Solution properties of mixed surfactant system sodium dodecyl sulfate and alkyl polyoxyethylene ether system

The effect of oxyethylene groups in a nonionic surfactant on the solution properties of anionicnonionic systems is described; these systems are sodium dodecyl sulfate (SDS)—hexadecyl polyoxyethylene ethers (C₁₆POE_n, where n=10, 20, 30 and 40). The degree of ionic dissociation of the mixed micelles decreases with increasing numbers of oxyethylene groups in the nonionic surfactant. As polyoxyethylene chain lengths increase, the electrical conductivities of the mixed surfactant solutions decrease, in spite of the decrease in activation energy for conduction. The radius of the mixed micelle with the electric double layer is larger for a nonionic surfactant having a shorter polyoxyethylene chain length than for one having a long polyoxyethylene chain. This may be attributed to the fact that the mixed micelle is formed more easily by a nonionic surfactant with a shorter polyoxyethylene chain length than by one with a longer chain.     

Nonionic surfactant mixtures in an imidazolium-type room-temperature ionic liquid

The physicochemical properties of nonionic surfactant mixtures in an aprotic, imidazolium-type room-temperature ionic liquid (RT-IL) have been studied using a combination of static surface tensiometry, dynamic light scattering (DLS), and cryogenic transmission electron microscopy (cryo-TEM). The surfactants used in this study are phytosterol ethoxylates (BPS-n, where n is an oxyethylene chain length of either 5 or 30) and the selected RT-IL is 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF(6)). The shorter chain oxyethylene surfactant (BPS-5) exhibits greater surface activity in BmimPF(6) than BPS-30; hence, BPS-5 is a major component in driving the interfacial adsorption and molecular aggregation of the mixed system. The surface tension data demonstrate that an increased mole fraction of BPS-5 results in a decreased critical aggregation concentration (cac) and negatively increased Gibbs free energies estimated for molecular aggregation (ΔG(0)(agg)) and interfacial adsorption (ΔG(0)(ads)). Indeed, the compositions of the monolayer adsorbed at the air/solution interface and the molecular aggregate formed in the bulk solution are enriched with BPS-5. The combination of the DLS and cryo-TEM results demonstrates the spontaneous formation of multi-lamellar vesicles resulting from the BPS-5-rich composition of the molecular aggregates.     

Phase Behavior of Glycerol Trioleate‐Based Ionic Liquid Microemulsions

Glycerol trioleate‐based ionic liquid microemulsions are promising biolubricant alternatives. This study presents the formation and the phase behavior of glycerol trioleate‐based ionic liquid microemulsions. Areas of the single‐phase domain were calculated to illustrate the phase‐forming capacities of the designed systems. The effects of ionic liquid anions and cations, oxyethylene groups’ number of surfactant, mass ratio of surfactant to co‐surfactant, chain length of co‐surfactant, and temperature on the phase behavior and phase‐forming capacities of glycerol trioleate‐based ionic liquid microemulsions were investigated using pseudo‐ternary phase diagrams. The results showed that the phase‐forming capacities of glycerol trioleate‐based ionic liquid microemulsions with different ionic liquids were Tf₂N^?‐based > PF₆^?‐based > BF₄^?‐based, OMIM⁺‐based > HMIM⁺‐based > BMIM⁺‐based > EMIM⁺‐based. The designed systems contained ionic liquid‐glycerol trioleate amphiphilic balance; thus, glycerol trioleate‐surfactant micelles achieved the maximum solubilization capacity for the ionic liquid when the surfactant had approximately five oxyethylene groups with a surfactant to co‐surfactant mass ratio of 4:1. Moreover, increasing the temperature and the aliphatic chain length of co‐surfactant from C2 to C6 enhanced the ability of glycerol trioleate and ionic liquids to form microemulsions.     

