Surfactant Chain Research Articles

Krafft Temperature, Critical Micelle Concentration, and Rheology of “Pseudo‐Gemini” Surfactant Comprising Fatty Acid Soap and Bola‐Type Quaternary Ammonium Salt

AbstractBola‐type quaternary ammonium salt can bridge with two fatty acid soaps through electrostatic attraction to form a pseudogemini surfactant, which enhances the solution viscosity. In this work, the effects of the building blocks (spacer and hydrophobic chain) of a pseudogemini surfactant on the Krafft temperature, critical micelle concentration, and rheological properties were investigated. The results revealed that the addition of bola‐type salt obviously decreased the Krafft temperature of sodium stearate (C18ONa), and a bola‐type salt bearing a large benzene ring (Bola2be) was more effective than the one bearing an ethyl group (Bola2et) or a hydroxyethyl group (Bola2hy). When bola‐type salt is mixed with fatty acid soap at a fixed molar ratio of 1:2, a pseudogemini surfactant forms in situ, and the viscosity of the solution is significantly enhanced by the formation of a worm‐like micelle (WLM) network. The stronger the hydrophobicity of the bola‐type salt or the tail of the fatty acid soap, the lower the critical overlapping and micelle concentrations, and the stronger is the ability to enhance viscosity. However, pseudogemini surfactants that use sodium stearate as a monomer show similar self‐assembly abilities to those using sodium oleate as a monomer. In addition, the WLM formed by pseudogemini surfactants composed of Bola2be and sodium stearate or sodium oleate were liable to branch at high concentrations.

Adsorption behaviour of surfactant-nanoparticles at the gas-liquid interface: Influence of the alkane chain length

Silica nanoparticles (NPs) have shown tremendous application potential as stabilising agents in foams. The adsorption of cationic surfactants on the surface of NPs through electrostatic interactions forms integrated surfactant-NP compounds and endows the NPs with surfactancy. The aim of this study was to investigate the influence of the alkane chain length of cationic surfactants on NP surfactancy and foam stability. The results demonstrate that the surface tension decreases and dilational elasticity modulus increases with surfactant chain length. Simultaneously, coalescence of bubbles is markedly suppressed and the stability of surfactant-NP foams is enhanced in static and dynamic tests. With a coarse-grained molecular dynamics simulation (CGMD), it was found that the surfactant-NP complexes evolve into an asymmetric Janus structure at the gas-liquid interface from their symmetric configuration in the aqueous phase. In addition, the resistance force during the pulling of a NP away from the interface increases with surfactant chain length. The simulation results imply that surfactant-NPs have a high surfactancy and the adsorption stability is improved with increasing surfactant chain length, which is in good agreement with the experimental results.

Phase diagram and surface adsorption behavior of benzyl dimethyl hexadecyl ammonium bromide in a binary surfactant-water system

Phase diagram provides valuable information to describe the phase and aggregation behavior of surfactants. In this study, surface adsorption behavior of benzyl dimethyl hexadecyl ammonium bromide (BDHAB) surfactant in water and their phase formations have been explored. The formation of lyotropic liquid crystalline (LLC) phases in the binary surfactant–water system was analyzed by polarized light microscopy (PLM). A comprehensive phase diagram was established presenting the existence of LLC phases as a function of surfactant concentration and temperature. The observed PLM images reveal that the BDHAB–H2O system exhibits isotropic (L1), hexagonal liquid crystalline (H1), cubic (V1), and lamellar (L∞) phases in a sequential pattern with the increase of surfactant concentration. The recorded LLC phases for bi-tail BDHAB–H2O system have also been compared with the phase diagram of single tail cetyl trimethyl ammonium bromide (CTAB)–H2O system. The present study evidence that the surfactant morphology (i.e., alkyl chain length and surfactant head-group area) has a significant influence on the formation of micellar aggregates. In addition, surface tension measurements were also performed to observe the surface adsorption behavior of BDHAB surfactant. This study will be beneficial in understanding the micelle formation and solubilization behavior of bi-tailed quaternary ammonium cationic surfactants to optimize its colloidal formulations.

