Synthesis, Surface-Active Properties, and Antimicrobial Activities of New Neutral and Cationic Trimeric Surfactants

Designing the structure of cationic star-shaped trimeric surfactants most active in micelle formation using molecular connectivity indices

A model expressing the relationship between the logarithm of critical micelle concentration of cationic star-shaped trimeric surfactants and topological indices was obtained using only molecular connectivity indices. Based on the obtained model, the exemplary compound most active in micelle formation was designed. The analysis of the influence of various structural factors on the value of the critical micelle concentration was supported by atomic charge studies. The obtained model will be used to design new star-shaped trimeric surfactants that are more active in formation of micelle as well as to predict their critical micelle concentration.

Structural Analysis of Aggregates Formed by Linear- and Star-type Quaternary Ammonium Salt-Based Trimeric Surfactants Using Rheology and Small-Angle X-ray Scattering

We performed a structural analysis of aggregates formed by two types of trimeric surfactants based on quaternary ammonium salts─linear-type 3Cnlin-s-Q and star-type 3Cntris-s-Q─featuring varying alkyl chain lengths (n) and spacer chain lengths (s) in aqueous solutions. We performed rheology, dynamic light scattering, and small-angle X-ray scattering measurements on the trimeric surfactants and investigated the effects of the alkyl chain length, spacer chain length, spacer skeleton structure, and surfactant concentration on their aggregation behavior. Linear-type 3C12lin-3-Q transitioned from gel solutions to worm-like micelles at high concentrations, and 3C14lin-3-Q became gel solutions over a wide range of concentrations. In contrast, all other studied surfactants formed ellipsoidal micelles. The minor and major axes of the ellipsoidal micelles formed by liner-type 3Cnlin-3-Q increased with the increasing alkyl chain length. As the spacer chain length of 3Cnlin-s-Q increased from 3 to 6, and as the spacer skeleton expanded from linear-type 3Cnlin-s-Q to star-type 3Cntris-s-Q, the surfactants formed ellipsoidal micelles without the formation of aggregates with a high-order structure, demonstrating this behavior over a broad concentration range.

Preparation and Performance Evaluation of Gemini Sulphobetaine Surfactant Bis{[(N-methyl-N-(3-alkoxy-2-hydroxy) propyl-N-(3-sulfonic) propyl] methylene}

Surfactants are very often used in tertiary oil production. However, the conventional surfactants cannot be used in high salinity reservoirs of tertiary oil production because the high salinity leads to the deactivation of the surfactants. Gemini sulpho-betaine surfactants have been developed to meet the requirements of tertiary oil production in such reservoirs. In this study, the Gemini sulphobetaine surfactant (bis{[(N-methyl-N-(3-alkoxy-2-hydroxy)propyl-N-(3-sulfonate)propyl]methylene}) was prepared by etherification, ring opening reaction and sulfonation reaction with decyl alcohol, epichlorohydrin, N,N’-dimethyl ethylene diamine and 1,3-propanesultone. The experimental conditions obtained are: the ratio of 1,3-propanesulfonic acid lactone to tertiary amine intermediate = 2.3 : 1, reaction temperature = 70°C and reaction time = 11 h. The analysis of the infrared spectrum showed that the structure of the synthesised substance corresponds to that of a Gemini sulphobetaine surfactant. The chemical shifts of the groups were determined by 1HNMR structural characterisation of the products. The surface tension, emulsifying properties, foaming properties and wetting properties were investigated. The results showed that the surfactant has good foaming properties and good compatibility in a high salt environment.

Sodium N-lauryl amino acids derived from silk protein can form catanionic aggregates with cytarabine as novel anti-tumor drug delivery systems

A sodium N-lauryl amino acids (shortly silk sericin surfactant, SSS) is synthesized with lauryl chloride and sericin amino acids recovered from silk industrial waste. The purpose of this study is to explore whether the sericin surfactant can be used as a potential drug delivery carrier. By controlling the proportion of cationic drugs, cytarabine hydrochloride (CH) and anionic SSS, the aggregation behavior, slow release capability and toxicological effects of catanionic aggregates or vesicles, formed through CH and SSS, have been investigated in detail. Dynamic light scattering (DLS), transmission electron microscopy (TEM), and zeta potential analysis showed that the aggregate solution could form a stable vesicle structure when the mass fraction of CH is less than or equal to 0.3. The drug release results showed that the cumulative release rate of the catanionic aggregation solution with CH mass fraction of 0.2 reached a maximum at 18 h, being approximately 9 times greater than that of pure cytarabine. The CH/SSS aggregates had a significant sustained release effect compared with the control group. At the same time, vesicles formed by SSS and CH have better anti-tumor effects compared with the pure drug group. In summary, sericin surfactant from silk industrial waste has a potential use as a drug delivery carrier.

