Surfactant Chain Research Articles

‘On and Off’ intercalative binding behaviour of double chain surfactant cobalt(III) complex containing 2, 2′-bipyridyl ligand in β-Cyclodextrin: A detail approach on Host-guest inclusion of surfactant cobalt(III) complex and CT-DNA binding in micro-heterogeneous medium

The binding interaction of surfactant cobalt(III) complex, cis-[Co(bpy)2(HA)2](ClO4)3, in which bpy is 2,2-bipyridine and HA is hexadecylamine or cetylamnine with DNA was through intercalative mode via the long aliphatic chains present in the ligands. The binding was investigated by various techniques, electronic absorption, fluorescence spectroscopy, circular dichroism (CD), cyclic voltametry (CV) and viscosimetry measurements. The spectroscopic studies together with cyclic voltammetry and viscosity experiments support that the surfactant cobalt(III) complex binds to calf thymus DNA by intercalation through the aliphatic chain present in the complex into the base pairs of DNA. The presence of bipyridine ligand with larger π-frame work may also enhance intercalation. UV–vis., spectrum showed 4 nm bathochromic shift of the absorption band at 352 nm along with significant hypochromicity for the absorption band of the complex. The intrinsic binding constants(at below and above CMC are Kb = 2.41 × 105M−1, Kb = 3.12 × 106M−1 respectively) is more in keeping with intercalators and suggests this binding mode. The viscosity measurements showed that the surfactant cobalt(III) complex-DNA interaction can be hydrophobic and confirm intercalation. Moreover, the complex induced detectable changes in the CD spectrum of CT-DNA. Competitive binding study with ethidium bromide (EB) shows that the surfactant complex exhibits the ability to displace the DNA-bound EB indicating that the complex binds to DNA in strong competition with EB for the intercalative binding site. Also, CV results confirm this mode because, with increasing the CT-DNA concentration, shift to higher potential was observed. Besides the effect of binding of surfactant cobalt(III) complex to DNA in presence of β-cyclodextrin has also studied. This binding of the surfactant cobalt(III) complex in presence of β-cyclodextrin medium has been prevented (at below and above CMC are Kb = 5.45 × 104M−1, Kb = 6.92 × 105M−1 respectively) due to the incorporation of the aliphatic chains into the cavity of β-cyclodextrin. In presence of β-cyclodextrin the binding occur through surface and (or) groove binding can be attributed to the inclusion of the long aliphatic chain that is present in one of the ligands into cyclodextrin.

Drop shape stability vs shape shifting: Role of surfactant adsorption layer

Emulsion droplets, composed of long linear molecules (e.g. n-alkanes) and stabilized by long chain surfactants, can spontaneously change their shape upon cooling and morph from spheres into regular polyhedra, polygonal platelets, rods and thin fibers. Until now, these dynamic shape changes have been studied upon continuous temperature decrease. Therefore, it had remained unclear whether the observed shapes were stable or they appeared as intermediate states during the transformation of the initial sphere into some final shape(s). In the current study, we performed dedicated experiments at fixed temperature to distinguish between the stable, metastable and unstable shapes and to define the factors which affect the kinetics of the observed transitions. The results showed that the stable shapes are equilateral triangular platelets (in all surfactant solutions) and the rod-like particles, when stabilized by surfactants with narrow compositional variations. The distorted octahedrons (seen as hexagonal platelets in transmitted light) were metastable and preserved their shape for many minutes. The other shapes, e.g. the flat hexagonal and tetragonal platelets, were unstable and continued to transform until they reached one of the stable states or alternatively – until they formed spheroidal droplets extruding thin fibers from their bodies. These experimental results are in general agreement with the theoretical model developed by Haas et al. (Phys. Rev. Lett. 2017, Phys. Rev. Res. 2019). The rate of shape transformations increased with the level of subcooling and/or with the decrease of drop size.

Effect of Surfactant Chain Length on Emulsification Dynamics of Self Emulsifying Formulation of Poorly Soluble Drug.

