Quaternary Ammonium Surfactants Research Articles

Chain Friction and Lubrication Balanced Ultra-Tough Polyacrylates With Wide-Span Switchable Stiffness for Strain-Programmable Deformation.

Natural mollusks perform complex mechanical actions through reversible large-strain deformation and stiffness switching, which are challenging to achieve simultaneously in synthetic materials. Herein, it is shown that a set of polyacrylates designed according to a chain friction and lubrication balanced strategy showsultra-stretchability (λ up to 324), high resilience (near 100% recovery at strain ≥ 100), and wide-span stiffness switching (up to 2073 times). The typical emulsion polymerization method and casting technique are adopted to fabricate the polyacrylate films. Quaternary ammonium surfactants are used as the emulsifier and reserved in the polymer matrix to enhance the chain segment lubrication with their long alkyl group but improve the whole chain friction through the formation of nano-eutectics. These polyacrylates undergo multimodal mechanical responses, including temperature- or time-programmed deformation and load-bearing like artificial muscles. This molecular design principle and synthetic method provide a robust platform for the fabrication of ultra-tough polymers for soft robots with multiple customized functions.

Effect of hydrophilic group structure on the properties of fluorinated surfactants with the same hydrophobic skeleton

Fluorinated surfactants are composed of hydrophilic and hydrophobic groups, so the properties of fluorosurfactants are also affected by the combination of these two groups. However, there is little studies on the effect of the structure of hydrophilic groups on the fluorosurfactants properties. This paper reported the synthesis of a novel quaternary ammonium surfactant (BPAF-OH) with branched fluorocarbon short chains. To investigate the effect of hydrophilic group structure on the performance of fluorinated surfactants, the properties of BPAF-OH were compared with two fluorinated surfactants (BPAF-IEt and BPAF-SMA, which have the same hydrophobic skeleton as BPAF-OH). Experimental results had shown that for these three surfactants, the hydrophilic group structures had the relatively small impact on the thermal stability of fluorinated surfactants. In contrast, the hydrophilic group structures had the greater influence on the surface activities: BPAF-OH had the best surface activity with the critical micelle concentration (CMC) of 6.00 × 10−3 mmol/L, and the surface tension (γCMC) of 15.96 mN/m. Furthermore, the hydrophilic group structures had the certain influence on the thermodynamic parameters, aggregation behaviour and wettability of fluorine surfactants.

Impact of hydroxyethyl headgroup on long-chain quaternary ammonium cationic surfactants: Solubility, surface activities, self-assembly behaviors, and rheological properties

The incorporation of hydroxy groups into long-chain quaternary ammonium surfactants can enhance their solubility and confer other desirable properties; however, the systematic investigation on the solution properties and the influence of molecular structures was less documented. In this work, two saturated C18-tailed quaternary ammonium surfactants with dual hydroxyethyl moieties, namely N,N-bis(2-hydroxyethyl)-N-methyloctadecan-1-aminium iodide (HEOAI) and N,N-bis(2-hydroxypropyl)-N-methyloctadecan-1-aminium iodide (HPOAI), were designed and synthesized. We investigated and compared their Krafft temperature (Tk), surface activities, self-assembly behaviors, and rheological properties. Our findings demonstrate that the introduction of hydroxyethyl groups dramatically improves the solubility and surface activities. The Tk of HEOAI and HPOAI is approximately 50 °C lower than that of the corresponding surfactant octadecyl trimethylammonium iodide. Both surfactants exhibit lower critical micelle concentration and equilibrium surface tension compared to those of corresponding conventional quaternary ammonium surfactant. This should be ascribed to the formation of hydrogen bonds between hydroxyl groups and water molecules. Moreover, HPOAI shows even better solubility and surface activities than HEOAI does. Additionally, the presence of two more methyl groups for HPOAI enhances its ability to form worm-like micelles in pure water. However, HEOAI shows better salt and temperature resistance for maintaining stability of worm-like micelles. A solution containing 50 mM HEOAI with 10 % NaCl exhibits temperature tolerance up to around 80 °C, indicating potential application as fracturing fluid for shallow and medium oil/gas reservoirs. These findings contribute to designing surfactants with improved solubility and diverse properties.

