New ester based gemini surfactants: the effect of different cationic headgroups on micellization properties and viscosity of aqueous micellar solution

Ordered Mesoporous Silica Prepared with Biodegradable Gemini Surfactants as Templates for Environmental Applications

Mesoporous silica sieves have been prepared through sol-gel synthesis using diester gemini surfactants as pore templates, aiming to obtain new materials with potential use for water remediation. A series of mesoporous spherical silica particles of submicron size have been prepared in an alkali-catalyzed reaction, using a tetraethyl orthosilicate precursor and bis-quaternary ammonium gemini surfactants with diester spacers of varied lengths as pore-forming agents. The effect of the spacer length on the particle morphology was studied using nitrogen porosimetry, small-angle X-ray scattering (SAXS), ultra-small-angle neutron scattering, scanning, and transmission electron microscopy (SEM, TEM). The results revealed that for all spacer lengths, a long-range hexagonal pore ordering developed in the materials. The silica particles were nearly spherical, with sizes below 1 micrometer, and a weak dependence of the mean particle size on the spacer length could be observed. The template removal procedure had a strong influence on the porosity: calcination caused a moderate shrinkage of the pores while retaining the hexagonal structure, whereas treatment with acidified ethanol resulted in only partial removal of the surfactants; however, the hexagonal structure was severely destroyed. The applicability of the obtained calcined materials as adsorbents for heavy metal ions from water was studied with the example of Pb(II). A high sorption capacity of 110 mg/g was obtained in batch experiments, at pH 5 and 4 h contact time.

A water-responsive calix[4]resorcinarene system: self-assembly and fluorescence modulation

This study explores how water content modulates the self-assembly and fluorescence behavior of two novel calix[4]resorcinarene macrocycles. These macrocycles transition from large, flattened structures in pure THF to large giant vesicles (500-5000 nm) coexisting with small micelles (3.4-3.5 nm) as the water percentage in THF/water mixtures increases up to 53%. At higher water percentages, the assemblies become smaller, forming unimodal micelles with diameters of approximately 140-160 nm. Fluorescence quenching is observed upon water addition, attributed to nonradiative deactivation. These findings highlight water as a key regulator of the assembly and fluorescence of these calix[4]resorcinarene macrocycles, paving the way for further development of water-responsive calixarene systems.

The effect of water in THF/water mixtures on CMC, aggregation sizes, and fluorescence quenching of a new calix[4]resorcinarene macrocycle

This study explores how water content modulates the self-assembly and fluorescence behavior of a novel calixarene, C1. C1 forms large, flattened structures in pure THF, but water addition triggers a transition to smaller, unimodal clusters. A critical micellar concentration (CMC) is identified, decreasing with increasing water content. Fluorescence quenching is observed upon water addition, attributed to nonradiative deactivation. These findings highlight water as a key regulator of C1's assembly and fluorescence, paving the way for further development of water-responsive calixarene systems.

Synthesis and properties of ester functionalized cationic Gemini surfactants with amide groups

In this paper, a novel series of ester-functionalized cationic Gemini surfactants with amide groups (abbreviated as C m -(BAE)-C m (m = 12, 14, 16)) were synthesized and their surface tension as well as the thermodynamic surface parameters were determined with conductivity and fluorescence measurements, respectively. The structures of these Gemini surfactants were characterized by FT-IR, 1H NMR, and MS. The Krafft points of the three surfactants are below 0 °C, indicating better water solubility. The critical micelle concentration (CMC) of these surfactants decreases with the increase in the length of hydrophobic chain. The micellization process of these surfactants was found to be entropy-driven. The polar functional ester groups in the spacer form hydrogen bonds with water molecules, which increases the solubility of these Gemini surfactants in aqueous systems, facilitates the aggregation of their monomers and improves the stability of their micelles.

A slip-spring framework to study relaxation dynamics of entangled wormlike micelles with kinetic Monte Carlo algorithm

HYPOTHESIS

Wormlike micelles (WLMs) formed due to the self-assembly of amphiphiles in aqueous solution have similar viscoelastic properties as polymers. Owing to this similarity, in this work, it is postulated that kinetic Monte Carlo (kMC) sampling of slip-springs dynamics, which is able to model the rheology of polymers, can also be extended to capture the relaxation dynamics of WLMs.

THEORY

The proposed modeling framework considers the following relaxation mechanisms: reptation, union-scission, and constraint release. Specifically, each of these relaxation mechanisms is simulated as separate kMC events that capture the relaxation dynamics while considering the living nature of WLMs within the slip-spring framework. As a case study, the model is implemented to a system of sodium oleate and sodium chloride to predict the linear rheology and the characteristic relaxation times associated with the individual relaxation mechanisms at different pH and salt concentrations.

