Prediction on Critical Micelle Concentration of Nonionic Surfactants in Aqueous Solution： Quantitative Structure-Property Relationship Approach

IntroductionCriticalmicelleconcentration (cmc)ofsurfactantsinaqueoussolutionisoneofthemostusefulparametersforcharacterizingthepropertiesofsurfactants.Overaverynarrowconcentrationrangearoundthecmctransitionsoftheexistenceofsurfactantsoccurfrommonomer ,premicel lartomicellar .Andcompanyingthesetransitions ,manyotherimportantpropertiesofsurfactantsolution ,suchassurfacetension ,interfacialtension ,conductivity ,osmoticpressure ,detergency ,emulsification ,foamingandsoon ,alsochangesharplyatthepoi…     

Synthesis of Some Surfactants Based on Polytriethanolamine and Investigation of Their Surface Active Properties

New modified surfactants were developed by esterification of ethoxylated polytriethanolamine with oleic acid. Triethanolamine was polymerized at three different times 1.30, 2.30, and 3.30 hours to give (P₄, P₆, and P₈) where 4, 6, and 8 refer to the degree of polymerization. The prepared polymer (P₈) was ethoxylated at three different molar ratios of ethylene oxide (40, 100, and 120) and named E(en)P₈. Then the ethoxylated polymers were esterified with oleic acid and abbreviated as E(en)P₈O_m. The surface properties for these surfactants were determined by measuring the surface tension. The structure was confirmed using the elemental analysis, (FTIR, ¹H, ¹³C NMR) spectroscopic.     

The New Descriptors Effective on the Detonation Performance of Aluminized Explosives

The relationship between detonation velocity and the elemental composition of components of aluminized explosives are assessed through quantitative structure-property relationship (QSPR). Here, two new reliable, simple models are proposed for estimating aluminized explosives detonation heat and velocity based on molecular structure by applying QSPR. In this methodology it is assumed that these two detonation parameters can be presented as a function of elemental composition, density and several structural parameters. This new correlation of heat detonation has determination coefficient of 0.930, root mean square deviation (RMSD) of 324.4 and average absolute deviation (AAD) of 446kJ · kg^–1 for 36 aluminized explosives with different molecular structures as the training set. The predictive power of this new correlation is checked through a cross validation method. Statistical parameters reveal relatively good result for this correlation. Also, the determination coefficient of detonation velocity for the other new model is 0.960 and it has 151.1 (RMSD) and 107.9 m · s^–1 (AAD) for 42 aluminized explosives with different molecular structures as training set. Reliability and validity of new correlation investigated (Q²_Ext = 0.948, Q²_LOO = 0.938, and Q²_LMO = 0.937). The good ability of this new model for prediction detonation velocity of aluminized explosives are confirmed.     

Anionic–Nonionic Mixed Surfactant Systems: Micellar Interaction and Thermodynamic Behavior

The interactions between an anionic surfactant, viz., sodium dodecylbenzenesulfonate and nonionic surfactants with different secondary ethoxylated chain length, viz., Tergitol 15-S-12, Tergitol 15-S-9, and Tergitol 15-S-7 have been studied in the present article. An attempt has also been made to investigate the effect of ethoxylated chain length on the micellar and the thermodynamic properties of the mixed surfactant systems. The micellar properties like critical micelle concentration (CMC), micellar composition (X_A), interaction parameter (β), and the activity coefficients (f_A and f_NI) have been evaluated using Rubingh's regular solution theory. In addition to micellar studies, thermodynamic parameters like the surface pressure (Π_CMC), surface excess values (Γ_CMC), average area of the monomers at the air–water interface (A_avg), free energy of micellization (ΔG_m), minimum energy at the air–water interface (G_min), etc., have also been calculated. It has been found that in mixtures of anionic and nonionic secondary ethoxylated surfactants, a surfactant containing a smaller ethoxylated chain is favored thermodynamically. Additionally, the adsorption of nonionic species on air/water interface and micelle increases with decreasing secondary ethoxylated chain length. Dynamic light scattering and viscometric studies have also been performed to study the interactions between anionic and nonionic surfactants used.     