Bacterial dealkylation of benzalkonium chlorides in wastewater produces benzyldimethylamine, a potent N-nitrosodimethylamine precursor

N-nitrosodimethylamine (NDMA) is a carcinogenic disinfection byproduct that forms during chloramine disinfection of municipal wastewater effluents which are increasingly used to augment drinking water supplies due to growing water scarcity. Knowledge of wastewater NDMA precursors is limited and the known pool of NDMA precursors has not closed the mass balance between precursor loading, precursor NDMA yield, and formed NDMA. Benzalkonium chlorides (BACs) are the most prevalent quaternary ammonium surfactants and have antimicrobial properties. The extensive utilization of BACs in household, commercial and industrial products has resulted in their detection in wastewater at elevated concentrations. We report the formation of a potent NDMA precursor, benzyldimethylamine (BDMA) from the biodegradation of BACs during activated sludge treatment. BDMA formation and NDMA formation potential (FP) were functions of BAC and mixed liquor suspended solids concentration at circumneutral pH, and the microbial community source. Sustained exposure to microorganisms reduced NDMA FP through successive dealkylation of BDMA to less potent precursors. BAC alkyl chain length (C8 – C16) had little impact on NDMA FP and BDMA formation because chain cleavage occurred at the C–N bond. Wastewater effluents collected from three facilities contained BDMA from 15 to 106 ng/L, accounting for an estimated 4 to 38 % of the NDMA precursor pool.

Interaction, Surface Activity, and Application of Mixed Systems of Alcohol Ether Sulfate Anionic Surfactants with Multiple Ethylene Oxide Groups and Gemini Quaternary Ammonium Surfactant.

The surface activities and application properties for the mixtures of cationic surfactants tetramethylene-1,4-bis[N,N-bis(hydroxypropyl)-hexa/decyloxypropylammonium] bromide (GC10-P) and tetramethylene-1,4-bis[N,N-bis(hydroxyethyl)-hexa/decyloxypropylammonium] bromide (GC10-E) and anionic surfactant isomeric sodium fatty alcohol ether sulfates (iso-AE9S) were investigated using both the tensiometry and the conductometry. The interaction parameters and thermodynamic micellization parameters of GC10-P/iso-AE9S and GC10-E/iso-AE9S mixtures were evaluated by Clint-Rubingh and Motomura theoretical models. When the mole fraction of α1 for GC10-P/iso-AE9S mixed system was 0.2, the critical micelle concentration (CMC) reached a minimum of 1.61 × 10-4 mol/L, and the minimum critical micelle concentration of the GC10-E/iso-AE9S mixed system is 2.67 × 10-5 mol/L at α1 = 0.6. The CMC value of the mixed system is 1-2 orders of magnitude lower than that of any single component. The results indicate that the synergistic effects of the investigated mixed systems (evaluated by βm) are in order of GC10-P/iso-AE9S < GC10-E/iso-AE9S, with maximum βm values of -17.98 and -9.78, respectively. The change in zeta potential indicates that the poly(ethylene oxide) chain has weakened the charge density of the hydrophilic headgroup of the anionic surfactant. The interfacial tension at the oil-water interface in the mixed system of anionic/cationic surfactants is lower than that of any single component, exhibiting a higher interfacial activity. The mixed system exhibits a decreased contact angle and superior wetting ability over any single component, and it also enhances foam performance, emulsification performance, and degreasing performance.

Polycomplexes to modulate bactericidal activity of cetylpyridinium bromide

Cetylpyridinium bromide, a quaternary ammonium surfactant, was electrostatically complexed with an excess of anionic polymers such as biodegradable sodium alginate or non-biodegradable sodium polyacrylate. The binding of surfactant with alginate delivered polymer–surfactant complexes capable of killing both more surfactant-sensitive Escherichia coli and less surfactant-sensitive Pseudomonas aeruginosa bacteria, while the binding with acrylate gave complexes active only against Escherichia coli. The results obtained show a way for adjustment of the antimicrobial formulation to a specific pathogen to be destroyed.

