelators and related gelation behavior,and quantitatively analyze non-covalent bond interactions such as hydrogen bonds,π-π stacking,van der Waals interactions,ionic bonding and solvophobic interactions. By performing molecular dynamics simulations on known gelators/non-gelators,parameters related to gelation behavior in the simulated data are extracted,and the linear correlation is measured by fitting the Pearson correlation coefficient to finally predict the gelation behavior of a certain class of small molecules. On the other hand,the empirical model developed according to the HSPs is the most representative,which consists of the energy of dispersion interaction（δd）,the energy of polar interaction（δp）and H-bonding energy（δh ）between molecules. These three parts determine the coordinate point of the three-dimensional space（Hansen space）. According to the range of the point,it can be determined whether the organic small molecule can form a gel in a specific solvent. In this paper,representative works published recently in the field of organic small molecule gels by using MD simulations and empirical models are reviewed. Some comments on the assembly behavior of gelators,the regulation and prediction of non-covalent bond interactions on gelation ability are made. © 2022, Science Press (China). All rights reserved.     

A new way to determine the three-dimensional solubility parameters of hydrogenated nitrile rubber and the predictive power

In order to understand the swelling behavior of hydrogenated nitrile rubber (HNBR) more fully, the total solubility parameters (δ_t) of HNBR (Therban 2568) were determined by equilibrium swelling tests. Then, the swelling responses were analysed by a computer program to determine the Hansen three-dimensional solubility parameter (HSP). The HSP values – determined from lightly cured rubber samples – were estimated as δ_d = 18.4 (J/cm³)^1/2, δ_p = 6.0 (J/cm³)^1/2, δ_h = 4.5 (J/cm³)^1/2 and δ_t = 19.9 (J/cm³)^1/2. The energy difference (Ra) between HNBR and solvents or solvent mixtures have been calculated by their HSP values and proven to be useful for predicting the swelling behaviour of HNBR. The swelling volume decreases with increasing Ra values. Using blended solvents, a clear correlation between Ra values and the rubber swelling response was established. Thus, it may be possible to use the Hansen three-dimensional solubility parameters to predict swelling phenomena of cured rubber articles in mixed fluids such as bio-fuels or lubricants. Also, the HSP values may be used to predict the response of rubber seals or gaskets when replacing toxic or expensive fluids with more favorable environmentally friendly or inexpensive ones.     

Solubility Determination,Hansen Solubility Parameters and Thermodynamic Evaluation of Thymoquinone in (Isopropanol + Water) Compositions

This article studies the solubility, Hansen solubility parameters (HSPs), and thermodynamic behavior of a naturally-derived bioactive thymoquinone (TQ) in different binary combinations of isopropanol (IPA) and water (H₂O). The mole fraction solubilities (x₃) of TQ in various (IPA + H₂O) compositions are measured at 298.2–318.2 K and 0.1 MPa. The HSPs of TQ, neat IPA, neat H₂O, and binary (IPA + H₂O) compositions free of TQ are also determined. The x₃ data of TQ are regressed by van’t Hoff, Apelblat, Yalkowsky–Roseman, Buchowski–Ksiazczak λh, Jouyban–Acree, and Jouyban–Acree–van’t Hoff models. The maximum and minimum x₃ values of TQ are recorded in neat IPA (7.63 × 10⁻² at 318.2 K) and neat H₂O (8.25 × 10⁻⁵ at 298.2 K), respectively. The solubility of TQ is recorded as increasing with the rise in temperature and IPA mass fraction in all (IPA + H₂O) mixtures, including pure IPA and pure H₂O. The HSP of TQ is similar to that of pure IPA, suggesting the great potential of IPA in TQ solubilization. The maximum molecular solute-solvent interactions are found in TQ-IPA compared to TQ-H₂O. A thermodynamic study indicates an endothermic and entropy-driven dissolution of TQ in all (IPA + H₂O) mixtures, including pure IPA and pure H₂O.     

Kinetic Studies of Solvent and Pressure Effects on the Thermal Isomerization of Palladium Dithizonate

IntroductionThe photo-and thermo-chromisms of organometallic compounds have been intensivelystudied during thelast1 0 years.Meriwetheretal.[1 ,2 ] examined the chromic behaviorofmet-al-dithizone(phenyldiazenecarbothionic acid2 -phenylhydrazide) complexesin detail.From thekinetic and infrared studies,they showed thatthe central metal of a dithizonate complex de-termined the photochemical stability,the rate of the thermal return reaction,and the colorofthe dithizonate complex.As reported by Mer…     

Definition of Hydration Parameters in the Region of Maximal Solvent Density

The approach to the definition of hydration numbers using the ultraacoustic method is critically discussed. Leaning upon a correct thermodynamic analysis, limited validity is shown of the main equation used in the publication of Onori over a wide range of state parameters. It is revealed that the mentioned equation is true only in the region of maximum solvent density. For this range of conditions, hydration numbers, the compressibility of hydration formations, molar volume and compressibility of water in hydration shells, molar volume and compressibility of stoichiometric mixtures of ions of NaCl are calculated based upon the experimental data of density and speed of ultrasound in solutions.     

