Synthesis and interfacial properties of ethoxylated cationic surfactants derived from n-dodecyl glycidyl ether

Manipulating the hydrophilic / hydrophobic balance in novel cationic surfactants by ethoxylation: The impact on adsorption and self-assembly

HYPOTHESIS

Cationic surfactants have a wide range of applications, often associated with their affinity for a range of solid surfaces and their anti-microbial properties. Manipulating their adsorption and self-assembly properties is key to most applications, and this is commonly achieved through surfactant mixtures or manipulating their headgroup or alkyl chain structure. Achieving this through adjustments to their headgroup structure is less common in cationic surfactants than in anionic surfactants. Ethoxylation provides the ability to adjust the hydrophilic / hydrophobic balance, as extensively demonstrated in a range of anionic surfactants.

EXPERIMENTS

This same approach has been applied here to a range of ethoxylated cationic surfactants in the form of the quaternary ammonium salts, and their tertiary nonionic equivalents before quaternisation. Their adsorption and self-assembly properties are investigated using predominantly the neutron scattering techniques of neutron reflectivity, NR, and small angle neutron scattering, SANS.

FINDINGS

The trends in the adsorption at the air-water interface and the self-assembly in aqueous solution demonstrate how the hydrophilic / hydrophobic balance can be adjusted by varying the degree of ethoxylation and the alkyl chain length, and illustrate the degree of interdependence of the different structural changes. The variation in the adsorption and the micelle structure shows how the surfactant conformation / packing changes as the degree of ethoxylation and alkyl chain length increases and how the introduction of charge induces further changes.

Onosma mutabilis: Phytochemical composition, antioxidant, cytotoxicity, and acute oral toxicity

The traditional use of Onosma L. species as a remedy motivated scientists to discover great biological/pharmacological potentials in this plant. In the current study, in addition to the phytochemical composition of methanol (MeOH), water, and ethyl acetate extract of aerial parts of Onosma mutabilis Boiss., an endemic plant species in the flora of Kurdistan, Iraq, in vitro antioxidant, cytotoxicity, and oral toxicity activity were investigated. Results of total phenolic and total flavonoid tests show the MeOH extract superiority, and the results of Gas chromatography-mass spectrophotometer(GS/GS-MS) show 18 chemical compounds in the MeOH extract, and the majority of the detected compounds were alkaloids (78.77%) and steroids (11.48%), namely as 5,8-dihydroxy-2-(4-methylpent-3-enyl) naphthalene-1,4-dione (48.60%), 3-O-Methyl-d-glucose (27.49%), β-Sitosterol (6.81%), Phenol, 2,4-bis (1,1-dimethyl ethyl)-, phosphite (3.46%), and 24,25-Dihydroxycholecalciferol (3.14%). Results of the antioxidant tests show the MeOH extract superiority in the phosphomolybdenum assay, radical scavenging [on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)] assays, and reducing power [cupric reducing antioxidant capacity (CUPRAC) and ferric reducing antioxidant power (FRAP)] assays (1.45, 3.54, 2.33, 1.12, 1.62, mg/ml, respectively). The cytotoxicity results of the plant extract are presented as IC50 (inhibitory concentration at 50%) on the prostate cancer cells (DU-145), mammary cancer cells (MCF-7), and human cervix carcinoma (Hep2c), at which values ranged from 28.79 to 41.83 μg/ml. Results of the acute toxicity in the dose-dependent trail (100, 200, 300, 600 mg/kg of MeOH) show the absence of the behavior and appearance changes of female Wister rats. Overall, O. mutabilis extract exhibited significant natural potentials probably because of its polar phytochemicals, which could be an alternative source for remedial, nutrient, and cosmetic manufacture.

Synthesis and Evaluation of Zwitterionic Surfactants Bearing Benzene Ring in the Hydrophobic Tail

Surfactant tolerance in the presence of mono and divalent reservoir ions, as well as the solubility of surfactant in high salinity and low salinity brine, are the two major requirements for any surfactant that is subjected to oilfield application. Herein, six poly(ethylene oxide) zwitterionic surfactants having different ionic headgroups and hydrophobic tail were synthesized for oilfield applications. They were characterized by various instrumental techniques (Fourier-transform infrared spectroscopy (FTIR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS), Nuclear Magnetic Resonance (NMR)) and the combination of these techniques allowed for us to deduce the structure. All of the surfactants revealed prominent solubility in high salinity and low salinity brine due to the presence of ethoxy units between the aromatic ring and amide group. The surfactant samples were oven aged for 90 days at reservoir temperature and a clear solution implies their excellent aqueous stability. Rendering to thermal gravimetric results, decomposition of surfactants was found to occur around 300 °C, which is higher than the reservoir temperature (≥90 °C). It was observed that the hydrophilic headgroup has no significant impact on the critical micelle concentration and other surface properties. However, the hydrophobic tail bearing benzene ring significantly alters the critical micelle concentration and other surface properties.

Synthesis of Novel Ethoxylated Quaternary Ammonium Gemini Surfactants for Enhanced Oil Recovery Application

Two aspects are always considered in the design and development of new surfactants for oilfield application. One of them is that surfactant must be sufficiently stable at reservoir temperature and the other is the solubility of the surfactant in the injection water (usually seawater) and the formation brine. Most industrially applied surfactants undergo hydrolysis at elevated temperature and the presence of reservoir ions causes surfactant precipitation. In relevance to this, a novel series of quaternary ammonium gemini surfactants with different length of spacer group (C8, C10, and C12) was synthesized and characterized using FT-IR, 13C NMR, 1H NMR, and MALDI-TOF MS. The gemini surfactants were prepared by solvent-free amidation of glycolic acid ethoxylate lauryl ether with 3-(dimethylamino)-1-propylamine followed by reaction with dibromoalkane to obtain quaternary ammonium gemini surfactants. The gemini surfactants were examined by means of surface properties and thermal stabilities. The synthesized gemini surfactants showed excellent solubility in the formation brine, seawater, and deionized water without any precipitation for up to three months at 90 °C. Thermal gravimetric data revealed that all the gemini surfactants were decomposed above 227 °C, which is higher than the oilfield temperature (≥90 °C). The decrease in critical micelle concentration (CMC) and surface tension at CMC (γcmc) was detected by enhancing spacer length in the order C8 ˃ C10 ˃ C12 which suggested that the larger the spacer, the better the surface properties. Moreover, a further decrease in CMC and γcmc was noticed by enhancing temperature (30 °C ˃ 60 °C) and salinity (deionized water ˃ seawater). The current study provides a comprehensive investigation of quaternary ammonium gemini surfactants that can be further extended potentially to use as a suitable material for oilfield application.