FINDINGS

Linear rheology predictions were found to be in good agreement with experimental data. Furthermore, the calculated relaxation times highlighted that reptation contributed to a continuous increase in viscosity while union-scission contributed to the decrease in viscosity of WLM solutions at a higher salinity and pH. This manifests the proposed model's capability to provide insights into the key processes governing WLM's rheology.

Preparation of a Gemini Surfactant from Mixed Fatty Acid and its Use in Cosmetics

Among the surfactants, dimeric surfactants represent a niche group with multifunctional properties. In this work a modified gemini surfactant was synthesized using symmetrical fatty acids. Due to the spacers used to combine the two symmetrical monomers, the synthesized gemini surfactant is cationic. The structure of the compound was confirmed with 1H-NMR. The most advantageous property of the gemini surfactant is that it has a lower surface tension, i. e. less than 35 mNm–1 at 25°C, compared to monomeric surfactants. The surface tension was determined with a Kyowa tensiometer. The CMC (critical micelle formation concentration) was calculated according to the pyrene method and detected by UV spectroscopy at 25°C. The very low CMC is another market advantage of the gemini surfactant. Hydrophobicity and hydrophilicity of the synthesized compound were checked by the emulsification method. The ability of the synthesized gemini surfactant to wet and foam and the emulsification index at different pH values were tested. Based on the results, the gemini surfactant was used in formulations for hair and skin care. Conditioners and creams were prepared with the synthesized compound and the properties were analyzed at different concentrations of the gemini surfactant in the respective formulation.

Enhancement of A Cationic Surfactant by Capping Nanoparticles: Synthesis, Characterization and Multiple Applications

There is scarce information on cationic surfactants’ biocidal and corrosion inhbibition effects on Slime-Forming Bacteria (SFB) isolated from oil field formation water. Therefore, this work focused on the the synthesis of a cationic surfactant (CS) to increase its features by capping different metal nanoparticles (zinc, ZnNPs-C-CS; manganese, MnNPs-C-CS and tin, SnNPs-C-CS) and used them as biocides and corrosion inhibitors. The cationic surfactant was synthesized and characterized by Fourier-Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Afterwards, different nanoparticles were synthesized, characterized, and exploited to cap by the CS. The CS and the different nanoparticles capped by the CS were tested for their antimicrobial susceptibility against standard bacterial and yeast strains. The synthesized compounds were further evaluated as anti-biofilms agents against positively-developed bacterial biofilms. Moreover, the CS and the ZnNPs-C-CS, MnNPs-C-CS, and SnNPs-C-CS were assessed as potential biocides against SFB, particularly Pseudomonas sp. (isolated from contaminated formation water), and as corrosion inhibitors against cultivated salinity. The results revealed the great effect of the different CS-capped NPs as broad-spectrum antimicrobial and anti-biofilm agents at lower Minimum Inhibitory Concentrations (MICs), Minimum Bactericidal Concentrations (MBCs), Minimum Fungicidal Concentrations (MFCs) and Minimum Biofilm Inhibitory Concentrations (MBICs), and the activities were reported in order of SnNPs-C-CS > MnNPs-C-CS > ZnNPs-C-CS > CS. Furthermore, the ZnNPs-C-CS, MnNPs-C-CS, and SnNPs-C-CS demonstrated biocidal and corrosion inhibition effects against Pseudomonas sp. at a salinity of 3.5% NaCl, with metal corrosion inhibition efficiencies of 88.6, 94.0 and 96.9%, in comparison to a CS efficiency of 85.7%. In conclusion, the present work provides a newly synthesized cationic surfactant and has enhanced its antimicrobial and its metal corrosion inhibition effects by capping different nanoparticles, and it has been successfully applied against slime-forming bacteria at a salinity of 3.5% NaCl.

Spreading of benquitrione droplets on superhydrophobic leaves through pillar[5]arene-based host–guest chemistry

Spreading of agricultural sprays on plant surfaces is a significant task as it helps decrease pesticide usage and thereby reduces the risk of environmental pollution.

Monolayer formed by l-Asp-based gemini surfactants self-assembled in 1D nanostructures

Herein, studies on the surface activities of newly synthesized l-Asp-based gemini surfactants, both nonionic and anionic, are presented. Conductometry, tensiometry, and the Langmuir-Blodgett (LB) film technique were applied for this purpose. π-A isotherms were obtained with a Langmuir trough and Wilhelmy balance. The structures of the monolayers assembled at the air/water interface and those deposited as LB films were studied via Brewster angle microscopy (BAM) and atomic force microscopy (AFM). The 2D films formed by the anion-active compounds show a well-known pattern of a monolayer film, whereas the nonionogenic amphiphiles have been found to be 1D structures with nano-widths and micro-lengths that align with each other during the process of compression; this is the first study where the organization of 1D fibrils in 2D films during compression is reported. The scanning electron microscopy (SEM) study reveals that 1D nanostructure formation is an intrinsic tendency of these molecules as not only nonionogenic surfactants, but also the anion active representatives have been constructed in the solid state by fibrillary structures.