OPEO表面活性剂在油水界面的分子动力学模拟

辛基酚聚氧乙烯醚(OPEO)是常用的非离子型表面活性剂,可以显著降低油水体系的界面张力。选择醋酸乙烯酯/水体系,通过改变OPEO中氧乙烯基的数量,采用MS7.0软件中的分子动力学(MD)模拟方法,在常温常压下对油/表面活性剂/水体系的界面生成能、界面厚度等指标进行测定,结果表明,氧乙烯基数量为12时,OPEO的界面生成能较高,降低醋酸乙烯酯/水体系界面张力的能力较好。     

Formation of a liquid crystalline phase between aqueous surfactant solutions and oily substances

The process in which a ternary liquid crystalline (LC) phase containing surfactant, water and oily substance is formed after contact of aqueous surfactant solution and oily substance was investigated by a combination of (i) microscopic observation in polarized light and (ii) penetration of water-soluble or oil-soluble dye into LC phase. The structure of LC phase and the process of its formation were found to be affected by many factors, such as kinds of surfactant, surfactant concentration, alkyl chain length of oil and so on. Oil is supposed to be gradually incorporated into LC phase with time. The fact that parts of LC phase are projected into the exterior surfactant solution, and that the continuous phase within LC phase is water, suggest the possibility of the dispersion of LC phase into the exterior solution. The process of the formation of LC phase implies some contribution to oily dirt removal. The process of the formation of LC phase implies some contribution to oily dirt removal.     

磺基甜菜碱型两性离子表面活性剂的相行为研究

采用自制的4种磺基甜菜碱,运用多种方法对4种磺基甜菜碱/短链醇/正癸烷/NaCl/水形成的微乳液体系相行为进行了研究,并考察了温度、磺基甜菜碱的分子结构、短链醇浓度及其分子结构等对微乳液相行为的影响。实验表明:温度越高,中相微乳液形成的中相体积越大;SB9体系形成中相微乳液时,所需要的最小w(醇)为2%,最大醇宽为12%;SB12体系形成中相微乳液时所需要的最小w(醇)为4%,最大醇宽8%;随着磺基甜菜碱烷基碳数的增加,微乳区面积增大,增溶能力降低;最佳增容参数SP*和表面活性剂在油相和水相的平均溶解度SO.W均随短链醇碳链的增加而增加;平衡界面膜上的表面活性剂和醇在整个微乳液体系中所占的质量分数C S,C A,短链醇平衡界面膜所占的质量比AS,短链醇在油水相中的平均溶解度AO.W,均随短链醇碳链的增加而减小;w(醇)的增加使得微乳液体系发生由WinsorⅠ→WinsorⅢ→WinsorⅡ型的相态变化。     

Effect of addition of alkali metal salts in hydrothermal synthesis and post heat-treatment on porosity of SBA-15

SBA-15 was hydrothermally synthesized at 80 °C for 48 h, and then the surfactant template for mesopore formation was removed by extraction with ethanol, washing with nitric acid, and heating at 200 °C. Addition of alkali metal chlorides to a synthesis gel of SBA-15 increased its mesopore diameter in the following order: no added salt < LiCl < KCl < CsCl. The micropore volume did not change with the addition of any alkali metal and was around 0.17 mL g^–1. These results suggest that alkali metal salt is inside the mesopore with a micelle template. When a small amount of potassium chloride was impregnated in SBA-15 after extraction and washing, micropore volume reduced almost to zero with heating at 400 °C in dry air, and the mesopore diameter and pore wall thickness were reduced by a larger amount than for non-impregnated SBA-15. It is likely that the micropores in the mesopore wall vanish due to condensation of silanols and/or reconstruction of siloxane bonds on the micropore wall, which are catalyzed by alkali metal halides.     

城市固体有机废弃物制备中孔活性炭

研究了以锯木屑、纸张、塑料的热解物(分别简称木炭、纸炭、塑料热解物)为原料制备中孔活性炭时孔结构发展的影响因素. 结果表明：当塑料热解物含量一定时，木炭、纸炭组成比的改变主要对活性炭的微孔产生影响，即二者的组成比越高，活性炭的微孔孔容越大；塑料热解物含量是活性炭中孔形成的主要影响因素，随着塑料热解物含量的增加，活性炭的中孔孔容先增加再减少；低的热解温度有利于活性炭中孔结构的形成和发展；最后对中孔形成的机理进行了探讨.     