吡嗪二羧酸-三聚氰胺双组分水凝胶的制备及性能

以3,6-二甲基-2,5-吡嗪二羧酸(P)和三聚氰胺(M)为组分,采用不同的摩尔比(1∶1,1∶2,1∶3)混合配制了3个样品PM11,PM12和PM13,并对其凝胶性能进行了测试.实验结果表明,PM能在水中及部分含水有机溶剂中形成稳定的凝胶,这些凝胶对酸碱具有良好的响应性能.采用扫描电子显微镜分析了3种水凝胶的微观形貌,均为纤维状的网络结构;红外光谱及紫外光谱测试结果表明氢键是形成凝胶的关键驱动力;XRD测试结果显示凝胶为层状结构.对PM12在不同pH值的水中的凝胶性能测试结果表明,在pH=3~11的范围内PM12均能形成凝胶.测试了PM12在混合溶剂中的凝胶性能,并将测试结果与混合溶剂的Hansen溶解度参数关联,以便用于分析溶剂与凝胶因子间的相互作用,所得结果亦表明氢键在凝胶形成的过程中起重要作用.     

Solvent effects on chemical processes. 4. Complex formation between naphthalene and theophylline in binary aqueous-organic solvents

The standard free energy change for complex formation is written as a sum of effects arising from solvent-solvent interactions (the general medium effect), solvent-solute interactions (the solvation effect), and solute-solute interactions (the intersolute effect). The general medium effect is given by gA(–_o), where g is a curvature correction factor to the solvent surface tension , A is the change in surface area as the two solvent cavities containing the substrate (naphthalene) and ligand (theophylline) collapse into a single cavity containing the complex, and _o is the value of surface tcnsion at which there is no net solvophobic interaction; is defined to be the value appropriate to the equilibrium mean solvation shell composition. The solvation effect is modeled by equilibrium stoichiometric formation of solvated species. All data are related to the fully aqueous system to give _MG^o, the solvent effect on the free energy change, as an explicit function of solvent composition. Solvent effects on bimolecular association are related to solvent effects on the solubilities of the substrate, ligand, and complex. Approximation methods for interpreting such systems are described and are applied to the naphthalene-theophylline complex. It is shown that complex destabilization in mixed aqueous-organic solvents (relative to the fully aqueous system) may receive contributions from both the general medium and the solvation effects, and that these contributions can be quantitatively estimated.     

Isavuconazole: Thermodynamic Evaluation of Processes Sublimation,Dissolution and Partition in Pharmaceutically Relevant Media

A temperature dependence of saturated vapor pressure of isavuconazole (IVZ), an antimycotic drug, was found by using the method of inert gas-carrier transfer and the thermodynamic functions of sublimation were calculated at a temperature of 298.15 K. The value of the compound standard molar enthalpy of sublimation was found to be 138.1 ± 0.5 kJ·mol⁻¹. The IVZ thermophysical properties—melting point and enthalpy—equaled 302.7 K and 29.9 kJ mol⁻¹, respectively. The isothermal saturation method was used to determine the drug solubility in seven pharmaceutically relevant solvents within the temperature range from 293.15 to 313.15 K. The IVZ solubility in the studied solvents increased in the following order: buffer pH 7.4, buffer pH 2.0, buffer pH 1.2, hexane, 1-octanol, 1-propanol, ethanol. Depending on the solvent chemical nature, the compound solubility varied from 6.7 × 10⁻⁶ to 0.3 mol·L⁻¹. The Hansen s approach was used for evaluating and analyzing the solubility data of drug. The results show that this model well-described intermolecular interactions in the solutions studied. It was established that in comparison with the van’t Hoff model, the modified Apelblat one ensured the best correlation with the experimental solubility data of the studied drug. The activity coefficients at infinite dilution and dissolution excess thermodynamic functions of IVZ were calculated in each of the solvents. Temperature dependences of the compound partition coefficients were obtained in a binary 1-octanol/buffer pH 7.4 system and the transfer thermodynamic functions were calculated. The drug distribution from the aqueous solution to the organic medium was found to be spontaneous and entropy-driven.