Amine Salts Research Articles

Synthesis of 2-aminopropyl benzopyran derivatives as potential agents against triple-negative breast cancer.

Synthesis of three series of 2-aminopropyl derivatives containing a benzopyran nucleus was performed to evaluate their performance against triple-negative breast cancer cell lines (MDA-MB-231 and MDA-MB-436) and normal breast epithelial cells (MCF10A). For the three series, the cytotoxic activity was as follows: N-methylated derivatives (tertiary amines) 5b, 6b, and 7b > secondary amine benzopyrans 5, 6, and 7 > quaternary amine salts 5c, 6c, and 7c > free phenolic derivatives 5a, 6a, and 7a. The structure-activity relationship showed the importance of the presence of an amine group and a p-fluorobenzyloxy substituent in the chromanol ring (IC50 values from 1.5 μM to 58.4 μM). In addition, 5a, 5b, 6a, and 7b displayed slight selectivity towards tumor cells. Compounds 5, 5a, 5b, 6, 6a, 6c, 7, and 7b showed apoptotic/necrotic effects due to, at least in part, an increase in reactive oxygen species generation, whereas 5b, 5c, 6b, 7a, and 7c caused cell cycle arrest in the G1 phase. Further cell-based mechanistic studies revealed that 5a, 6a, and 7b, which were the most promising compounds, downregulated the expression of Bcl-2, while 5b downregulated the expression of cyclins CCND1 and CCND2. Therefore, 2-aminopropyl benzopyran derivatives emerge as new hits and potential leads for developing useful agents against breast cancer.

Omnidirectional diffusion of organic amine salts assisted by ordered arrays in porous lead iodide for two-step deposited large-area perovskite solar cells

The porous lead iodide layer with ordered arrays structure is firstly fabricated to facilitate the omnidirectional diffusion of organic amine salts and realize high quality large-area perovskite film in two-step sequential deposition.

Synthesis and anti-bacterial/fungal activities of amphiphilic polysiloxanes primary ammonium salts

Amphiphilic cationic polymers are currently used as antimicrobial agents to disrupt microbial membranes with long-termed stability and low bio-toxicity. However, there are few studies on the relationship between molecular structure and antimicrobial properties of amphiphilic polymers containing primary amine salts against fungi. In this work, a series of polysiloxanes graft primary ammonium salts (PDMS-g-AH) with tunable molecular weights (3 kDa, 5 kDa, 8 kDa, and 10 kDa) and grafting ratios (50% and 75%) were synthesized via thiol-ene “click reaction”, and the effect of their structural parameters on the broad-spectrum inhibition of bacteria (Escherichia coli and Staphylococcus albus) and pathogenic fungi (Candida albicans), especially on two phytopathogenic fungi (Fusarium oxysporum f. sp. cubense race 4 (Foc4) and Rhizoctonia solani (R. solani)) were systematically assessed. The aggregation of polymers in water was characterized by the critical micelle concentration (CMC) values, zeta potentials, and particle sizes and distributions. All PDMS-g-AH had positive zeta-potential values and exhibited high micellar stability in water. At the same time, the aggregation characteristics of polymers are affected by the structure and molecular weight of polymers. Small aggregates and high zeta-potentials interacted easily with the microbial cell membranes, which affected the antimicrobial activity together. These results indicated that the block type of PDMS-g-AH, i.e., PDMS-b-AH, showed better antimicrobial activities than the random type (PDMS-co-AH), and the optimal antimicrobial activities were obtained for moderate polymer chain length (about 5 kDa). This work reveals the relationship between the chemical structure of PDMS-g-AH, their aggregation behavior in water as well as interaction with biological membranes during the sterilization process, which provides the potential applications as fungicidal agents for effectively controlling plant diseases, such as rice sheath blight and banana Fusarium wilt.

Non-invasive optical characterization and detection of CA 15-3 breast cancer biomarker in blood serum using monoclonal antibody-conjugated gold nanourchin and surface-enhanced Raman scattering.