In this work, the aim was to study the effect of the chain length of surfactant on the self emulsifying system of a poorly soluble drug, aceclofenac. The selection of almond oil as a lipid vehicle was done on the basis of solubility and compatibility of the vehicle with the drug. The effect of varying chain length of different surfactants of Tween series, namely Tween 20, Tween 40, Tween 60 and Tween 80, was evaluated on self emulsifying efficiency by constructing the pseudoternary diagrams. PEG-400 was used as a co-surfactant in a definite ratio with all the surfactants to minimize their concentration. The best self emulsifying ability was exhibited by Tween 80: PEG-400 combination followed by Tween 60: PEG-400, Tween 40: PEG-400, Tween 20: PEG-400. This observation indicates that as the chain length of Tweens increases, their ability to form a good microemulsion increases if the same co-surfactant is used. However, it has also been found that the presence of unsaturated bond in Tween 80 provides it an elasticity which supports good intermixing of oil and water, leading to formation of a fine microemulsion. Six different formulations were prepared using a combination of almond oil, Tween 80, PEG-400 and the drug aceclofenac. The formulations were subjected to various evaluation parameters, such as dispersibility, transmittance, pH, globule size, polydispersibility, zeta potential, viscosity, refractive index and in vitro dissolution. The best formulation was found to have globule size of less than 100 nm and zeta potential of -3.35 ± 0.60 mV, indicating the formation of a microemulsion of aceclofenac with good stability.

Promoting the utilization efficiency of agrochemicals via short-chain nonionic fluorinated synergist: Strategies and working mechanisms

Wastage of agrochemicals results in considerable environmental pollution and economic loss. The use of trisiloxane surfactants as synergists has proven to allow for reduction in agrochemical application rates, but these surfactants show poor resistance to hydrolysis, which can attenuate their synergistic effects. Herein we report the development of a short-chain nonionic fluorinated surfactant, designated mPEG200-TEOH-6, as a novel agrochemical synergist. In contrast to conventional long-fluorocarbon chain surfactants, our short-chain fluorinated surfactant can avoid the risk of persistence and bioaccumulation in the environment. We determined the thermal storage stability of mPEG200-TEOH-6 and investigated its effects on the static surface tension, dynamic surface tension, contact angle, and thermal storage stability of four agrochemicals solutions, which explained its synergistic efficacy. In addition, we compared its effects with those of the commercial surfactant Silwet 408. Both mPEG200-TEOH-6 and Silwet 408 clearly improved the utilization efficiency of the agrochemicals, but mPEG200-TEOH-6 displayed substantially greater synergistic efficiency than Silwet 408; specifically, the former markedly decreased the static surface tension of agrochemical solutions, increased their diffusivity and wettability, and decreased their LC50 values. Strikingly, we found that mPEG200-TEOH-6 was more stable than Silwet 408 under thermal storage conditions. The result presented herein can be used to guide the use of surfactants and agrochemicals in agriculture.

Fabrication of organobentonite by microwave‐assisted heating and its adsorption property for phenol

AbstractBACKGROUNDThe adsorption removal of phenol onto bentonite that was prepared by the traditional hydrothermal method has been widely studied; especially, surfactant‐modified bentonite has achieved an exclusive position on effective removal to phenol. However, the adsorption performance of the bentonite functionalized by double‐carbon chain surfactants in a microwave field for phenol is relatively low. The study on the fabrication of organobentonite by microwave‐assistance to remove organic pollutants still needs to be investigated.RESULTSThe adsorption performance of bentonite was enhanced after functionalizing with Dihexadecyldimethylammonium Bromide (D1621). FTIR and XRD patterns revealed that D1621 was successfully intercalated into bentonite, and the interval space was increased by 1.54 to 1.84 nm. The optimized preparation condition was obtained at a molar ratio (D1621: Bentonite) of 0.36, solid–liquid ratio (D1621 + Bent: water) of 0.12, microwave mode of Med, and thermal radiation for 6 min based on the indicator of phenol adsorption uptake. An excellent removal rate for phenol was observed at pH 2 to 7 and room temperature in adsorption tests. The adsorption process was spontaneous at room temperature according to thermodynamic parameters, and it agrees with Freundlich (R2 = 0.9781) and pseudo‐second‐order (R2 = 0.9999) models, validating a chemisorption process.CONCLUSIONThe D1621‐Bent perpetrated by using the microwave‐assisted heating method was proven to be a reliable adsorbent for phenol in water. The adsorption performance of bentonite on phenol was remarkably enhanced after the introduction of organic modifiers. © 2022 Society of Chemical Industry (SCI).