Self‐Assembly of Polyethylene Glycol Ether Surfactants in Aqueous Solutions: The Effect of Linker between Alkyl and Ethoxylate

AbstractThe aqueous self‐assembly behavior of two homologous series of poly(ethylene oxide) (PEO)‐containing nonionic surfactants based on a C10‐Guerbet hydrophobe is reported. The two families of surfactants, alkyl ethoxylates and alkyl alkoxylates, are commercially available from BASF under the trade name Lutensol® XP‐series and XL‐series, respectively. The latter incorporate propylene oxide (PO) units in the surfactant chain. Dye solubilization was used to determine the critical micellization concentration (CMC) of each surfactant at 22 and 50 °C. The PO‐containing alkyl alkoxylates displayed lower CMC values, which were also more sensitive to temperature. The Gibbs free energy, enthalpy, and entropy of micellization were computed from the CMC data and used to identify the contribution of each surfactant moiety (alkyl chain, PO unit, and PEO block) in controlling the CMC. The micellization properties are compared with compositionally similar surfactants with linear alkyl chains, yielding information about the effects of the Guerbet alkyl chain on micellization. Isothermal titration calorimetry was also used to characterize the CMC and enthalpy of micellization which generally compare well with the dye solubilization results. Cloud point data reveal nonmonotonic relationships for the Lutensol® surfactants with respect to composition, unlike linear alkyl chain surfactants. Finally, dilute solution viscosity measurements performed on some Lutensol® surfactants show a change in the slope, suggesting a structural change that tends to be more pronounced for surfactants with longer PEO blocks. The data presented herein enhance the understanding of surfactant structure–property relationships required for industrial formulation.

Surfactant-mediated enzymatic superactivity in water/ionic liquid mixtures, evaluated on a model hydrolytic reaction catalyzed by α-chymotrypsin

In this work, the influence of the C12-, C14-, and C16-alkyl chain derivatives of 1-alkyl-3-methyl-imidazole tetrafluoroborate over the hydrolisis of p-nitrophenyl trimethylacetate catalyzed by α-chymotrypsin was studied in water and water - ionic liquids mixtures. The ionic liquid used is 1-butyl-3-methyl-imidazole tetrafluoroborate (BMIMBF4).1-alkyl-3-methylimidazole tetrafluoroborate derived surfactants can increase the catalytic efficiency of α-chymotrypsin on the hydrolysis of p-nitrophenyl trimethylacetate. This effect is negatively affected by the decrease on the surfactant's critical micelle concentration (CMC) and the partition of the substrate between the micelles and the external media observed above the critical miscellar concentration (CMC). In water/BMIMBF4 mixtures, the presence of the ionic liquid (IL), render the C14 and C16 surfactants insoluble, and overrides the effect elicited by the C12 alkyl chain surfactant on the activity of α-chymotrypsin. The loss of the surfactants influence on the enzymatic activity due to the presence of BMIMBF4 seems to be a complex process, controlled by a decreased affinity between α-chymotrypsin and the surfactant molecules and, to a larger extent, the appearance of an “acquired resistance” of the enzyme to the influence of the surfactants, related to a more compact and resilient conformation of the protein in the presence of BMIMBF4. The influence of BMIMBF4 is not only limited to the surfactant/enzyme interaction, but also it does modifies the partition of the substrate between the aqueous media and the micellar environment.

A co-delivery platform based on plasmid DNA peptide-surfactant complexes: formation, characterization and release behavior.