Influence of pH on spectroscopic and interfacial features of phenol in aqueous cetrimonium bromide solutions of different concentrations

Phenol is an aromatic compound with toxic effects on the environment and living organisms. Cetrimonium bromide (CTAB) is a cationic, quaternary ammonium surfactant, constituent in industrial formulations, and is employed for solubilization as well as removal of pollutants. This study explores the impact of pH on the behavior of phenol in the micellar solution of CTAB via UV–Visible spectroscopy and surface tension measurements at room temperature. Binding coefficient (Kb), free energy change of binding (ΔGb), change in molar absorptivity (Δε), partition coefficient (Kc), free energy change of partitioning (ΔGp) and number of molecules per micelle (n) were determined at different pH. Results showed that phenol exhibits no appreciable interaction with the CTAB, however phenolate ions have the tendency to bind with CTAB micelles and penetrate in the palisade layer of CTAB.Surface properties such as surface excess (τmax), minimum area per molecule (Amin), packing parameter (P), surface area per head group (as), free energy changes of micellization (ΔGm), adsorption ΔGads, and transfer (ΔGtrans), and surface pressure (Π) for CTAB, and phenol in CTAB solutions were also determined. Interfacial studies supported the role of phenol in facilitating micellization of CTAB thermodynamically and hence a fall in CMC values of CTAB except for pH 7.11. Calculated interfacial parameters established the influence of phenol over rearrangement and surface adsorption of CTAB molecular ions at air/water interface. Surface tension results also showed that unionized phenol molecules have low surface activity (62.23mN/m), but when phenol is ionized into phenolate ion surface dramatically increased (44.17 mN/m).

Preparation of novel shell-ionotropically crosslinked micelles based on hexadecylamine and tripolyphosphate for cancer drug delivery

Aims Micellar systems have the advantage of being easily prepared, cheap, and readily loadable with bioactive molecular cargo. However, their fundamental pitfall is poor stability, particularly under dilution conditions. We propose to use simple quaternary ammonium surfactants, namely, hexadecylamine (HDA) and hexadecylpyridinium (HDAP), together with tripolyphosphate (TPP) anion, to generate ionotropically stabilized micelles capable of drug delivery into cancer cells. Methods optimized mixed HDA/HDAP micelles were prepared and stabilized with TPP. Curcumin was used as a loaded model drug. The prepared nanoparticles were characterized by dynamic light scattering, infrared spectroscopy, transmission electron microscopy, and differential scanning calorimetry. Moreover, their cellular uptake was assessed using flow cytometry and confocal fluorescence microscopy. Results The prepared nanoparticles were found to be stable under dilution and at high temperatures and to have a size range from 139 nm to 580 nm, depending on pH (4.6-7.4), dilution (up to 100 times), and temperature (25 – 80 °C). They were effective at delivering their load into cancer cells. Additionally, flow cytometry indicated the resulting stabilized micellar nanoparticles to be non-cytotoxic. Conclusions The described novel stabilized micelles are simple to prepare and viable for cancer delivery.

Modified cellulose nanocrystals enhanced polycaprolactone multifunctional films with barrier, UV-blocking and antimicrobial properties for food packaging

The packaging industry demands improved eco-friendly materials with new and enhanced properties. In this context, bio-nanocomposite films with antimicrobial and UV-shielding properties based on modified cellulose nanocrystals/polycaprolactone (MCNC/PCL) were fabricated via solution casting method, and then food packaging simulation was carried out. CNCs were obtained by acid hydrolysis followed by successful functionalization with Quaternary ammonium surfactant, confirmed by FTIR, XPS, XRD, TEM, and DLS analyses. Furthermore, the morphological, physical, antibacterial, and food packaging properties of all prepared films were investigated. Results showed that the mechanical, UV blocking, barrier properties, and antibacterial activity of all composite films were remarkably improved. Particularly, the addition of 3 wt% MCNC increased the tensile strength and elongation at break by 27.5 % and 20.0 %, respectively. Moreover, the permeability of O2, CO2, and water vapor dramatically reduced by 97.6 %, 96.7 %, and 49.8% compared to the Neat PCL. Further, the UV-blocking properties of the composite films were significantly improved. The antimicrobial properties of MCNC/PCL films showed good antimicrobial properties against S. aureus. Finally, cherry packaged with 1 and 3 wt% MCNC films exhibited satisfactory freshness after 22 days of preservation. Overall, the fabricated PCL nanocomposite films can be utilized in the food packaging industry.