Effects of organic templates on the structural properties of porous clay heterostructures: a non-micellar template model for porous structure

In this study, a series of surfactants with different chain lengths were used to investigate the effect of organic templates on the structural properties of porous clay heterostructures (PCH). The variation tendencies of structural properties and chemical component were characterized by X-ray diffraction, CHN elemental analysis, major element analysis, and nitrogen adsorption/desorption at ?196 °C. Non-local density functional theory was employed to characterize pore size distributions in both micropore and mesopore regions owing to the bi-model pore structures of PCH. The major textural parameters of PCH samples increased with increasing the chain length and the intercalated amount of template agent, while the most probable pore size remained unchanged around 1.3–1.4 nm. Based on the structural and chemical component results of PCH, a non-micellar template model was presented to explain the formation mechanism of porous structure. By the extrusion and occupation of polymerizate of TEOS within interlayer, a fixed number of hydrocarbon chains congregate together to form surfactant aggregates (template). The aggregates with different chain lengths cause the increase of pore volume in depth dimension rather than in diameter. The obtained results also shed some light on the different roles of inorganic base clay and organic template agents in the formation of porous structure. Montmorillonite as the inorganic host supplies the space for pillaring reaction and controls the arrangement of template agent within interlayer. As the template agent and modifying agent, the cationic surfactant is the dominant factor in forming pores relative to amine. The neutral amine mainly serves as catalyst for the polymerization of TEOS besides its co-template effect.     

具有介孔结构丝光沸石的合成与表征

基于丝光沸石骨架结构固有的晶体缺陷特征,提出诱导晶体结构缺陷和由结构缺陷衍生晶内介孔的研究方案。采用三元有机超分子胶束模板剂和两段变温晶化水热法,制备出丝光沸石基多级介孔材料。通过粉末X射线衍射、77K氮吸附–脱附、场发射透射电子显微镜、氨程序升温脱附对合成的介孔材料的晶相、形貌、介孔特征和水热稳定性进行了表征。结果表明：所合成的典型丝光沸石具有较高的相对结晶度,介孔比表面积和介孔体积分别为152.7m2/g和0.163 cm3/g;晶体内介孔在3～50 nm区间呈多级分布;其酸性质与微孔丝光沸石相匹配;水热稳定性较有序介孔材料MCM-41有显著提高。与聚集态纳米沸石组装介孔材料不同,合成的介孔丝光沸石晶体表面上介孔排布密度和尺寸分布缺乏均一性,故而由体相结构缺陷诱导形成的附加介孔呈显著无序状态。     

新型混合反胶团萃取溶菌酶的平衡行为

研究了由阴离子表面活性剂二-(2-乙基己基)琥珀酸酯磺酸钠(AOT)和非离子表面活性剂聚氧乙烯基(聚合度为4)壬基酚醚(OPE4)组成的一种新型混合反胶团体系及其萃取溶菌酶的平衡行为. 结果表明,该反胶团体系具有较大的含水量,且其含水量在较大的表面活性剂配比(0~0.8)范围内维持恒定,是由静电作用和胶束形态改变共同作用的结果. 无机盐种类和离子强度对上述混合反胶团的含水量有着显著的影响,继而影响到溶菌酶的萃取率. 它可归结为盐离子对扩散双电层和水化膜斥力的因素所致. 降低pH和提高总表面活性剂浓度均有利于溶菌酶的萃取.     

Mechanism of antifoam behavior of solutions of nonionic surfactants above the cloud point

Aqueous solutions of nonionic surfactants exhibit low foaming above their cloud point, a temperature above which the homogeneous solutions separates into two phases: a dilute phase containing a low surfactant concentration and coacervate phase containing a very high surfactant concentration (e.g., 20 wt% surfactant). In this work, foam formation was measured for the dilute phase, the coacervate, and the mixed solution using the Ross-Miles method for nonylphenol polyethoxylates with 8, 9, or 10 ethylene oxide moieties per molecule. The dilute phase showed no antifoam effect above the cloud point if the coacervate phase was not present, and the coacervate phase foamed little in the absence of the dilute phase. The coacervate phase acts as an oil droplet antifoam to the dilute phase. From surface and interfacial tension data, entering, spreading, and bridging coefficients for this system make it appear probable that the coacervate phase is forming bridges across the film lamellae of the dilute-phase foam and acting to suppress foam formation through the bridging mechanism.     