The development of delivery systems based on cell penetrating peptides represents an incredible asset and may deeply contribute for the evolution of therapies efficacy. In this context, we explore the plasmid DNA (pDNA) condensation ability of TAT peptide to produce a suitable intracellular delivery platform. The nanoparticles were formed at various ratios of nitrogen to phosphate groups (N/P) and the variation of polyplexes properties with this parameter was studied. Beyond the large size exhibited by these carriers, their low pDNA immobilization profile instigates the need for an additional compacting agent. To maximize the performance of this peptide delivery system, a series of alkyl trimethyl ammonium bromide surfactants (CnTAB) were employed to further condense pDNA. In general, not only this strategy promotes the formation of lower sized vectors, but also greatly enhances particle characteristics such as surface charge and pDNA encapsulation. The magnitude of this effect is intimately dependent on surfactant chain length. Furthermore, the known cytotoxicity of cationic surfactants has been dramatically reduced by their incorporation into TAT/pDNA complexes. The release kinetics can be tailored and optimized to promote the controlled/sustained release of pDNA. Following this, the surfactant alkyl chain length and the N/P ratio are important controlling parameters. In addition, doxorubicin and paclitaxel can be efficiently loaded and encapsulated into peptide/pDNA/surfactant carriers. The presented platform reveals a great potential for therapeutic payloads loading and controlled release open advanced and new approaches in the design/formulation of innovative biomedical systems towards clinical translation.

A New Class of Low Surface Energy Anionic Surfactant for Enhanced Oil Recovery

A highly branched green low surface energy surfactant (LSES), stable in harsh conditions, was synthesized for enhanced oil recovery (EOR). Oil recovery factors were determined using a glass micromodel and indicated a 72% increase in oil recovery in both low and high brine solutions, a remarkable result for only a single chain surfactant flooding. The surface-interface analysis of brine and brine/surfactant solutions was carried out, while small-angle neutron scattering measurements were used to determine the changes in the surfactant structure in different brine solutions, and ζ potential experiments revealed the effect of monovalent and divalent cations in each solution. Adsorption analysis on crushed glasses was evaluated to see the maximum amount of surfactant adsorption in the system, and finally, oil recovery factors were discussed according to the interfacial tension and contact angle measurements. Based on our inclusive study we conclude that the cost-effective and environmentally friendly LSES presents a class of potentially important material for use in various EOR scenarios, such as low salinity, smart water, alkaline–surfactant–polymer, and nanoparticle–surfactant flooding.

Synthesis and characterization of a novel surfactant used for aqueous film-forming foam extinguishing agent

Fluorocarbon surfactants are a key ingredient of aqueous film-forming foam (AFFF) extinguishing agent. As is well known, the most widely used fluorocarbon surfactants are perfluorooctane sulfonates (PFOS) and theirs derivatives. However, PFOS has been restricted due to its drawbacks such as toxicity, bio-accumulation and resistance to biodegradation, etc. Fortunately, the toxicity and bio-accumulation can be neglected if the fluorocarbon chain contained in the surfactants is less than or equal to 4. Therefore, synthesis of novel short fluorocarbon chain (≤ C4) surfactants has become a very important way to solve this problem. A novel fluorocarbon surfactant based on perfluorobutyl had been synthesized and its chemical structure had been confirmed by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance (NMR) and 19F NMR measurements in this work. Since the fluorocarbon surfactant mixed with appropriate hydrocarbon surfactant can reduce its dosage and cutting production costs, the surface tension and the critical micelle concentration (CMC) of the synthesized fluorocarbon surfactant and its equimolar mixtures with CH3(CH2)5NaO3S had been studied. The results show that CMC and the surface tension at CMC (γCMC) of the pure surfactant were 21.68 mmol/L and 17.08 mN/m, while the minimum surface tension and CMC could reach to 16.58 mN/m and 7.72 mmol/L for the mixed system, respectively. In addition, the foamability, spreadability and extinguishing performance of the equimolar mixed system has also been investigated. The foam expansion and the 25% drainage time are 9.8 and 313 s, respectively, and the extinguishing times are less than 65 s while the burnback times are more than 14.50 min for all the hydrocarbon oils studied in this work, indicating a great application prospect in AFFF.

