Nanoscopic microheterogeneities or pseudo-phase separations in non-conventional liquids

This article discusses new concepts in macroscopically monophasic colloidal systems, where entropy is a major driving force for very subtle interactions and structuring. First, we show how microemulsion-similar structures can be achieved with hydrotropes. These aggregates are less defined in structure and of shorter lifetime than classical micelles but still potentially useful microheterogeneities with internal interfaces. The other extreme case of strong interactions is given when cationic and anionic surfactants are mixed in equimolar ratios. It is well known that surfactants can be made more soluble when ethylene oxide groups are incorporated. This strategy is applied for such ‘catanionics’ to avoid surfactant precipitation. Finally, we consider the fact that ethylene oxide groups increase the size of the hydrophilic headgroups of carboxylates so that the geometrical constraints compel a direct spherical shape even in the absence of water. As a result, ‘water-free direct microemulsions’ with only charged surfactants and oil are conceivable.     

Synthesis of poly(n‐butyl acrylate) homopolymer and poly(styrene‐b‐n‐butyl acrylate‐b‐styrene) triblock copolymer via AGET emulsion ATRP using a cationic surfactant

Cationic emulsions of triblock copolymer particles comprising a poly(n‐butyl acrylate) (PⁿBA) central block and polystyrene (PS) outer blocks were synthesized by activator generated by electron transfer (AGET) atom transfer radical polymerization (ATRP). Difunctional ATRP initiator, ethylene bis(2‐bromoisobutyrate) (EBBiB), was used as initiator to synthesize the ABA type poly(styrene‐b‐n‐butyl acrylate‐b‐styrene) (PS‐PⁿBA‐PS) triblock copolymer. The effects of ligand and cationic surfactant on polymerizations were also discussed. Gel permeation chromatography (GPC) was used to characterize the molecular weight (M_n) and molecular weight distribution (MWD) of the resultant triblock copolymers. Particle size and particle size distribution of resulted latexes were characterized by dynamic light scattering (DLS). The resultant latexes showed good colloidal stability with average particle size around 100–300 nm in diameter. Glass transition temperature (T_g) of copolymers was studied by differential scanning calorimetry (DSC). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 611–620     

Smart Soft‐Templating Synthesis of Hollow Mesoporous Bioactive Glass Spheres

Hollow bioactive glass spheres with mesoporous shells were prepared by using dual soft templates, a diblock co‐polymer poly(styrene‐b‐acrylic acid) (PS‐b‐PAA) and a cationic surfactant cetyltrimethylammonium bromide (CTAB). Hollow mesoporous bioactive glass (HMBG) spheres comprise the large hollow interior with vertical mesochannels in shell, which realize large uptake of drugs and their sustained release. The formation of hydroxyapatite layer on the surface of HMBG particles shows the clear evidence for promising application in bone regeneration.     

Morphological and Interaction Characteristics of Surface-Active Ionic Liquids and Palmitic Acid in Mixed Monolayers

A series of water soluble, surface-active ionic liquids (SAILs), namely, 1-alkyl-3-methyl imidazolium chlorides ([C_n-mim]Cl) and their mixtures with palmitic acid (PA) are investigated in Langmuir monolayers and Langmuir–Blodgett films. It is inferred from the surface pressure-area isotherms that C₁₆-mim-IL mixes non-ideally with PA and stabilizes the binary mixed films. In addition, the residence of mim-IL at the water surface is enhanced as a function of the increasing alkyl side chain length. Generally, the compressional moduli values decrease upon increasing the content of the mim-ILs over a wide range of compositions. Furthermore, film relaxation measurements indicate that the IL component is selectively excluded from the mixed films upon achieving a certain target pressure. Brewster angle microscope images demonstrate minimal changes on the PA domains in the presence of either C₄- and C₈-mim-ILs, whereas presence of the hexadecyl counterpart results in the formation of condensed sheets. Atomic force microscopy imaging of deposited films show the formation of propeller-like aggregates when C₈- or C₁₆-mim-IL is present in the mixed films.     

Spreading of Oil Droplets Containing Surfactants and Pesticides on Water Surface Based on the Marangoni Effect

Oil droplets containing surfactants and pesticides are expected to spread on a water surface, under the Marangoni effect, depending on the surfactant. Pesticides are transported into water through this phenomenon. A high-speed video camera was used to measure the movement of Marangoni ridges. Gas chromatography with an electron capture detector was used to analyze the concentration of the pesticide in water at different times. Oil droplets containing the surfactant and pesticide spread quickly on the water surface by Marangoni flow, forming an oil film and promoting emulsification of the oil–water interface, which enabled even transport of the pesticide into water, where it was then absorbed by weeds. Surfactants can decrease the surface tension of the water subphase after deposition, thereby enhancing the Marangoni effect in pesticide-containing oil droplets. The time and labor required for applying pesticides in rice fields can be greatly reduced by using the Marangoni effect to transport pesticides to the target.     