A proof-of-concept of colloidal surface-enhanced Raman scattering (SERS) substrate for rapid selective detection of overexpressed CA 15-3 biomarker in breast cancer serum (BCS) is suggested using PEGylated gold nanourchins (GNUs) conjugated with anti-CA 15-3 monoclonal antibody (mAb). UV-vis spectroscopy provided conformational information about mAb where the initial aromatic amino acid peak was red-shifted from 271 to 291nm. The fluorescence peak of tyrosine in mAb was reduced by ≈ 77%, and red-shifted by ≈ 3nm after incubation in BCS. Fourier transform near-infrared spectroscopy and SERS were used to study the composition and the molecular structure of the mAb and BCS. Some of the most dominant Raman shifts after GNU-PEG-mAb interaction with BCS are 498, 736, 818, 1397, 1484, 2028, 2271, and 3227cm-1 mainly corresponding to C-N-C in amines, vibrational modes of amino acids, C-H out-of-plane bend, C-O stretching carboxylic acid, the vibrational mode in phospholipids, NH3+ amine salt, C≡N stretching in nitriles, and O-H stretching. The intensity of SERS signals varied per trial due to the statistical behavior of GNU in BCS, agglomeration, laser power, and the heating effect. Despite very small amount of plasmonic heating, the result of the ANOVA test demonstrated that under our experimental conditions, the heating effect on signal variation is negligible and that the differences in the laser power are insignificant for all SERS observations (p > 0.6); thus, other parameters are responsible. The absorbance of mAb-conjugated GNU was decreased after five minutes of irradiation at 8 mW in the BCS.

Towards a rational design of natural deep eutectic solvents for the extraction of polyphenols from Luma apiculata

In this article, we present a complementary experimental and theoretical study for designing a task-specific medium for the ultrasound extraction of polyphenols ofLuma apiculata. Our results reveal that choline chloride-based DESs are suitable candidates as extraction media. To capture the role of the solvent in the extraction process, we employed molecular dynamics simulation of a model solute surrounded by different DESs. Results showed that an adequate DES should have an organic acid, an amine or quaternary ammonium salt, a content of water for the formation of the eutectic mixture, and an acidic anion. The importance and role of each component could be rationalized by their synergetic solvation of the polyphenols.

Regulating Alkyl Chain Length on Quaternization TiO2 for Boosting Photocatalytic Performance: Synergism of Promoting Photogenerated Charge Separation and Improving Reactant Adsorption.

To explore the effect of surface charge properties of a photocatalyst on photocatalytic activity, quaternization TiO2 particles with different alkyl chain lengths (CT-X/P25) are first synthesized to boost the photocatalytic activity. The effect of a quaternary ammonium group with different alkyl chain lengths on the photocatalytic activity of CT-X/P25 is investigated. Interestingly, the introduction of a quaternary ammonium group on CT-X/P25 not only contributes to improving the photodegradation efficiency of anionic dyes due to enhancing of adsorption capacity through electrostatic attraction, but also it can improve the photodegradation efficiency of cationic dyes. Therefore, there seems to be another factor affecting the photocatalytic activity. The results of photoelectric characterization show that the photogenerated charge separation of CT-X/P25 is greatly enhanced, which is beneficial to improve the photocatalytic activity. Simultaneously, the results show that the difference in the photocatalytic activity of CT-X/P25 is mainly related to the charge intensity of -N+(CH3)2- in the quaternary amine salt. According to X-ray photoelectron spectroscopy, the charge intensity of -N+(CH3)2- in CT-X/P25 gradually increases with the increase in alkyl chain lengths, which is conducive to promoting photogenerated charge separation and improving the adsorption for anionic dyes. The photocatalytic activity has been further enhanced due to the enhancement of this synergy. In summary, the quaternary ammonium salt-modified CT-X/P25 shows an excellent synergistic effect on the process of photodegradation of anionic dyes: promoting photogenerated charge separation and adsorption.