Mixed-surfactant perovskites with enhanced photostability

Blue and green emitting methylammonium lead bromide perovskite particles with improved UV-light stability have been developed by tuning structure and stabilization with a mixture of different single- and double-tailed surfactants. The ratio of the long alkyl chain surfactants to the methyl ammonium bromide allows for tailoring of the emission color of ready to use perovskite particles without further purification processes. The combination of single and double tailed surfactants exceeds the properties and geometries of the perovskite particles obtainable with a single surfactant. With a mixture of octylammonium bromide and dimethyldioctadecyl bromide, the perovskite particles show a highly anisotropic shape with a layered pyramid structure. The effect of surfactant composition on the perovskite particles’ structure, morphology and light-emitting properties has been elucidated. As these mixed surfactant perovskites are more robust against UV-light than other perovskite particles, they bear great potential for applications in optical devices such as LEDs.

Promoting the removal of fine particles by surfactants in a novel cyclone with heterogeneous-condensation agglomeration: A combined experimental and molecular dynamics study

Using heterogeneous-condensation agglomeration to enhance removal of fine particles by conventional equipment is an economical and efficient method. Recently proposed Cloud-Air-Purifying (CAP) technology, which combines heterogeneous-condensation agglomeration with a centrifugal field, has significantly improved the removal efficiency of fine particles in gas cyclones. In this work, surfactants were used to further enhance the removal of fine particles. The effect of three surfactants on promoting the removal of fine particles was investigated experimentally. The results indicated that non-ionic surfactant octylphenol polyoxyethylene ether (10) (OP-10) had the best effect on promoting the removal of methylated silica (SiO2-CH3) particles, because it improved heterogeneous condensation of fine particles and collision agglomeration between particles by improving the surface wettability, resulting in the formation of larger aggregates. Furthermore, the interaction energy, mean square displacement and hydrogen bond interactions in different simulation systems were calculated by molecular dynamics simulation to study the mechanism of surfactants on improving the surface wettability. The simulation results demonstrated the hydrophobic tail chains of OP-10 molecules spontaneously adsorbed on the nonpolar SiO2(001)–CH3 surface through the Van der Waals interaction, which changed the surface polarity and reduced the solid–liquid interaction energy. Meanwhile, hydrogen bonds were formed between polar head groups and water molecules, which enhanced the interaction between water molecules and the surface. Moreover, the mobility of water molecules is enhanced by surfactant molecules. The spatial distribution of the head group and tail chain of surfactant is an important factor affecting the surface wettability. This work is of great importance for enhancing the removal of fine particles in the dedusting system with heterogeneous-condensation agglomeration technology.

Influence of micellar size on the structure of surfactant-DNA complexes.

We have studied the structure of complexes of the cationic surfactant dodecyltrimethylammonium bromide (DTAB) with DNA as a function of surfactant to DNA base molar ratio (R) and salt concentration. Small-angle x-ray scattering data show the formation of nematic gels at lower and higher salt concentrations, irrespective of the value of R. Two crystalline phases are observed over intermediate salt concentrations; a square (S) phase for R>3 and a hexagonal (H_{S}) phase for lower R. Electron density maps of these phases show intercalated structures, with DTAB micelles sandwiched between long DNA strands. The composition of these complexes, estimated using elemental analysis, indicates that the micelles are not very long, and they occupy only about half of the interstitial volume between the DNA strands. This phase behavior is strikingly different from that of complexes of DNA with longer chain surfactants cetyltrimethylammonium bromide (CTAB) and tetradecyltrimethylammonium bromide (TTAB), which show only a hexagonal (H) phase over similar ranges of R and salt concentration, the H_{S} structure observed in the present study being a sqrt[3]×sqrt[3] superlattice of the H structure. Madelung energies of the S and H structures, calculated from the electrostatic interaction between their cylindrical constituents, suggest that the former is preferred in DTAB-DNA complexes due to the smaller micellar radius of DTAB. The propensity of DTAB to form short micelles seems also to favor the H_{S} phase at lower R. These results illustrate the important role of micellar size in determining the structure of these two-dimensional macro-ion crystals.