Reaction between Zinc and Hydrochloric Acid in Solutions Containing Alkyltrimethylammonium Bromide CnTAB (n = 8, 10, and 12) Cationic Surfactants: Influence of Surfactant Chain Length

AbstractThe influence of CnTAB cationic surfactant chain length (n = 8, 10, and 12) on the reaction rate of zinc powder and 0.1 M HCl hydrochloric acid in aqueous solutions was determined at room temperature. Solutions of single surfactants consisting of dodecyl, decyl, and octyl‐trimethyl‐ammonium bromide surfactants CnTAB were prepared at room temperature. From the surface tension and conductivity measurements, the critical micelle concentration (CMC) values of the three surfactants were obtained in the presence and absence of the acid. No significant change was observed for CMC values in pure water and in 0.01 M HCl. Adsorption of CnTAB surfactants onto 1% wt./vol zinc (in powder form), using surface tension measurements, was then investigated. The adsorption tendency of CnTAB surfactants onto zinc powder followed the order: C8TAB > C10TAB > C12TAB. The role of surfactants in the reaction rate between zinc powder and 0.1 M M HCl was then investigated using conductivity measurements. A significant difference in the reaction rate was found depending on the surfactant chain length. Reaction times of 3830, 4963, 14,172, and 20,053 s were found for the zinc reaction with (0.1 M HCl), (0.1 M HCl + 40 mM C8TAB), (0.1 M HCl + 40 mM C10TAB), and (0.1 M HCl + 40 mM C12TAB), respectively, suggesting a significant dependency of the reaction rate on the CnTAB chain length. Finally, some corrosion parameters such as the corrosion rate, corrosion inhibition efficiency, and their dependency on CnTAB chain length were presented and discussed.

The Effect of Surfactant Chain Length and Type on the Photocatalytic Activity of Mesoporous TiO2 Nanoparticles Obtained via Modified Sol-Gel Process

Mesoporous amorphous and nanocrystalline titanium dioxide were prepared by simple and environmental friendly modified Sol-Gel method using cationic (C14TAB, C16TAB, C18TAB) and nonionic (Plantacare UP K55) surfactant as pore forming agent. The obtained particles were characterized by BET, TEM, FT-IR and XRD techniques. The effect of cationic surfactant chain length and type of template on the photocatalytic activity of as prepared TiO2 nanoparticles were investigated by the degradation of rhodamine B in water solution under UV irradiation. The results indicated that this process was well described by pseudo-first order kinetic model. All the prepared titanium dioxide particles with cationic and nonionic surfactant exhibited higher performance for rhodamine B photo-degradation. The sample with large pore size and small particle size which obtained by using C18TAB surfactant showed high photocatalytic activity compared with the others samples and commercial P25. The mechanism of photocatalytic degradation of rhodamine B was proposed based on the degradation products determined by GC/MS and LC/MS. The performance of the recycled TiO2 as photocatalyst was investigated.

Competitive Adsorption of a Multifunctional Amine and Phenol Surfactant with Ethanol on Hematite from Nonaqueous Solution.

Surfactants, which contain phenol and amine groups, are commonly used in industries to protect metallic surfaces, and their efficiency depends strongly on factors such as pressure and temperature, solvent properties, and the presence of other surfactants in the system. In this work, we present a molecular simulation study of the competitive adsorption between a multifunctional phenol and amine surfactant model and ethanol at the oil/solid interface formed between iso-octane and a model hematite (α-Fe2O3) slab. We show that the surfactant strongly adsorbs at the iso-octane/hematite interface in the absence of ethanol at moderate temperatures. As the concentration of ethanol is increased, the ethanol molecules compete effectively for the adsorption sites on the iron oxide surface. This competition drives the surfactant molecules to remain in the bulk solution, while ethanol forms ordered and strongly coordinated layers at the oil/solid interface, despite the well-known complete miscibility of ethanol in iso-octane in bulk under standard conditions. Potential of mean force calculations show that the free energy of adsorption of the surfactant is approximately two times larger than that for a single ethanol molecule, but the simulations also reveal that a single surfactant chain needs to displace up to five ethanol molecules to adsorb onto the surface. The end result is more favorable ethanol adsorption which agrees with the experimental analysis of similar oil/iron oxide systems also reported in this work.