Biophysical investigation of the interaction between cationic biodegradable Cm-E2O-Cm gemini surfactants and porcine serum albumin (PSA)

The interaction of porcine serum albumin (PSA) with biodegradable, less cytotoxic C_m-E2O-C_m gemini surfactants was monitored using state-of-the-art techniques. The temperature variation fluorescence experiments were used to derive the thermodynamic parameters of non-covalent interaction in PSA-C_m-E2O-C_m gemini systems, which indicate an exothermic and a hydrogen bonding/Van der Waals force predominated binding process. Synchronous fluorescence spectra indicate that tryptophan fluorescence gets more quenched than the tyrosine fluorescence. The pyrene micropolarity assay signifies that pyrene is subjected to mild micropolarity changes. UV absorption spectra verify the ground state complexation between PSA and C_m-E2O-C_m geminis. Far-UV CD spectra reveal negligible changes in secondary structure with respect to PSA in its native state. These results indicate that the cationic C_m-E2O-C_m geminis, at lower concentrations, substantially bind to PSA but do not disrupt its secondary structure. These observations are favorable for the potential utilization of the concerned geminis in the field of drug delivery, especially in self-emulsifying drug delivery systems.

Aggregation behaviour of biocompatible choline carboxylate ionic liquids and their interactions with biomolecules through experimental and theoretical investigations

The self-assembly of long-chain choline carboxylates accompanied by their interaction with BSA protein were investigated with focus on environmental sustainability.

Advances in the synthesis, molecular architectures and potential applications of gemini surfactants

Gemini surfactants have been the subject of intensive scrutiny by virtue of their unique combination of physical and chemical properties and being used in ordinary household objects to multifarious industrial processes. In this review, we summarize the recent developments of gemini surfactants, highlighting the classification of gemini surfactants based on the variation in headgroup polarity, flexibility/rigidity of spacer, hydrophobic alkyl chain and counterion along with potential applications of gemini surfactants, depicting the truly remarkable journey of gemini surfactants that has just come of age. We have focused on those objectives which will act as suitable candidates to take the field forward. The preceding information will permit us to estimate the effect of structural variation on the aggregation behavior of gemini surfactants for nanoscience and biological applications like antimicrobial, anti-fungal agent, better gene and drug delivery agent with low cytotoxicity and biodegradability, which makes them more advantageous for a number of technological processes and hence reduces the impact of these gemini surfactants on the environment.

Physicochemical Evaluation of Micellar Solution and Lyotropic Phases Formed by Self-Assembled Aggregates of Morpholinium Geminis

The micellar solution and the lyotropic liquid crystalline phases formed by gemini surfactants containing morpholinium headgroups are investigated for their self-aggregation and physicochemical properties in water. These gemini surfactants demonstrated good surface activity because they are able to undergo micellization at lower concentration and form nanosized micellar aggregates in dilute aqueous solution. The binary mixture of the morpholinium gemini surfactant-water system is investigated over a wide range of concentrations. The micellar solution of the morpholinium gemini surfactants demonstrated Newtonian fluidlike behavior between 10 and 50 wt % as the observed viscosities were independent of the applied shear rate. At higher concentration, morpholinium geminis formed self-assembled lyotropic phases in water. These liquid crystalline phases were characterized by small-angle X-ray scattering and polarized optical microscopy techniques.

Positive charge pesticide nanoemulsions prepared by the phase inversion composition method with ionic liquids

We prepared highly stable positive charge nanoemulsions with ILs that possessed fine wetting and adhesive property on wheat leaf surfaces.

Effect of counterions on the micellization and monolayer behaviour of cationic gemini surfactants

The effect of various inorganic and organic counterions on the aggregation behavior of gemini surfactants was examined to investigate the dominant influence of the anions on their micellization and aggregation behavior.

Sustainable oleic and stearic acid based biodegradable surfactants

Renewable ester functionalized fatty acid based imidazolium surfactant.

Micellization of long-chain ionic liquids in deep eutectic solvents

The aggregation behavior of the ionic liquid (IL) 1-alkyl-3-methylimidazolium chloride with different alkyl chain lengths in a deep eutectic solvent (DES, composed of choline chloride and glycerol in a 1 : 2 mole ratio) was studied for the first time. The critical micellar concentration, micellar size and intermolecular interactions in IL/DES solutions were investigated by different techniques including the fluorescence probe technique, small angle X-ray scattering and Fourier transform infrared spectroscopy. The solvophobic effect dominates the micellization of CnmimCl in DES and the intermolecular hydrogen-bond interaction plays a positive role to promote micelle formation. The micellar solutions were utilized for the synthesis of the water-unstable metal-organic framework Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate) at room temperature. X-Ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption isotherms confirm the formation of crystalline Cu3(BTC)2 nanocrystals with mesoporous structures. The morphologies and porosity properties of Cu3(BTC)2 nanocrystals can be modulated by varying the concentration of CnmimCl.