Heparin-network-mediated long-lasting coatings on intravascular catheters for adaptive antithrombosis and antibacterial infection

Bacteria-associated infections and thrombosis, particularly catheter-related bloodstream infections and catheter-related thrombosis, are life-threatening complications. Herein, we utilize a concise assembly of heparin sodium with organosilicon quaternary ammonium surfactant to fabricate a multifunctional coating complex. In contrast to conventional one-time coatings, the complex attaches to medical devices with arbitrary shapes and compositions through a facile dipping process and further forms robust coatings to treat catheter-related bloodstream infections and thrombosis simultaneously. Through their robustness and adaptively dissociation, coatings not only exhibit good stability under extreme conditions but also significantly reduce thrombus adhesion by 60%, and shows broad-spectrum antibacterial activity ( > 97%) in vitro and in vivo. Furthermore, an ex vivo rabbit model verifies that the coated catheter has the potential to prevent catheter-related bacteremia during implantation. This substrate-independent and portable long-lasting multifunctional coating can be employed to meet the increasing clinical demands for combating catheter-related bloodstream infections and thrombosis.

Oil and Organic Liquids Incorporation into Fresh Geopolymer Pastes Using Suitable Quaternary Ammonium Surfactants.

The direct incorporation of low viscosity organic liquids (OL) such as dodecane and tributylphosphate (TBP) into fresh geopolymers (GP) is difficult and generally leads to variable amounts of un-incorporated OL remaining outside the hardened geopolymer. Experimentally, it is observed that a regular torque increase during OL incorporation corresponds to a suitable dispersion of the OL in the form of fine micrometric droplets. This can be obtained for TBP and dodecane by adding a small quantity of quaternary ammoniums salts (QAs) such as cetyltrimethylammonium bromide (CTAB). Shorter alkyl chains QAs, such as hexamethyltrimethylammonium (HMTA) can also be used but with a reduced efficiency. The positive impact of CTAB is then confirmed by the Washburn capillary rise method, showing that the interactions between TBP and CTAB-modified metakaolin are weaker compared to untreated powder. Finally, it is observed that the incorporation of TBP into geopolymer slurries is much easier than the incorporation of dodecane. The low interfacial tension measured between TBP and the activating solution (around 8 mN·m -1 ), contrasting with dodecane (29 mN·m -1 ), explains that the dispersion of TBP droplets in fresh metakaolin suspensions is more efficient.

Gemini Quaternary Ammonium Surfactants with Different Counterions-modified Montmorillonite for Efficient Removal of Methyl Orange.

Organic Na-montmorillonite (OMt-12-2-12·2Y - , Y=CH 3 CO 3 - , C 6 H 5 COO - and Br - ) modified by a series of Gemini quaternary ammonium surfactants with different counterions was prepared for enhancing the adsorption capacity of methyl orange. Compared with the initial adsorption capacity of 5.251 mg/g of Na-Mt, the adsorption effect of OMts under the optimal conditions increased by about 31~34 times. The adsorption isotherms and kinetics of all adsorption processes were respectively described by Langmuir and pseudo-second-order models. The structure, hydrophobicity and hydration of the counterions, as well as the affinity of the counterions with the long aliphatic chains, had a certain influence on the adsorption performance of OMts for methyl orange.

Evaluation of the Antitumor Activity of Quaternary Ammonium Surfactants.

Quaternary ammonium surfactants, due to their diverse chemical structure and their biological properties, can be used in medicine as DNA carriers, disinfectants, and antimicrobial and antitumor agents. In this study, using melanoma A375, colon adenocarcinoma HT-29 and normal human dermal fibroblast (NHDF) cells, we tested the hypothesis that the quaternary ammonium surfactants 2-dodecanoyloxyethyl)trimethylammonium bromide (DMM-11), 2-dodecanoyloxypropyl)trimethylammonium bromide (DMPM-11) and 2-pentadecanoyloxymethyl)trimethylammonium bromide (DMGM-14) act selectively against cancer cells. The results showed that these compounds led to the initiation of the apoptotic process of programmed cell death, as evidenced by the ratio of the relative expression of Bax protein to Bcl-2. The encapsulation of surfactants in liposomes allowed lower concentrations to be used. Moreover, encapsulation reduced their toxicity towards non-cancerous cells. The anticancer efficiency and apoptotic effect of the liposomal formulations with surfactants (DMM-11, DMPM-11 and DMGM-14) were higher than those of surfactant-free liposomes. Therefore, quaternary ammonium surfactant-loaded liposomes show significant potential as delivery vehicles for the treatment of melanoma and colon cancers. The use of nano-formulations offers the advantage of optimizing quaternary ammonium surfactant delivery for improved anticancer therapy.