Study on Stabilizing Emulsion by Mixing Nano-silica and Cationic Surfactants with Different Chain Length

Considering the interaction between the electronegative nano-silica (NS) and cationic surfactant, this paper aims at studying the effect of NS modified by cationic surfactants with different chain length on emulsion behavior. These effects on emulsion behavior were investigated at two aspects: emulsion stability and rheological characteristics. Experimental results indicated that flocculation of nano-silica becomes easier with longer alkane chains. While the chain length increases within the studied concentration range, the threshold concentration of surfactants at which the intermediate phase emulsion appears decreases. For NS and DETAB together in dispersion, no phase inversion appeared. The NS surface hydrophilic-lipophilic balance was changed due to the enwind of the alkane chain. Longer alkane chain adsorbs on the NS surface and reaches saturation at the same surfactant concentrations more easily due to the different enwind degrees of alkane chains. It is suggested that the different surfactant chains had different enwind degrees on the liquid-liquid interface. Rheological experiments show that the emulsion has shear dilution and elasticity.

Rheological properties of an ultra-high salt hydrophobic associated polymer as a fracturing fluid system.

Herein, a novel ultra-high salt hydrophobic associated polymer, UUCPAM, was prepared using acrylamide, acrylic acid, 2-acrylamide-2-methyl propane sulfonic acid and the hydrophobic monomer UUC. Polymerization exothermic test results indicated that the increase in the hydrophobic monomer content led to an increase in the exothermic time, which is considerably conducive to the formation of hydrophobic structures. The scanning electron microscopy and transmission electron microscopy studies showed that the polymer had complex network structures and that this phenomenon was considerably obvious in NaCl solution. The fluorescence probe experiment verified that the critical association concentration of this polymer decreased with an increase in the hydrophobic monomer. Rheology studies indicated that the polymer had good temperature and shear resistance in NaCl solution. Moreover, the apparent viscosity of the polymer remained above 80 mPa s when 0.3 wt% UUCPAM was added at 170 s−1 in 20 000 mg L−1 NaCl solution at 90 °C. The storage modulus that indicated strong elasticity increased with an increase in the polymer concentration. Meanwhile, the number of hydrophobic micro-zones increased, thus forming dense network structures. Therefore, the polymer was found to have excellent salt resistance and extensive application prospects.

Molecular packing of surface active ionic liquids in a deep eutectic solvent: a small angle X-ray scattering (SAXS) study.

During the past decade, deep eutectic solvents (DESs) have shown promising application in the self-assembly of surfactants. Various aggregates such as micelles, vesicles, lyotropic liquid crystals, microemulsions and gels have been reported. In this research, the phase behaviours of imidazolium surface active ionic liquids (SAILs) CnmimBr (n = 12, 14, 16) were investigated in ChG. With the help of small angle X-ray scattering (SAXS), the types and structure parameters of aggregates were determined. The molecular packing of SAILs was influenced by the solvophobic chain length, surfactant concentration, temperature and solvent, accounting for their different aggregation behaviours. This study would give a good description of the molecular packing of surfactants in DESs.

CnTAB/polystyrene sulfonate mixtures at air-water interfaces: effects of alkyl chain length on surface activity and charging state.

Binding and phase behavior of oppositely charged polyelectrolytes and surfactants with different chain lengths were studied in aqueous bulk solutions and at air-water interfaces. In particular, we have investigated the polyanion poly(sodium 4-styrenesulfonate) (NaPSS) and the cationic surfactants dodecyltrimethylammonium bromide (C12TAB), tetradecyltrimethylammonium bromide (C14TAB) and cetyltrimethylammonium bromide (C16TAB). In order to reveal the surfactant/polyelectrolyte binding, aggregation and phase separation of the mixtures, we have varied the NaPSS concentration systematically and have kept the surfactant concentration fixed at 1/6 of the respective critical micelle concentration. Information on the behavior in the bulk solution was gained by electrophoretic mobility and turbidity measurements, while the surface properties were studied using surface tension measurements and vibrational sum-frequency generation (SFG). This has enabled us to relate bulk to interfacial properties with respect to the charging state and the surfactants' binding efficiency. We found that the latter two are strongly dependent on the alkyl chain length of the surfactant and that binding is much more efficient as the alkyl chain length of the surfactant increases. This also results in a different phase behavior as shown by turbidity measurements of the bulk solutions. Charge neutral aggregates that are forming in the bulk adsorb onto the air-water interface - an effect that is likely caused by the increased hydrophobicity of CnTAB/PSS complexes. This conclusion is corroborated by SFG spectroscopy, where we observe a decrease in the intensity of O-H stretching bands, which is indicative of a decrease in surface charging and the formation of interfaces with negligible net charge. Particularly at mixing ratios that are in the equilibrium two-phase region, we observe weak O-H intensities and thus surface charging.