界面扩张流变法研究C12mimBr对Gemini12-2-12在空气/水界面聚集行为的影响

采用界面扩张流变技术研究了季铵盐偶联表面活性剂C₁₂-(CH₂)₂-C₁₂·2Br (Gemini12-2-12)及其与离子液体表面活性剂溴化1-十二烷基-3-甲基咪唑(C₁₂mimBr)复配体系的动态界面张力、扩张流变性质和界面弛豫过程等, 探讨了C₁₂mimBr 对C₁₂mimBr/Gemini12-2-12 混合体系界面性质的影响及C₁₂mimBr 对Gemini12-2-12界面聚集行为影响的机制. 结果表明, 随着离子液体表面活性剂的不断引入, 体系界面吸附达到平衡所需的时间逐渐缩短, 扩张模量和相角明显降低, 界面吸附膜由粘弹性膜转变为近似纯弹性膜; 同时, 界面及其附近的弛豫过程也发生显著变化, 慢弛豫过程消失, 快弛豫过程占主导地位, 且离子液体浓度越高, 快弛豫的贡献越大. 这些界面性质的变化主要归因于离子液体表面活性剂C₁₂mimBr参与界面形成及两表面活性剂在界面竞争吸附的结果. 少量离子液体表面活性剂C₁₂mimBr 的加入可以填补疏松的Gemini12-2-12 界面上的空位, 形成混合界面吸附膜. 随着C₁₂mimBr 含量的增加, 嵌入界面的C₁₂mimBr 分子数不断增多, 导致界面上相互缠绕的Gemini12-2-12烷基链“解缠”, 在体相和界面分子扩散交换的过程中“解缠”的Gemini12-2-12分子从界面上解吸回到体相, 与此同时, C₁₂mimBr 分子相对较小的空间位阻及较强的疏水作用促使其优先扩散至界面进而取代Gemini12-2-12分子, 最终界面几乎完全被C₁₂mimBr分子所占据.     

Liquid–liquid microextraction and spectrophotometric determination of anionic surfactants using Astra Phloxine FF

A novel and simple procedure for determination of anionic surfactants has been developed. The method is based on the reaction of sodium dodecyl sulphate (SDS) with Astra Phloxine FF reagent at pH 3–8, followed by liquid–liquid microextraction of the formed ion associate into an organic phase containing a mixture of carbon tetrachloride and dichloroethane (4:1, v/v) and subsequent UV-Vis detection at 555 nm. The calibration plot was linear in the range 0.006–0.29 mg L^?1 of SDS. The limit of detection (LOD), calculated based on 3s, is 0.002 mg L^?1. The method was applied to the determination of anionic surfactants in real wastewater samples.     

Fully printed flexible audio system on the basis of low‐voltage polymeric organic field effect transistors with three layer dielectric

Fully mass printed, flexible and truly polymeric organic field effect transistors consisting of a three layer dielectric made of CYTOP (low‐k), PVA (intermediate) and P(VDF‐TrFE‐CTFE)(high‐k) are introduced. Gravure‐, flexo‐and screen printing were selected as highly productive manufacturing technologies. These OFETs work at strongly reduced voltages and show high field effect mobility (µ = 0.2 cm²/Vs) and remarkable good bias stress stability at very high current density (50 µA/mm). Fully printed OFETs are used for the realization of ring oscillators working in the kHz regime at reduced supply voltage (10 V). In combination with printed fully polymeric piezoelectric loudspeakers, this work shows for the first time fully printed flexible audio systems. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1409–1415     

Synthesis and Design of Aggregation‐Induced Emission Surfactants: Direct Observation of Micelle Transitions and Microemulsion Droplets

The direct visualization of micelle transitions is a long‐standing challenge owing to the intractable aggregation‐caused quenching of light emission in the micelle solution. Herein, we report the synthesis of a surfactant with a tetraphenylethene (TPE) core and aggregation‐induced emission (AIE) characteristics. The transition processes of surfactant micelles and the microemulsion droplets (MEDs) formed by the surfactant with a TPE core were clearly visualized by a high‐contrast fluorescence imaging method. The fluorescence intensity of the MEDs decreased as the size of MEDs increased as a result of weakening of the restriction of intramolecular rotation (RIR). The results of this study deepen our understanding of micelle‐transition processes and provide solid evidence in favor of the hypothesis that the AIE phenomenon has its origin in the RIR of fluorophores in the aggregate state.     

Investigation of the surfactant type and concentration effect on the retention factors of glutathione and its analogues by micellar electrokinetic chromatography

In the present study, a micellar electrokinetic chromatographic method was used to determine the retention factors of hydrophilic monomeric and homodimeric forms of glutathione analogues. Ionic‐liquid‐based surfactant, 1‐tetradecyl‐3‐methylimidazolium chloride, as well as cetyltrimethylammonium bromide and phosphate buffer (pH 7.4) were employed in the experiments. Since the studied peptides possess a negative charge under physiological conditions, it is expected that the peptides interact with the oppositely charged 1‐tetradecyl‐3‐methylimidazolium chloride and cetyltrimethylammonium bromide micelles via hydrophobically assisted electrostatic forces. The dependence of the retention factor on the micellar concentration of 1‐tetradecyl‐3‐methylimidazolium chloride and cetyltrimethylammonium bromide is nonlinear and the obtained curves converge to a limiting value. The retention factor values of GSH analogues were in the range of 0.36–2.22 for glutathione analogues and –1.21 to 0.37 for glutathione when 1‐tetradecyl‐3‐methylimidazolium chloride was used. When cetyltrimethylammonium bromide was employed, the retention factor values were in the range of 0.27–2.17 for glutathione analogues and –1.22 to 0.06 for glutathione. If sodium dodecyl sulfate was used, the retention factor values of glutathione analogues with carnosine moiety were in the range of –1.54 to 0.38.