ANTIMICROBIAL PROPERTIES OF ACETYLENE QUATERNARY AMMONIUM SALTS

For a long period of time, saturated quaternary ammonium salts have been used as components of compositions that have antimicrobial properties against certain strains of microorganisms. The disadvantage of using such compositions is the formation of resistance of some microorganisms to the latter. Thus, it seems relevant to create antimicrobial compositions based on components with which microorganisms had no contact in the environment. This article presents the results of experimental studies of the antimicrobial activity of synthesized acetylenic quaternary ammonium salts, salts of tertiary amines, as well as commercially available saturated quaternary ammonium salts in relation to test cultures of Proteus mirabilis , Proteus vulgaris , Salmonella typhimurium , Pseudomonas aeruginosa , Escherichia coli , Shigella sonne , Serratia marcescens , Staphylococcus aureus , Candida albicans , Saccharomyces cerevisiae , Penicillium spp . and Bacillus cereus . The diameter of the zones of inhibition of growth by test-cultures of microorganisms was determined by the disk-diffusion method. The action of solutions of acetylenic quaternary ammonium salts of various concentrations was carried out by the method of serial dilutions. The minimum inhibitory concentration of solutions of acetylenic quaternary ammonium salts has been determined. The research results showed that the range of the minimum inhibitory concentration of tri-n-octylprop-2-ynylammonium bromide for the studied test cultures of microorganisms is from 0.1 to 0.0001%, and bromides of tri-n-octylbut-2-ynyl- and tri-n-octyloct -2-ynylammonium - from 1 to 0.0001%, while limiting quaternary ammonium salts exhibit an antimicrobial effect on similar cultures of pathogenic microorganisms at concentrations an order of magnitude higher and more. Thus, solutions of acetylenic quaternary ammonium salts can be promising antimicrobial agents.

Deaminative Arylation and Alkenyaltion of Aliphatic Tertiary Amines with Aryl and Alkenylboronic Acids via Nitrogen Ylides

AbstractTransition‐metal‐catalyzed Suzuki–Miyaura coupling has significantly advanced C−C bond formation and has been well recognized in organic synthesis, pharmaceuticals, materials science and other fields. In this rapid development, cross coupling without transition metal catalyst is a big challenge in this field, and using widely existing tertiary amines as electrophiles to directly couple with boronic acids has great hurdles yet significant application prospects. Herein, we report an efficient and general deaminative arylation and alkenylation of tertiary amines (propargyl amines, allyl amines and 1H‐indol‐3‐yl methane amines) with ary and alkenylboronic acids enabled by difluorocarbene under transition‐metal‐free conditions. Preliminary mechanism experiments suggest that in situ formed difluoromethyl quaternary amine salt, nitrogen ylide and tetracoordinate boron species are the key intermediates, the subsequent 1,2‐metallate shift and protodeboronation complete the new coupling reaction.

Deaminative Arylation and Alkenyaltion of Aliphatic Tertiary Amines with Aryl and Alkenylboronic Acids via Nitrogen Ylides.

Transition-metal-catalyzed Suzuki-Miyaura coupling has significantly advanced C-C bond formation and has been well recognized in organic synthesis, pharmaceuticals, materials science and other fields. In this rapid development, cross coupling without transition metal catalyst is a big challenge in this field, and using widely existing tertiary amines as electrophiles to directly couple with boronic acids has great hurdles yet significant application prospects. Herein, we report an efficient and general deaminative arylation and alkenylation of tertiary amines (propargyl amines, allyl amines and 1H-indol-3-yl methane amines) with ary and alkenylboronic acids enabled by difluorocarbene under transition-metal-free conditions. Preliminary mechanism experiments suggest that in situ formed difluoromethyl quaternary amine salt, nitrogen ylide and tetracoordinate boron species are the key intermediates, the subsequent 1,2-metallate shift and protodeboronation complete the new coupling reaction.