Self-assembly of Symmetric Double Chain Surfactants Derived from Internal Ketone in an Aqueous System

Self-assembly of Symmetric Double Chain Surfactants Derived from Internal Ketone in an Aqueous System

Digestion of lipid excipients and lipid-based nanocarriers by pancreatic lipase and pancreatin

The digestion behaviour of lipid-based nanocarriers (LNC) has a great impact on their oral drug delivery properties. In this study, various excipients including surfactants, glycerides and waxes, as well as various drug-delivery systems, namely self-emulsifying drug delivery systems (SEDDS), solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) were examined via the pH-stat lipolysis model. Lipolysis experiments with lipase and pancreatin revealed the highest release of fatty acids for medium chain glycerides, followed by long chain glycerides and surfactants. Waxes appeared to be poor substrates with a maximum digestion of up to 10% within 60 min. Within the group of surfactants, the enzymatic cleavage decreased in the following order: glycerol monostearate > polyoxyethylene (20) sorbitan monostearate > PEG-35 castor oil > sorbitan monostearate. After digestion experiments of the excipients, SEDDS, SLN and NLC with sizes between 30 and 300 nm were prepared. The size of almost all formulations was increasing during lipolysis and levelled off after approximately 15 min except for the SLN and NLC consisting of cetyl palmitate. SEDDS exceeded 6000 nm after some minutes and were almost completely hydrolysed by pancreatin. No significant difference was observed between comparable SLN and NLC but surfactant choice and selection of the lipid component had an impact on digestion. SLN and NLC with cetyl palmitate were only digested by 5% whereas particles with glyceryl distearate were decomposed by 40–80% within 60 min. Additionally, the digestion of the same SLN or NLC, only differing in the surfactant, was higher for SLN/NLC containing polyoxyethylene (20) sorbitan monostearate than PEG-35 castor oil. This observation might be explained by the higher PEG content of PEG-35 castor oil causing a more pronounced steric hindrance for the access of lipase. Generally, digestion experiments performed with pancreatin resulted in a higher digestion compared to lipase. According to these results, the digestion behaviour of LNC depends on both, the type of nanocarrier and on the excipients used for them.

Quatsomes Formulated with l-Prolinol-Derived Surfactants as Antibacterial Nanocarriers of (+)-Usnic Acid with Antioxidant Activity.

The efficacy of the treatment of bacterial infection is seriously reduced because of antibiotic resistance; thus, therapeutic solutions against drug-resistant microbes are necessary. Nanoparticle-based solutions are particularly promising for meeting this challenge because they can offer intrinsic antimicrobial activity and sustained drug release at the target site. Herein, we present a newly developed nanovesicle system of the quatsome family, composed of l-prolinol-derived surfactants and cholesterol, which has noticeable antibacterial activity even on Gram-negative strains, demonstrating great potential for the treatment of bacterial infections. We optimized the vesicle stability and antibacterial activity by tuning the surfactant chain length and headgroup charge (cationic or zwitterionic) and show that these quatsomes can furthermore serve as nanocarriers of pharmaceutical actives, demonstrated here by the encapsulation of (+)-usnic acid, a natural substance with many pharmacological properties.

Effect of an excess of surfactant on thermophoresis, mass diffusion and viscosity in an oily surfactant-stabilized ferrofluid.