N‐(4‐Chloromethylbenzyl)‐N, N‐dimethyldodecan‐1‐aminium Chloride: A Quaternary Ammonium Surfactant as Corrosion Inhibitor

AbstractThis study used a quaternary surfactant, N‐(4‐Chloromethylbenzyl)‐N, N‐dimethyldodecan‐1‐aminium chloride (CMBDAC), as an excellent corrosion inhibitor of C1018 carbon steel (C1018 CS) in harsh 15 % HCl acidizing condition. CMBDAC was synthesized with an excellent yield and characterized by NMR, FTIR, and TGA. Gravimetric weight loss (WL), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) studies were employed to measure the efficacy of CMBDAC. At a relatively low concentration of 15 ppm, CMBDAC surpassed 90 % inhibition efficiency, with a maximum inhibition efficiency of 99.25 % being reached just for 50 ppm of CMBDAC. The inhibitor showed an efficacy of 96.16 % even at a temperature of 60 °C via the WL technique, showing potential to be used as a high‐temperature corrosion inhibitor. The adsorption isotherm study revealed that CMBDAC followed Langmuir adsorption isotherm. The Gibbs free energy of adsorption ( was calculated to be −40.43 kJ mol−1, indicating that CMBDAC was adsorbed via chemisorption. A very high value (1.68×105 L mol−1) of equilibrium constant ( ) suggested very strong adsorption of the inhibitor. PDP study disclosed that CMBDAC acted as a mixed‐type inhibitor. SEM‐EDX study demonstrated the adsorption of CMBDAC on the C1018 surface. Different DFT‐optimized parameters have been discussed in detail to support the superb inhibitory action indicated by CMBDAC.

Design of cationic surfactant reinforced carrageenan waterproof composite films and applied as water induced electricity generator

Carrageenan (CR) is a renewable polysaccharide material for packaging application due to its good film-forming property, but its use can be limited by the water solubility. In this research, CR hydrogels were modified by quaternary ammonium surfactants with different length of hydrocarbon tails (n, 8≦n≦16) by adsorption method and waterproof films were obtained after drying. The composition and charge interaction of composite films was confirmed by FTIR. Both thermogravimetric analysis and energy dispersive spectrometer indicated that the surfactant ions replaced K+ to form complexes with CR. The X-ray diffraction revealed the decreased amorphous nature of composite films compared to neat CR film. Water-related physical properties, such as water content, weight percentage change after contact with water, water vapor transmission, and water contact angle were intimately related to n. When 8≦n≦14, the waterproof properties were enhanced with the increase of n. Meanwhile, the waterproof property of composite film was ascertained by the no leakage result in the boiling water packaging experiment. When n = 16, sandwich structure was found in the sectional micromorphology images, and water bag structure formed after immersed into water. By comparing the mechanical properties of the composite films in different condition, we found that quaternary ammonium surfactants improved significantly the tensile strength in water and increased elongation at break in dry state. The composite films can be used as water induced voltage generator for their polyelectrolyte nature. Benefiting from the high stability of the composite films in water, their water-induced voltage generation process had good recyclability. Due to the antimicrobial activity of the quaternary ammonium salts and the waterproof property, composite films were more stable and degraded more slowly than neat CR film in nature environment.

Antiviral efficacy of nanomaterial-treated textiles in real-life like exposure conditions

Due to the growing interest towards reducing the number of potentially infectious agents on critical high-touch surfaces, the popularity of antimicrobially and antivirally active surfaces, including textiles, has increased. The goal of this study was to create antiviral textiles by spray-depositing three different nanomaterials, two types of CeO2 nanoparticles and quaternary ammonium surfactant CTAB loaded SiO2 nanocontainers, onto the surface of a knitted polyester textile and assess their antiviral activity against two coronaviruses, porcine transmissible gastroenteritis virus (TGEV) and severe acute respiratory syndrome virus (SARS CoV-2). Antiviral testing was carried out in small droplets in semi-dry conditions and in the presence of organic soiling, to mimic aerosol deposition of viruses onto the textiles. In such conditions, SARS CoV-2 stayed infectious at least for 24 h and TGEV infected cells even after 72h of semi-dry deposition suggesting that textiles exhibiting sufficient antiviral activity before or at 24 h, can be considered promising. The antiviral efficacy of nanomaterial-deposited textiles was compared with the activity of the same nanomaterials in colloidal form and with positive control textiles loaded with copper nitrate and CTAB. Our results indicated that after deposition onto the textile, CeO2 nanoparticles lost most of their antiviral activity, but antiviral efficacy of CTAB-loaded SiO2 nanocontainers was retained also after deposition. Copper nitrate deposited textile that was used as a positive control, showed relatively high antiviral activity as expected. However, as copper was effectively washed away from the textile already during 1 h, the use of copper for creating antiviral textiles would be impractical. In summary, our results indicated that antiviral activity of textiles cannot be predicted from antiviral efficacy of the deposited compounds in colloid and attention should be paid on prolonged efficacy of antivirally coated textiles.