Mesogen-jacketed liquid crystalline polymers substituted with oligo(oxyethylene) as peripheral chain

Mesogen-jacketed liquid crystalline polymer (MJLCP) is a typical rod-shaped macromolecule. Its unique molecular architecture allows one to tune the geometric parameters of the macromolecular rod. Moreover, the rod surface chemistry can be controlled by designing the peripheral groups of the lateral mesogens. In previous work in this system, short alkyl chains have been used and the resultant macromolecular rods therefore have a hydrophobic surface. In this paper, we report using oligo(oxyethylene) groups as the peripheral groups of the lateral mesogens. Poly{{2,5-bis[4-methoxyoligo(oxyethylene)phenyl]oxycarbonyl}styene} (PnEOPCS) with different oligo(oxyethylene) chain length has been synthesized. These oligo(oxyethylene) groups led to macromolecular rods with hydrophilic surface. Differential scanning calorimetry, polarized light microscopy, and one-/two-dimensional wide-angle X-ray diffraction experiments were carried out to study the phase structures and phase behaviors of this series of polymer. The existence of flexible polar groups lowered the glass transition temperatures of PnEOPCS. All polymers studied showed supramolecular columnar nematic or hexatic columnar nematic phase, which arose from the parallel alignment of the polymer supramolecular rods. The diameter of the cylindrical building block increased with increasing the length of the oligo(oxyethylene) groups. The macromolecular rod surface can be further tuned by complexation the oligo(oxyethylene) with lithium salts. Detailed study showed that this complexation also tremendously affected the liquid crystalline phase of the polymer.     

Surface and Lateral Interactions of Nonylphenol Nonionic Surfactants with Porous Resin

The adsorption process between porous resins with different surface properties and nonylphenol non-ionic surfactants of the same hydrocarbon chain length but varying oxyethylene units was investigated. The adsorption of NPEOn with shorter EO chains is greater than those with longer EO chains on the surfaces of resins, and the strength of the adsorption was affected by resin surface-surfactant and surfactant-surfactant lateral interactions. Lateral interactions are endothermic, and contribute more to the adsorption process on aminated resins (MN-100, MN-150) than on hyper-crosslinked resins (MN-200, NDA-150). The surface interactions are mainly due to bonding between the hydrophobic moiety of the surfactant and hydrophobic surfaces of the resins without electrical interaction or hydrogen bonding, even on aminated resins (MN-100, MN-150). Positive ΔH values indicate that the adsorption process is endothermic overall, which is supported by the increase in adsorption capacity observed with increasing temperature.     

Fatty amide ethoxylates: Synthesis and self-assembly

A series of fatty acid monoethanolamide ethoxylates was synthesized. Tensiometry and fluorescence were used to study the solution behavior of this surfactant series. The effec of the amide bond, the effect of unsaturations in the hydrocarbon chains, and the effects of the oxyethylene chain length were investigated. The presence of the amide group was found to lead to a decrease in the critical micelle concentration (CMC), an effect that is probably due to the formation of hydrogen bonds between neighboring molecules. The surface tension at the CMC was higher when an amide bond was present in the surfactant. This probably reflects the increase in size of the polar group (decrease in the critical packing parameter value) which is unfavorable for close alignment of surfactant molecules at the air-water interface. The presence of unsaturations in the hydrophobic tail gave an increase in the CMC. This may partly be due to the surfactants becoming more hydrophilic and partly to the increased bulkiness of the chains, rendering packing into closed aggregates and formation of hydrogen bonds between amide groups more difficult. The cross-sectional headgroup areas of the surfactants increased with the degree of unsaturation as a consequence of more unfavorable packing at the surface.     

The role of surfactant structure and monoethanolamine in the environmental stress cracking of polycarbonate

The critical strains required to initiate cracking of polycarbonate exposed to a number of poly(oxyethylene)ethoxylate surfactants were determined. Solubility parameters of the surfactants were calculated from knowledge of the molecular structure. A model proposed by Jacques and Wyzgoski that uses the square of the solubility parameter difference of the surfactant and polycarbonate and the surfactant molar volume was determined to be useful for predicting critical strains for polycarbonate. A major assumption in this model is that stress cracking is related to swelling or plasticization of the polymer by the cracking agent, which ultimately leads to the polymer's failure. However, the model does not predict the observed strong stress cracking of polycarbonate by monoethanolamine. In this investigation it was determined that polycarbonate is chemically degraded by monoethanolamine. This degradation is sufficient to initiate stress cracking at lower strains than would otherwise be predicted by solubility parameter and molar volume concepts. With the knowledge obtained from this investigation, it is possible to predict which poly(oxyethylene)ethoxylate surfactants are stress cracking agents for polycarbonate.     