The effect of an excess of surfactant on the thermophoresis of a sterically stabilized ferrofluid is investigated experimentally by forced Rayleigh scattering (FRS). The experiments are performed with a stable magnetic fluid sample to which controlled amounts of surfactant are added. A decrease in the thermally induced transport of magnetic nanoparticles is observed while increasing the temperature T. The positive Soret coefficient [Formula: see text] decreases by adding 2vol% of surfactant at room temperature. As shown by FRS relaxation, this decreasing is mainly associated with a reduction of the interaction between the carrier fluid and individual nanoparticles. No significant effect of extra surfactant on the sign of [Formula: see text] is observed at higher T's (up to [Formula: see text]C). Dynamic light scattering at room temperature reveals the presence of a small amount of clusters/aggregates in the samples, which are hardly detectable by FRS relaxation. The presence of these small clusters/aggregates is confirmed by a rheological probing of the fluid properties. Whatever T, a small amount of added surfactant first causes a decrease of the ferrofluid viscosity, associated with a 10% decreasing of the flow activation energy. Further on, viscosity and activation energy both recover at higher excess surfactant concentrations. These results are analyzed in terms of saturation of the surfactant layer, concentration of free surfactant chains and heat of transport of the nanoparticles.

Surfactant-assisted tuning of K2V3O8 nanorods for robust charge dynamics in semiconductor photocatalysis

This work presents a deep investigation into the structural and optoelectronic properties of K2V3O8 nanorods for testing their photocatalytic potentials. K2V3O8 nanorods have been synthesized by a simple surfactant-assisted hydrothermal method, with the surfactant SDS being incorporated to tune the morphology of the nanorods. Morphological analyses have revealed a profound effect of SDS in tailoring the morphology of the nanorods, due to a systematic layer by layer assembly of K2V3O8 nuclei along the surfactant chains. Various structural and optoelectronic analyses have been performed to establish the enhanced charge migration and charge separation efficiency along the smooth nanorod surfaces. The spectroscopic analyses have been theoretically studied by generating electronic structures via DFT calculations. The tuned nanorods demonstrated excellent photocatalytic activity, achieving 93% degradation of complex pharmaceutical levofloxacin and a robust photocurrent density of 0.7 mA/cm2 at 1.23 V vs RHE. Thus, this work establishes K2V3O8 nanorods as a novel material for photocatalysis and also explores their structure–property relationships for achieving optimal photocatalytic activity.

Gemini Surfactant Mediated Catansomes for Enhanced Singlet Oxygen Generation of Rose Bengal and Their Phototoxicity against Cancer Cells.

Photodynamic therapy (PDT) is an innovative technique for cancer treatment with minimal side effects, based on the use of a photosensitizer, oxygen, and light. Photosensitizers (PSs) have several limitations, that may limit their clinical use, like poor solubilization, self-aggregation, and lack of specific targeting, which can be addressed with the use of nanomaterials. Herein, a unique type of catansomes (CaSs) was prepared using a gemini imidazolium-based surfactant (1,3-bis[(3-octadecyl-1-imidazolio)methyl]benzene dibromide (GBIB) and a double chain surfactant, diaoctyl sodium sulfosuccinate or Aerosol OT (AOT). The formation of CaS GBIB/AOT was optimized in various ethanol/water (E/W) solvent ratios by employing a facile, quick, and most reliable solution-solution mixing method. The CaS was characterized by dynamic light scattering (DLS) and field emission gun scanning electron microscopy (FEG-SEM) techniques. The experimental results reveal that stable CaSs with a spherical shape were obtained at lower concentration (100 μM). Rose Bengal (RB), a PS of the xanthene family, was incorporated into these prepared CaSs, as proven by fluorescence spectroscopy, UV-visible absorption spectroscopy, and confocal laser scanning microscopy. Singlet oxygen (1O2) generation studies revealed the relevant role of the E/W solvent ratio as there was a 4-fold boost in the 1O2 production for GBIB/AOT in E/W = 50:50 and around 3-fold in E/W = 30:70. Also, the GBIB-rich 80:20 fraction was more efficient in increasing the 1O2 generation as compared to the AOT rich fraction (20:80). Further, their phototoxicity was tested in a water-rich solvent ratio (E/W = 30:70) against MCF-7 cells. Upon irradiation with a 532 nm laser (50 mW) for 5 min, RB@GBIB/AOT(20:80) fraction caused 50% decrease in the metabolic activity of MCF-7 cells, and RB@GBIB/AOT(80:20) fraction produced a maximum 85% decrease in cell viability. Furthermore, the enhancement in intracellular 1O2 generation by RB@GBIB/AOT, as compared to pure RB, was confirmed with singlet oxygen sensor green (SOSG). This new type of CaS based on gemini surfactants exhibiting a large amount of 1O2 generation, holds great interest for several applications, such as use in photomedicine in future.