Synthesis of hybrid peptides from unnatural aminoacids

Hexa peptide 10 has been prepared by the condensation of tetrapeptide acid and dipeptide amine by using standard coupling reagents EDCI, HOBT and DIPEA. In the same method, terta peptide 8 has also been prepared from the acid of dipeptide 6 and amine salt of dipeptide 7 in dichloromethane. Dipeptide 5 has been prepared from the unnatural amino acid which is prepared from d-Glucose and Xyloses. NMR spectral data of peptides indicates presence of secondary structure in peptides.

Investigation of Transport Processes through Ion-Exchange Membranes Used in the Production of Amines from Their Salts Using Bipolar Electrodialysis.

The influence of the nature of amine solutions on the frequency spectrum of the electrochemical impedance of the bipolar membrane aMB-2m is investigated. Moreover, the effect of the circulation rate of solutions in the electrodialyzer chambers on the volt-ampere characteristics of the Ralex AMH and MA-40L anion-exchange membranes and the aMB-2m bipolar membrane has been investigated. The diffusion characteristics of various types of anion-exchange membranes in a system containing dimethylammonium sulfate ((DEA)2H2SO4), as well as the diffusion characteristics of the Ralex AMH membrane in systems with methylammonium sulfate, dimethylammonium sulfate, diethylammonium sulfate, and ethylenediammonium sulfate ((MA)2H2SO4, (DMA)2H2SO4, (DEA)2H2SO4, EDAH2SO4) have been studied. It is shown that diffusion permeability depends on the structure and composition of anion-exchange membranes, as well as on the nature of amines. The technical and economic characteristics of the electromembrane processes for the production of amines and sulfuric acid from amine salts are determined. It is shown that when using Ralex AMH anion-exchange membranes in an electrodialyzer together with bipolar aMB-2m membranes, higher concentrations of diethylamine and sulfuric acid are achieved, compared with the use of MA-40L anion-exchange membranes.

The influence of herbicides and their combination on the development and yield in maize hybrid Knezha 613

In 2018 and 2019 an experiment was conducted using the block method with 12 herbicides in the experimental field of the Maize Research Institute – Knezha. The studies were performed with a maize hybrid Knezha 613 – group 500-600 by FAO, cultivated without irrigation. We studied 8 systems of herbicides which included 6 soil preparations: Adengo 465 SK (isoxaflutole) at a dose of 350 ml/ha; Merlin Flex 480 SK (isoxaflutole) at a dose of 420 ml/ha; Spectrum (dimetenamid – P) at a dose of 1400 ml/ha; Gardoprim plus gold (S-metolachlor + terbutilazin) at a dose of 4500 ml/ha; Dual Gold 960 EK (S-metolachlor) at a dose of 1500 ml/ha and Stomp NEW 330 EK (pendimetalin) at a dose of 4000 ml/ha. The studies included foliar preparations, applied in a phase fourth-fifths leaf of the crop, after the soil ones: Elumis OD (nicoslfuron + mesotrion) at a dose of 2000 ml/ha; Aminopielik 600 SL (2,4-D amine salt) at a dose of 1200 ml/ha; Lumax (S-metolachlor + terbutilazin + mesotrion) at a dose 3000 ml/ha; Matоn 600 EK (2,4-D ester) at a dose of 1100 ml/ha; Laudis OD (tembotrione) at a dose of 2000 ml/ha. Under the test conditions, the herbicidal system Dual gold 960 EK at a dose of 1500 ml/ha and Elumis OD et a dose of 2000 ml/ha is the most efficient: destroying 94.8% (2018) and 94.4 (2019) of the common weeds.