Self-assembly of mixed dodecylamine–dodecanol molecules at the air/water interface based on large-scale molecular dynamics

Dodecylamine (DDA)–alcohol mixtures have motivated great interest recently due to their superior performance in industrial processes compared with pure DDA. Self-assembly of surfactants at the air/water interface plays an important role in their surface properties. However, the self-assembly of mixed DDA–alcohol at an atomic level is still unknown. In this study, large-scale atomistic dynamic simulations of DDA–dodecanol (DOD) mixtures with different ratios were performed to clarify their molecular arrangement and explain the synergistic effect. The structural properties, such as molecular aggregation, orientation, angle distributions, and H bond distributions, of DDA–DOD mixtures were characterized in detail. Simulation results show considerable differences in the behavior of mixed DDA–DOD molecules with different ratios. The self-assembly of pure DDA molecules is not significant due to the strong electrostatic repulsion between head groups. The surface activity of pure DOD molecules is not strong due to their poor water solubility based on their fewer amounts of H-bonds with water. For mixed DDA–DOD, the addition of DOD does not directly affect the arrangement of DDA molecules; rather, DOD molecules insert between DDA molecules and form stable clusters at the air/water interface due to the van der Waals interactions between surfactant chains. Two main interaction patterns exist between DDA and DOD, including van der Waals interactions between the surfactant chains and H bonds between their head groups. DOD and DDA play an important role in forming the cluster and solvent action, respectively. The ratio of these two surfactants can affect the two above properties. This study provides a good strategy to investigate the self-assembly cluster of mixed surfactants and supports the experimental theory at the atomic level.

Introduction of Positive Charges into Zwitterionic Phospholipid Monolayers Disrupts Water Structure Whereas Negative Charges Enhances It.

The interfacial water structure and phosphate group hydration of 1,2-dioleoyl- sn-glycero-3-phosphatidylcholine monolayers were investigated at air/water interfaces. Both vibrational sum frequency spectroscopy (VSFS) and Langmuir monolayer compression measurements were made. The PC lipids oriented water molecules predominantly through their phosphate-choline (P-N) dipoles and carbonyl moieties. Upon the introduction of low concentrations of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP), a positively charged double chain surfactant, the TAP headgroups were attracted to the phosphate moieties on adjacent PC lipids. This attraction caused the monolayers to contract, expelling water molecules that were hydrogen bonded to the phosphate groups. Moreover, amplitude of the OH stretch signal decreased. At higher DOTAP concentrations, the positive charge on the monolayer caused an increase in the area per headgroup and water molecules in the near-surface bulk region became increasingly aligned. Under these latter conditions, the OH stretch amplitude was linearly proportional to the surface potential. By contrast, introducing 1,2-dioleoyl- sn-glycero-3-phosphatidylglycerol, a negatively charged lipid, did not change the area per lipid or the phosphate-water hydrogen bonding network. As the interfacial potential grew more negative, the OH stretch amplitude increased continuously. Significantly, changes in the interfacial water spectrum were independent of the chemistry employed to create the positive or negative interfacial potential. For example, Ca2+ and tetracaine (both positively charged) disrupted the water structure similarly to low DOTAP concentrations, whereas SCN- and ibuprofen (both negatively charged) enhanced the water structure. These results suggest a direct correlation amongst the interfacial water structure, area per lipid, and surface charge density.