Self-Aggregation, Antimicrobial Activity and Cytotoxicity of Ester-Bonded Gemini Quaternary Ammonium Salts: The Role of the Spacer.

Five ester-bonded gemini quaternary ammonium surfactants C12-En-C12 (n = 2, 4, 6), with a flexible spacer group, and C12-Bm-C12 (m = 1, 2), with rigid benzene spacers, were synthesized via a two-step reaction and analyzed. Furthermore, the effects of the spacer structure, spacer length and polymerization degree on the self-aggregation, antimicrobial activity and cytotoxicity of C12-En-C12 and C12-Bm-C12 and their corresponding monomer N-dodecyl-N,N,N-trimethyl ammonium chloride DTAC were investigated. The results showed that C12-En-C12 and C12-Bm-C12 had markedly lower critical micellar concentration (CMC) values and lower surface tension than DTAC. Moreover, the CMC values of C12-En-C12 and C12-Bm-C12 decreased with increasing spacer length. In the case of equivalent chain length, the rigidity and steric hindrance of phenylene and 1,4-benzenediyl resulted in larger CMC values for C12-Bm-C12 than for C12-En-C12. The antibacterial ability of C12-En-C12 and C12-Bm-C12 was assessed using Escherichia coli (E. coli) and Staphylococcus albus (S. aureus) based on minimum inhibitory concentrations (MICs). Furthermore, C12-En-C12 and C12-Bm-C12 exhibited higher antimicrobial activity than DTAC and had stronger function toward S. aureus than E. coli. The antimicrobial activity was enhanced by increasing the spacer chain length and decreased with the increased rigidity of the spacers. The cytotoxic effects of C12-En-C12 and C12-Bm-C12 in cultured Hela cells were evaluated by the standard CCK8 method based on half-maximal inhibitory concentration (IC50). The cytotoxicity of C12-En-C12 and C12-Bm-C12 was significantly lower than alkanediyl-α,ω-bis(dimethyldodecylammonium) bromide surfactants and DTAC. The spacer structure and the spacer length could induce significant cytotoxic effects on Hela cells. These findings indicate that the five ester-bonded GQASs have stronger antibacterial activity and lower toxicity profile, and thus can be used in the pharmaceutical industry.

Formulation and Evaluation of Prednisolone Sodium Metazoate-Loaded Mucoadhesive Quatsomal Gel for Local Treatment of Recurrent Aphthous Ulcers: Optimization, In Vitro, Ex Vivo, and In Vivo Studies.

This study aims to formulate a buccal mucoadhesive gel containing prednisolone sodium metazoate-loaded quatsomes for efficient localized therapy of recurrent aphthous ulcers. Quatsomes were prepared using a varied concentration of quaternary ammonium surfactants (QAS) and cholesterol (CHO). A 23 factorial design was conducted to address the impact of independent variables QAS type (X1), QAS to CHO molar ratio (X2), and sonication time (X3). The dependent variables were particle size (PS; Y1), polydispersity index (PDI; Y2), zeta potential (ZP; Y3), entrapment efficiency percent (EE%; Y4) and percent of drug released after 6 h (Q6%: Y5). Then, the selected quatsomes formula was incorporated into different gel bases to prepare an optimized mucoadhesive gel to be evaluated via in vivo study. The PS of the developed quatsomes ranged from 69.47 ± 0.41 to 113.28 ± 0.79 nm, the PDI from 0.207 ± 0.004 to 0.328 ± 0.004, ZP from 45.15 ± 0.19 to 68.1 ± 0.54 mV, EE% from 79.62 ± 1.44 to 98.60% ± 1.22 and Q6% from 58.39 ± 1.75 to 94.42% ± 2.15. The quatsomal mucoadhesive gel showed rapid recovery of ulcers, which was confirmed by the histological study and the evaluation of inflammatory biomarkers. These results assured the capability of the developed quatsomal mucoadhesive gel to be a promising formulation for treating buccal diseases.