Conductive Passivator for Efficient Monolithic Perovskite/Silicon Tandem Solar Cell on Commercially Textured Silicon

AbstractMonolithic perovskite/silicon tandem solar cells on commercially textured silicon with conformal perovskite top cells allow compatibility with standard industrial processes of silicon photovoltaic, as well as maximization of light trapping at the least cost. However, the efficiency is still limited by unsatisfactory open‐circuit voltage (VOC) and fill factor (FF), owing to the challenge of growing high‐quality perovskite film on textured substrates and the lack of particularly effective passivation at the inferior interface between perovskite and C60. Different from traditionally electricity‐insulating passivator, herein, a conductive organic amine salt is introduced into this interface to suppress nonradiative recombination loss and promote carriers transfer synchronously, significantly increasing the VOC while preserving high FF, thus improving the efficiency substantially. Finally, a champion efficiency of up to 28.51% is obtained. Furthermore, due to the favorable electrical properties of this molecule, there is a wide processing window for the passivation, which helps to achieve an efficiency of 25.13% when the active area is enlarged to 11.879 cm2.

Quaternary Ammonium-Tethered Phenylboronic Acids Appended Supramolecular Nanomicelles as a Promising Bacteria Targeting Carrier for Nitric Oxide Delivery.

The delivery of drugs to focal sites is a central goal and a key challenge in the development of nanomedicine carriers. This strategy can improve the selectivity and bioavailability of the drug while reducing its toxicity. To ensure the specific release of nitric oxide at the site of a bacterial infection without damaging the surrounding normal tissue, we designed a host-guest molecule containing a host molecule with a target moiety and a nitric oxide donor to release nitric oxide. The boronic acid group in the structure of this nanoparticle interacts strongly and specifically with the surface of E. coli. In addition, the quaternary amine salt can interact electrostatically with bacteria, indicating a large number of negatively charged cell membranes; altering the molecular structure of the cell membrane; increasing the permeability of the cell membrane; and causing cytoplasmic diffusion and cell lysis, resulting in lethal activity against most bacteria. The synthesised molecules were characterised by 1H NMR and mass spectrometry. The strong specific interaction of the boronic acid moiety with the surface of E. coli and the electrostatic interaction of the quaternary amine salt with the cell membrane were confirmed by antibacterial experiments on molecules with and without the targeting moiety. The targeting group-modified micelles enhanced the antibacterial effect of the micelles very effectively through specific interactions and electrostatic interactions. In addition, in vitro skin wound healing experiments also confirmed the targeting and antimicrobial effect of micelles. These results suggest that the specific release of nitric oxide at the site of bacterial infection is an important guide to further address the emergence of antibiotic-resistant strains of bacteria.

Polymerizable Ammonium Salt Interlayer for Efficient and Stable NiOx-Based Perovskite Solar Cells

Although the research of formal perovskite solar cells (PSCs) has achieved great breakthroughs, the use of doped small-molecule organic hole transport layers limits the improvement of stability. PSCs with an inverted form show great potential in a more stable device structure. In this paper, a NiOx/3D perovskite interface in inverted PSCs was modified with a polymerizable amine salt (2-methylallylamine hydroiodide (CTBAI)) interlayer. The double bonds contained in CTBAI thermally induced polymerization of a thin film after heat treatment, resulting in the formation of amine salts with longer molecular chains. The modified layer can improve crystallinity and reduce defects in the film, as well as optimize the interface energy level and reduce interface recombination. The efficiency of NiOx-based inverted PSCs based on the optimized interface increased from 17.0% to 18.2%. After 280 h of MPP testing, the encapsulated device tested in ambient air (RH = 50–60%) demonstrated a robust light stabilization and maintained over 93% efficiency.

N-Alkyl Carbamoylimidazoles as Isocyanate Equivalents: Exploration of the Reaction Scope for the Synthesis of Ureas, Hydantoins, Carbamates, Thiocarbamates, and Oxazolidinones.