Effect of excess silicate on the structure formation and textural properties of MTS materials

The synthesis of micellar templated silica (MTS) materials has been conducted with different SiO₂/CTAB molar ratios for two different cetyltrimethylammoniumbromide (CTAB) concentrations of 0.02 and 0.07 M to examine the structure formation for cubic (SBA-1) as well as for hexagonal (SBA-3) surfactant arrangement in acidic reaction medium with increasing silicate excess. Reaction products were analyzed with X-ray diffraction, N₂ physisorption and TG-MS. It was found that an increase of the silicate concentration leads to the formation of additional silica gel in the resulting MTS material, which causes not only a decrease of specific surface area and pore volume, but also of the mesopore diameter. The latter effect is explained by a proposed embedding theory. Furthermore, with increasing silicate content in the synthesis mixture a phase transformation from hexagonal to cubic pore arrangement was found for the CTAB concentration of 0.07 M and the maximum SiO₂/CTAB molar ratio for ordered pore arrangement has been determined.     

Nonionic polymeric surfactant template for mesoporous NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> formation

Mesostructured NiCo₂O₄ is synthesized in presence of nonionic glucose based polymeric surfactant, β-C₁₀Alkyl Poly Glucoside (β-C₁₀APG). Formed NiCo₂O₄ mesostructures have pore size in the range of 25–65 Å and surface area of 202.9 m²/g. Formed particles are rod shape with 2d hexagonal pattern and Fd3m space group point symmetry. The formation of mesostructure phase is explained by coordination bond formation between metal ions with surfactant head. β-C₁₀APG has the potential to be explored as green template for mesopore formation.     

Synergism and Phase Behavior of Alcohol Polyoxyethylene Ether Acetate and Cationic Surfactant-Mixed Systems

Synergism in mixed micelle formation and surface tension reduction efficiency and the ternary phase behavior of anionic surfactant (alcohol polyoxyethylene ether acetate containing 10 ethylene oxide group and a fatty chain of C_16–18) with cationic surfactants (dodecyldimethylbenzyl ammonium chloride and lauryltrimethyl ammonium chloride) were investigated. Surface tension of the systems at different molar ratios was studied in detail and the interaction parameters of each system were calculated. The results show that both systems have lower values of critical micelle concentration (CMC) and γ_cmc than individual surfactants especially at equal ratio between cationic and anionic surfactants. Both systems present synergism in mixed micelle formation and surface tension reduction efficiency. The ternary phase behavior of the two systems was investigated using a polarized microscope. The micellar phase and lamellar phase were observed in both systems and the coexisting phase was only observed in the dodecyldimethylbenzyl ammonium chloride system.     

Preparation of structured meso–macroporous silica materials: influence of composition variables on material characteristics

Meso–macroporous silica materials with a well-ordered array of mesopores were prepared from oil-in-water emulsions. The influence of the following three composition variables on material characteristics was studied: the dispersed phase fraction of the emulsion, the concentration of silica used and the concentration of surfactant. The obtained materials were characterized via small-angle X-ray diffraction scattering, scanning electron microscopy, transmission electron microscopy, Hg intrusion porosimetry and nitrogen adsorption–desorption isotherms. A network of structured mesopores was obtained even when using a highly concentrated emulsion (volume of the disperse phase, ? ≥ 0.75). The mesopores network presented a hexagonal arrangement, with mesopore diameters between 4 and 7 nm. Non-ordered macropores, with diameters between 50 nm and 10–15 μm were also present, depending on composition variables. The isotherms were of type IV, typical of mesoporous materials, but at high p/p₀ they were the usual shape for the macroporous materials. The possibility of tailoring mesopore and macropore structures by altering in composition variables could extend the application of these materials.