Surfactant assisted CaO-based sorbent synthesis and their application to high-temperature CO2 capture

The concern of carbon dioxide (CO2) emissions, a main contribution of greenhouse gases, has been emerged as an important issue for environmental impact. Adsorption of CO2 by porous solid materials is proven to be one of efficient techniques for CO2 capture technologies. In the present work, attempted has been made to improve property of porous solid materials, CaO-based sorbent, applied for high-temperature CO2 capture. CaCO3 and CaO-based alumina was synthesized using precipitation technique with the addition of sulfonic single chain (SDS) and gemini (12-carbon hydrophobic chains and 3-carbon alkyl spacer, 12-3-12) surfactants for controlling/modifying physical properties. Our studies showed that the addition of anionic surfactants affected phase formation and polymorph of CaCO3, where stronger effect was observed with gemini surfactant. The synthetic CaCO3 was derived to form CaO and applied for capturing CO2 at 600 °C, 15% v/v CO2 (N2 balanced). The results showed that CaO synthesized with adding gemini surfactant offered higher CO2 sorption capacity than single chain surfactant. By incorporating calcium with alumina using co-precipitation technique, the addition of gemini surfactant showed a good impact on CO2 capture performance as an increase in CO2 sorption capacity was observed. However, sintering effect was still not yet be resolved with the addition of gemini surfactant as CO2 sorption capacity decreased upon multiple cycles of CO2 capture.

Cationic gemini surfactant templated magnetic cubic mesoporous silica and its application in the magnetic dispersive solid phase extraction of endocrine-disrupting compounds from the migrants of food contact materials

A cationic gemini surfactant templated magnetic cubic mesoporous silica Fe3O4@14-3-14-MCM-48 nanocomposite was successfully synthesized and utilized in the magnetic dispersive solid phase extraction (MDSPE) of nine endocrine-disrupting compounds (EDCs) from the migrants of food contact materials by high performance liquid chromatography with diode array detection (HPLC–DAD). Fe3O4@14-3-14-MCM-48 can interact with EDCs through electrostatic interactions, hydrophobic effect, and hydrogen bonding effect. It showed excellent adsorption performance for EDCs with short alkyl chain phenols, which showed higher hydrophilicity and less retained by normal mesoporous silica with single chain surfactant as template. The parameters affecting MDSPE efficiency were optimized, and the optimum extraction conditions were adsorbent amount, 20 mg; elution solvent, methanol/acetonitrile mixture at 50/50 (v/v); NaCl concentration, 30 g/L; sample pH 5.0. Under the optimized condition, the limits of detection and limits of quantification were in the range of 1.0–2.5 and 2.9–7.5 ng/mL, respectively. Good linearity was observed in the range of 10–200.0 ng/mL with correlation coefficients of >0.997 and the recoveries were in the range of 92.6–102.3%. The developed method was successfully applied to the detection of phenolic EDCs migrants from food contact materials.

Sono-RAFT Polymerization-Induced Self-Assembly in Aqueous Dispersion: Synthesis of LCST-type Thermosensitive Nanogels

The first sonochemically induced reversible addition–fragmentation chain transfer by the polymerization-induced self-assembly process (Sono-RAFT-PISA) has been investigated. High-frequency ultrasound (490 kHz, 40 W) was applied for the controlled polymerization of N-isopropylacrylamide (NIPAM) in aqueous dispersion via the Sono-RAFT-PISA technique using poly(poly(ethylene glycol) methyl ether acrylate) (PPEGA) as both macromolecular chain transfer agent and surfactant (macro-transurf). The synthesis of PPEGA-b-PNIPAM copolymers in aqueous media at 20 °C (DPn,NIPAM = 204) was found to reach total NIPAM conversion in a short time (60 min.) with narrow molecular weight distribution (Đ < 1.26). Furthermore, PNIPAM-based spherical nanogels (Dh ≤ 69 nm, pdi ≤ 0.26) were successfully synthesized by Sono-RAFT-PISA (aqueous dispersion, 45 °C), qualifying as a highly “green” method due to the complete monomer conversion, absence of organic initiator, of residues, and to the unique use of water as initiator and solv...