The reaction of the HCl or trifluoroacetic acid salts of primary amines with carbonyldiimidazole (CDI) is shown to be a preparatively useful method for forming monosubstituted carbamoylimidazoles (28 examples) without the formation of symmetrical urea side products. The utility of these air- and water-stable crystalline carbamoylimidazole reagents was demonstrated by their reactions as blocked or masked isocyanate equivalents. Reaction with various classes of nucleophiles provides access to useful functional groups including ureas, carbamates, thiocarbamates, hydantoins, and oxazolidinones. A parallel synthesis library of 30 ureas was generated by the reaction of 6× carbamoylimidazole intermediates with 5× amines and triethylamine. The unsymmetrical urea-containing natural products macaurea A and pygmaniline A were also prepared in good yields (95% over four steps and 79% over three steps, respectively) using this approach. The reaction of carbamoylimidazoles with amino acid methyl esters followed by microwave irradiation in aqueous media gives hydantoins in high yields, further demonstrating the ability of carbamoylimidazoles as isocyanate surrogates. Three hydantoin-containing natural products including macahydantoin D and meyeniihydantoin A were prepared in nearly quantitative yields from proline methyl ester and carbamoylimidazoles. The reaction of carbamoylimidazoles with alcohols and thiols under basic conditions affords carbamates and thiocarbamates, respectively, in good yields. Lastly, a method for the preparation of chiral oxazolidinone heterocycles from chiral epoxy alcohols is demonstrated using a double displacement approach. The reactions occur with high regio- and stereoselectivity (dr ≥ 15:1 by 1H NMR) via a domino attack of the corresponding alkoxides with carbamoylimidazoles followed by an intramolecular attack of the in situ generated urea anion at the proximal position of the epoxide group.

Short Tryptamine-Based Peptoids as Potential Therapeutics for Microbial Keratitis: Structure-Function Correlation Studies.

Peptoids are peptidomimetics that have attracted considerable interest as a promising class of antimicrobials against multi-drug-resistant bacteria due to their resistance to proteolysis, bioavailability, and thermal stability compared to their corresponding peptides. Staphylococcus aureus is a significant contributor to infections worldwide and is a major pathogen in ocular infections (keratitis). S. aureus infections can be challenging to control and treat due to the development of multiple antibiotic resistance. This work describes short cationic peptoids with activity against S. aureus strains from keratitis. The peptoids were synthesized via acid amine-coupling between naphthyl-indole amine or naphthyl-phenyl amine with different amino acids to produce primary amines (series I), mono-guanidines (series II), tertiary amine salts (series III), quaternary ammonium salts (series IV), and di-guanidine (series V) peptoids. The antimicrobial activity of the peptoids was compared with ciprofloxacin, an antibiotic that is commonly used to treat keratitis. All new compounds were active against Staphylococcus aureus S.aureus 38. The most active compounds against S.aur38 were 20a and 22 with MIC = 3.9 μg mL−1 and 5.5 μg mL−1, respectively. The potency of these two active molecules was investigated against 12 S. aureus strains that were isolated from microbial keratitis. Compounds 20a and 22 were active against 12 strains with MIC = 3.2 μg mL−1 and 2.1 μg mL−1, respectively. There were two strains that were resistant to ciprofloxacin (Sa.111 and Sa.112) with MIC = 128 μg mL−1 and 256 μg mL−1, respectively. Compounds 12c and 13c were the most active against E. coli, with MIC > 12 μg mL−1. Cytoplasmic membrane permeability studies suggested that depolarization and disruption of the bacterial cell membrane could be a possible mechanism for antibacterial activity and the hemolysis studies toward horse red blood cells showed that the potent compounds are non-toxic at up to 50 μg mL−1.

Amine Salts Vapor Healing Perfected Perovskite Layers for NiOx Based p‐i‐n Solar Cells