Revealing foam stability for cationic and zwitterionic triethylsilyl-containing surfactants

A fundamental understanding of surfactant structure–property–performance relationships will inform the design of next-generation alternatives to perfluoroalkyl substances (PFAS) in aqueous film-forming foams. This manuscript describes the synthesis, solution properties, and foam stability of novel triethylsilyl-containing surfactants, which elucidated the influence of the hydrophilic head group on critical micelle concentration (CMC), surface tension, and foam stability. Photocatalyzed hydrosilylation of triethylsilane and N,N-dimethyl allylamine yielded N,N-dimethyl-3-(triethylsilyl)propane-1-amine. Subsequent functionalization with either propane sultone or bromoethane afforded zwitterionic sulfobetaine surfactant, 3-(dimethyl(3-(triethylsilyl)propyl)ammonio)propane-1-sulfonate (TESDMAPS) and cationic quaternary ammonium surfactant, and N-ethyl-N,N-dimethyl-3-(triethylsilyl)propane-1-ammonium bromide (TESDMABr), respectively. Dynamic light scattering and cryo-transmission electron microscopy (TEM) characterized micelle size and shape in solutions above the CMC. Surface tensiometer analysis determined minimum TESDMAPS and TESDMABr solution surface tensions of 37.7 and 35.9 mN/m, respectively. Molecular dynamics simulations related this decrease in surface tension to a larger average interfacial area of 88 Å2 per TESDMABr molecule compared to 66 Å2 per TESDMAPS molecule. Steady-shear rheological measurements showed consistent exponential viscosity-scaling relationships between TESDMAPS and TESDMABr solutions ≤ 30 wt. %. Above this concentration, TESDMAPS displayed solution viscosities greater than TESDMABr, and a mixture of surfactants provided an intermediate concentration dependent viscosity scaling. Dynamic foam analysis revealed TESDMABr foams displayed longer 25% foam drainage times than TESDMAPS. The oscillatory rheology of TESDMABr solutions demonstrated solid-like solution behavior at low shear rates. Finally, polarized light-imaging rheology highlighted the formation of birefringent structures in TESDMABr solutions under shear. For the first time, this work relates solution viscoelasticity from shear-induced surfactant assembly to foam stability with implications on fluorine-free, next-generation, fire-fighting foams.

Experimental and DFT investigations on the influence of cetrimonium bromide (CTAB) on surface morphology and anti-tarnishing performance of pulse galvanostatically deposited gold coatings from a cyanide-free electroplating solution

In the present study, pulse galvanostatic electroplating method is used to produce mirror-bright gold (Au) deposits from a non-cyanide electroplating solution. Electrodeposition is carried out from two different solutions in the presence and absence of cetrimonium bromide (CTAB) to study the influence of the quaternary ammonium surfactant on the microstructure and the anti-tarnishing behaviour of the Au deposits. Electrochemical studies (cyclic voltammetry (CV) and chronoamperometry) are carried out to get an insight into the type of nucleation and growth occurring during the electrodeposition of gold. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies show that in the presence of CTAB, fine-structured coating with a compact and uniform morphology is obtained. The X-ray diffraction (XRD) studies show that in the presence of cetrimonium bromide, the growth of Au is favoured along the (111) lower index crystal surface, and with no cetrimonium bromide in the electroplating bath, the growth of Au is favoured along the (200) higher index crystal surface. The influence of cetrimonium bromide on the resistance to the tarnishing of the Au coating is initially predicted by quantum chemical calculations based on density functional theory (DFT). Electrochemical impedance spectroscopy (EIS) and static immersion test also confirm the less severity of tarnishing for the coating electrodeposited from the solution containing cetrimonium bromide (CTAB). Visual observation and the glossiness analysis confirm the difference in the physical appearance of the coating surface in the as-deposited condition and after tarnishing. The findings of this study demonstrate that the electrodeposition of Au with a crystal surface control, by using CTAB as a bath additive, can be used as a plausible technique for enhancing the anti-tarnishing performance of the coatings.