Unraveling the effect of surfactant chain length on the binding interaction of curcumin with cationic and non‐ionic micelles

AbstractMajor drawbacks of using curcumin as a potential multifunctional drug are its very low water solubility and lack of bio‐availability. For this purpose we have used surfactants to increase the solubility of curcumin in aqueous medium and to assess its hydrophilic and hydrophobic interactions with micelles. In order to understand the molecular mechanism of the interaction of curcumin with surfactants, we have employed cationic and non‐ionic surfactants. We have used hexadecyl(cetyl)trimethylammonium bromide (CTAB), tetradecyltrimethylammonium (TTAB) and dodecyltrimethylammonium bromide (DTAB) as cationic surfactants of varying hydrocarbon tail dimension and octylphenol ethoxylate with 10 moles of ethyelene oxide (OPE‐10), octylphenol ethoxylate with 16 moles of ethyelene oxide (OPE‐16), octylphenol ethoxylate with 30 moles of ethyelene oxide (OPE‐30) as non‐ionic surfactants of varying poly(ethylene oxide) hydrophilic head dimension. From the increase in fluorescence intensity of curcumin in the presence of surfactants, we had estimated the apparent binding constant (Kb) of curcumin‐micelle complex formation. The evaluated Kb values between curcumin and CTAB, TTAB, and DTAB were 7.75 × 105, 3.44 × 105, and 0.78 × 105 L mol−1, respectively. In the case of non‐ionic surfactants, the estimated Kb values of curcumin with OPE‐10, OPE‐16, and OPE‐30 were 4.90 × 106, 3.82 × 106, and 0.58 × 106 L mol−1, respectively. Thus, it was found that Kb values were somehow greater in the case of non‐ionic surfactants than cationic surfactants. From the fluorescence quenching study it was revealed that the probable location of curcumin was the Stern layer and the palisade layer in the case of cationic and non‐ionic micelles, respectively. Our results might be useful to overcome challenges associated with the delivery of curcumin as a multifunctional drug molecule.

A guide to designing graphene-philic surfactants

HypothesisAs compared to common aliphatic surfactants, increasing the number of pendant or incorporated aromatic groups in a surfactant is expected to offer significant enhancement in the affinity for graphene surfaces. The basis for enhanced graphene-philicity of aromatic surfactants is that they can develop appreciable π – π interactions with graphene. Furthermore, charged (anionic) surfactants are expected to confer electrostatic stabilization on surfactant-graphene composites. Hence, it is expected that anionic aromatic surfactants combine these two properties for effective stabilization of graphene dispersions in water. ExperimentalThe properties of two custom made graphene-compatible surfactants carrying two and three aromatic moieties in the hydrophobic tails, namely DC3Ph2 (sodium 1,4-dioxo-1,4-bis(3-phenylpropoxy)butane-2-sulfonate) and TC3Ph3 (sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3-phenylpropoxy)carbonyl) pentane-2-sulfonate) were compared with other common ionic commercial surfactants. Air-water (a/w) surface tension measurements were used to assess the surfactant adsorption and interfacial packing in the absence and presence of graphene. The surfactant coverage index for graphene (Ф) was calculated using surfactant headgroup areas derived from a/w surface tension data, chain volumes, and molecular fragment volumes from literature. FindingsIncreasing the number of aromatic groups and tails per surfactant was shown to increase the ability of surfactants to pack and fill space, as expressed by Ф. Comparison between the values of Ф for surfactants of different chain structure and architecture showed that the affinity for graphene increased with Ф. Hence, there is an implicit link between surfactant-graphene compatibility and the identity, chemical composition and architecture of the surfactant chains.

Mixed Micellization, Thermodynamic and Adsorption Behavior of Tetracaine Hydrochloride in the Presence of Cationic Gemini/Conventional Surfactants.