AbstractPost‐treatment is a widely used strategy to reduce defects in perovskite films, but has been largely limited to the solution phase. Herein, the posttreatment tool kit and develop a universal amine salts (AIXI) vapor healing strategy by taking advantage of the penetrating power of vapor and the soft‐matter characteristics of halide perovskite is expanded. In a striking demonstration, the post‐treatment of pristine perovskite layers allows simultaneous filling of the MA+ and I– vacancies, passivation of both the cation and anion defects, and healing of the films to high order and high crystallinity required for high device performance, from the surface to the bulk and all the way down to the bottom. Experiments and DFT calculations revealed that charge extraction can be enhanced and non‐radiative recombination can be reduced by regulating the energy levels and reducing the trap states via the AIXI vapor healing. Moreover, the diffusing AIXI can reach the NiOx surface to obstruct the undesirable interfacial reactions and passivate the interface defects, further reducing the open‐circuit voltage (Voc) loss. The vapor healing strategy substantially reduces the trap density from 4.76 × 1015 to 1.04 × 1015 cm–3, and promots power conversion efficiency of the champion device from 17.92% to 20.48% with superior device consistency, Voc up to 1.114 V and the operational device stability.

Single‐step post‐production treatment of lead acetate precursor‐based perovskite using alkylamine salts for reduced grain‐boundary related film defects

AbstractPowered by the worldwide efforts of research groups experienced in dye‐sensitized, and thin‐film solar cells, perovskite solar cells (PSCs) reached a power conversion efficiency of 25.7% within 10 years. However, the presence of defects and trap density within the active layer's grain boundaries commonly operates as non‐radiative recombination centers. Hence, intensive efforts have been reported to passivate the inevitable bulk and interface defects of the active layer using additives or post‐treatment processing to enhance the efficiency and stability of PSCs. Herein, a facile post‐treatment strategy based on wet processing methylammonium lead triiodide, MAPbI3 (prepared from lead acetate and methylammonium iodide precursors) films with organic amine salts (FABr and FAI) is demonstrated. As a result, high‐quality films of mixed perovskites (FAxMA1‐xPbI3‐xBrx and FAxMA1‐xPbI3) were obtained. The surface treatment has efficiently passivate the defects in the host film, suppressing the non‐radiative carrier recombination. Compared to the control device, the increased open‐circuit voltage (from 0.5 V to 1 V) and fill factor (FF) values of the optimized device based on FAxMA1‐xPbI3 showed a PCE of 16.13%. And our findings revealed that post‐treatment is possible on wet perovskite film aged for a few minutes prior to its post‐treatment, which saved the energy used for pre‐annealing.

PH-responsive water-in-oil emulsions with reversible phase inversion behavior stabilized by a novel dynamic covalent surfactant

The dynamic covalent nature of imine bonds provides a facile avenue to develop stimuli-responsive emulsifiers and has attracted considerable interest. In petroleum engineering, the development of smart emulsifiers that can be switched on demand to achieve the reversible phase inversion of the invert emulsion drilling fluid (IEDF) can effectively aid in its removal during cleanup. To this end, a novel dynamic covalent surfactant (TA-CBA) that can precisely manipulate the emulsion type by responding to acid/base stimuli was synthesized through the Schiff base reaction between 1-tetradecylamine (TA) and 4-carboxybenzaldehyde (CBA). Evaluation of the surface tension and interfacial tension (IFT) showed that the imine-bonded product TA-CBA was a surfactant with strong IFT reduction ability. At pH 7.4, the prepared water-in-oil (W/O) emulsions were stable without any separated phases after storage for 48 h and even after high-temperature aging at 210 °C. As the pH decreased from 7.4 to 4, the emulsion inverted from a higher viscosity W/O emulsion to a lower viscosity oil-in-water (O/W) emulsion. Remarkably, after the pH was adjusted back to 7.4, the rheological parameters and stability of the emulsion could be triggered at the original W/O emulsion level. 1H NMR and IFT measurements revealed that the reversible formation and breakage of covalent imine bonds led to the production of CBA and cationic amine salt (TA+), establishing the pH reversibility of the emulsion type and its rheological properties. Finally, we successfully formulated a reversible IEDF using TA-CBA as the sole emulsifier, which not only has reasonable rheological properties, filtration performance, and emulsification stability but also allows for easy cleanup. The IEDF can be phase-inverted into a water-soluble O/W emulsion drilling fluid at pH 4 and achieved a removal efficiency of 98.13 %.