Adsorption of Pure Nonionic Alkylethoxylated Surfactants down to Low Concentrations at a Silica/Water Interface as Determined Using a HPLC Technique

The adsorption of pure nonionic alkylethoxylated surfactants of the C₁₂E_nseries at silica/water interface has been determined using a very precise HPLC technique. The number of ethoxylated groups was varied from 2 to 9. The adsorption isotherms were constructed with special attention to the very low surface coverage domain. It is shown that at very low concentration, the adsorption amounts are higher as the number of ethoxylated groups increases but the reverse trend is found at higher surfactant concentration and above the critical micelle concentration. It is shown that this behavior is the consequence of the interplay of the primary and secondary adsorption mechanisms depending upon the length of the ethoxylated chain. The maximum adsorption quantities is not a linear function of the number of ethoxylated groups. This and other observations confirm the viewpoint that the behavior of nonionic surfactant aggregates adsorbed at a hydrophilic surface carries many similarities with the properties of this class of nonionic surfactant aggregates in bulk aqueous solutions.     

13C NMR assignments of nonionic and anionic ethoxylated surfactants

¹³C chemical shift assignments have been made for the ethoxy region of nonionic and anionic ethoxylated surfactants. The lanthanide shift reagent Eu(fod)₃ was used to assign the shifts of nonionics because of some ambiguities in the literature.     

拓扑指数与烷烃色谱保留指数的定量相关研究

基于分子图论, 计算了64个链烷烃的一阶连接性指数(¹χ)和奇偶指数(OEI), 并对气相色谱保留指数进行定量结构-性质相关(QSPR)研究, 得到多元线性回归模型RI＝55.7631＋25.7317OEI＋111.4508¹χ (R²＝0.9960, RMS＝9.36, ARD＝1.02%). 交叉验证和预测结果表明, 所建立的QSPR模型具有良好的稳定性和预测能力. 与文献结果比较, 本文所用的参数少, 且计算简便.     

Using the QSPR Approach for Estimating the Density of Azole‐based Energetic Compounds

The relationship between density of energetic azole‐based compounds and their molecular structure is investigated through quantitative structure‐property relationship (QSPR) approach. The methodology of this work introduces a new model, which related density of azole‐based energetic compounds to the optimum elemental composition, the degree of unsaturation (DoU) of the compounds, presence of nitroimino group in the structural formula, as well as several non‐additive structural parameters. The presence of nitroimino functional group and also increasing the value of n_O/n_N in the formula of these compounds can enhance their density. The correlation is derived on the basis of experimental density values of 100 azole‐based energetic compounds with different molecular structure as training set. The determination coefficient of the new correlation is 0.923. Also, it has the root mean square deviation (RMSD) and the average absolute deviation (AAD) of 0.038 and 0.030 g · cm^–3, respectively. In addition, the correlation gives good predictions for further 25 azole‐based energetic compounds as test set (Q²_EXT = 0.901). The predictive ability of the correlation is checked using a cross validation method (Q²_LMO = 0.918). The proposed method can also apply for designing novel azole‐based energetic compounds.     

Physicochemical Properties and Surface Tension Prediction of Mixed Surfactant Systems: Triton X‐100 with Dodecylpyridinium Bromide and Triton X‐100 with Sodium Dodecylsulfonate

Dependences of the surface tension of aqueous solutions of ionic (dodecylpyridinium bromide, sodium dodecylsulfonate) and nonionic (Triton X‐100) surfactants and their mixtures on total surfactant concentration and solution composition were studied, and the surface tension of the mixed systems were predicted using different Miller's model. It was found that how to select the model for calculation of ω is corresponding to the degree of the deviation from the ideality during the adsorption of mixed surfactants. The compositions of micelles and adsorption layers at air‐solution interface as well as parameters (β^m, β^ads) of headgroup‐headgroup interaction between the molecules of ionic and nonionic surfactants were calculated based on Rubingh model. The parameters (B₁) of chain‐chain interaction between the molecules of ionic and nonionic surfactants were calculated based on Maeda model. The free energy of micellization calculated from the phase separation model (ΔG ₂ ^m ), and by Maeda's method (ΔG ₁ ^m ) agree reasonably well at high content of nonionic surfactant. The excess free energy ΔG _ads ^E and ΔG _m ^E (except α=0.4) for TX‐100/SDSn system are more negative than that TX‐100/DDPB system. These can be probably explained with the EO groups of TX‐100 surfactant carrying partial positive charge.