In this approach, tensiometry and UV-visible techniques are used to determine the effect of cationic gemini and conventional surfactants on tetracaine hydrochloride (TCH), an anesthetic drug. We have estimated micellar, interfacial, and energetic constraints. To gain a deep understanding of their mixed association behavior, the outputs were examined using different theoretical models. The critical micelle concentration for single and mixed amphiphiles was estimated. The cmc values of mixed amphiphiles were found between the individual amphiphiles due to strong attractive interaction (synergism) between the components after mixing. The non-ideal behavior of mixtures was confirmed by the larger values of ideal cmc than the experimental cmc values. The negative values of interaction parameter (β) and values of activity coefficients less than unity indicate strong synergistic interaction between drug and surfactant. The stability of the mixed systems is demonstrated by the negative Gibbs free energy of micellization and excess free energy of micellization. In contrast to a single chain surfactant, a double chain surfactant (gemini) exhibits better interactions with the drug. Spectral measurements (UV-visible spectra) were used to monitor the binding of the drug with surfactant (conventional as well as gemini). Studying these mixed aggregates could help to optimize their compositions and find synergistic properties between TCH monomers and surfactants.

Increasing the Diameter of Vertically Aligned, Hexagonally Ordered Pores in Mesoporous Silica Thin Films.

The variation in pore size in mesoporous films produced by electrochemically assisted self-assembly (EASA) with the surfactant chain length is described. EASA produces a hexagonal array of pores perpendicular to the substrate surface by using an applied potential to organize cationic surfactants and the resultant current to drive condensation in a silica sol. Here, we show that a range of pore sizes between 2 and 5 nm in diameter is available with surfactants of the form [Me3NCnH2n+1]Br, with alkyl chain lengths between C14 and C24. The film quality, pore order, pore size, and pore accessibility are probed with a range of techniques.

Surfactant chemistry and polymer choice affect single-wall carbon nanotube extraction conditions in aqueous two-polymer phase extraction

Quantitative determination of the effects of surfactant chemistry and polymer chain length on the concentration conditions necessary to yield extraction of specific single-wall carbon nanotube (SWCNT) species in an aqueous two-polymer phase extraction (ATPE) separation are reported. In particular, the effects of polyethylene glycol (PEG) chain length, surfactant ratios, and systematic structural variations of alkyl surfactants and bile salts on the surfactant ratios necessary for extraction were investigated using a recently reported fluorescence-based method. Alkyl surfactant tail length was observed to strongly affect the amount of surfactant necessary to cause PEG-phase extraction of nanotube species in ATPE, while variation in the anionic sulfate/sulfonate head group chemistry has less impact on the concentration necessary for extraction. Substitution of different bile salts results in different surfactant packings on the SWCNTs, with substitution greatly affecting the alkyl surfactant concentrations required for (n,m) extraction. Finally, distinct alkyl-to-bile surfactant ratios were found to extract specific (n,m) SWCNTs across the whole effective window of absolute concentrations, supporting the hypothesized competitive adsorption mechanism model of SWCNT sorting. Altogether, these results provide valuable insights into the underlying mechanisms behind ATPE-based SWCNT separations, towards further development and optimization of the ATPE method for SWCNT chirality and handedness sorting.

Phase studies of ethyl ammonium nitrate (EAN)/sugar surfactant microemulsions: effect of chain length of alkanes and length of the hydrophobic chain of the non-ionic surfactant

Abstract Microemulsions were formulated with the ionic liquid ethylammonium nitrate (EAN) used instead of water as the polar phase, hydrocarbon solvents (n-alkanes) and sugar-based non-ionic surfactants, and their phase behaviour and microstructure were investigated. The sugar-based non-ionic surfactants used are non-toxic, biodegradable and environmentally friendly. Due to these properties, their use in microemulsion systems is a clear alternative to the conventionally used non-ionic surfactants from the class of alkyl polyoxyethylene ethers (C i E j ). The influence of n-alkanes with different chain lengths and of sugar-based nonionic surfactants with hydrophobic chains of different lengths on the microemulsion system was also investigated. The results obtained for the microemulsions with EAN described here are similar to those obtained for microemulsion systems formulated with water as the polar solvent. Liquid crystalline (LC) phases were observed in microemulsion systems with sugar-based nonionic surfactants having longer hydrocarbon chains, at lower temperatures and higher surfactant mass fraction.