Validating interfacial behaviour of surface-active ionic liquids (SAILs) with computational study integrated with biocidal and cytotoxic assessment

Surface-active ionic liquids (SAILs) belonging to the series of N-alkylmethylimidazolium halides [C₈mimX] (X = Br, Cl, and BF₄) and [C_nmimBr] (n = 10, 12, 14, and 16) were employed to understand the influence of hydrophobicity of alkyl chain length and the chaotropicity of counter-ions of SAILs on the micellization, antimicrobial action and cytotoxicity properties. The micellization phenomenon of SAILs in an aqueous environment was examined employing tensiometry and steady-state fluorescence spectrophotometry. The corresponding interfacial parameters viz., critical micelle concentration (CMC), effectiveness (γ_CMC), surface pressure (П_CMC), maximum surface excess concentration (Г_max), and the minimum area engaged per molecule (A_min) at the air-water interface were evaluated at 303.15 K. These experimental findings were monitored and geometrically optimized theoretically using Gaussian software to highlight the recent advances in this field of theoretical calculations for putative structure. The simulation descriptors correlated the micellization behavior as a function of hydrophobicity which may contribute to obtaining awareness on their ecological behavior and fate. In addition, the biological screening of all the examined SAILs was undertaken with a combined experimental and theoretical (optimized) method against bacteria and fungus. Results revealed that SAILs with the alkyl chain-length greater than C₈- act as a fair antimicrobial agent against the selected microbial strain which is attributed to the enhanced degree of SAILs hydrophobicity. The cytotoxicity of these imidazolium-based SAILs was also assessed on the cervical human cell line (HeLa) using the MTT cell viability assay and the data thus obtained were subjected to statistical analysis.

Self-Assembly and Functions of Star-Shaped Oligomeric Surfactants

Oligomeric surfactants consist of three or more amphiphilic moieties which are connected by spacer groups covalently at the level of headgroups. It provides a possible route to bridge the gap from conventional single-chain surfactants to polymeric surfactants and leads to many profound improvements in the properties of surfactants in aqueous solution and at the air/water and water/solid interfaces. Generally, oligomeric surfactants are categorized into linear, ring-like, and star-shaped on the basis of the topological structures of their spacer groups, and their aggregation behavior strongly depends on the resultant topological structures. In recent years, we studied trimeric, tetrameric, and hexameric surfactants with a star-shaped spacer which spreads from a central site of elemental nitrogen or carbon, and their charged headgroups connect with each other through the spacers. It has been found that both the nature of spacer groups and the degree of oligomerization show important influences on the self-assembly of oligomeric surfactants and provide great possibilities in fabricating various surfactant aggregate morphologies by adjusting the molecule conformations. The unique self-assembly behavior endows them with superior physicochemical properties and potential applications. This feature article summarizes the development of star-shaped oligomeric surfactants, including self-assembly at the air/water and water/solid interfaces, self-assembly in aqueous solution, and their functions. We expect that this review could provide a comprehensive understanding of the structure-property relationship and various potential applications of star-shaped oligomeric surfactants and offer additional motivation for their future research.

Design of polyurethane acrylic antimicrobial films via one-step UV curing

A series of films with excellent antimicrobial properties is prepared from QACs bearing hydrophobic tails and a polyurethane acrylate prepolymer via one-step UV curing.

Building a Better Quaternary Ammonium Compound (QAC): Branched Tetracationic Antiseptic Amphiphiles

Bacteria contaminate surfaces in a wide variety of environments, causing severe problems across a number of industries. In a continuation of our campaign to develop novel antibacterial quaternary ammonium compounds (QACs) as useful antiseptics, we have identified a starting material bearing four tertiary amines, enabling the rapid synthesis of several tris- and tetracationic QACs. Herein we report the synthesis and biological activity of a series of 24 multiQACs deemed the "superT" family, and an investigation of the role of cationic charge in antimicrobial and anti-biofilm activity, as well as toxicity. This class represents the most potent series of QACs reported to date against methicillin-resistant Staphylococcus aureus (MRSA), with minimum inhibitory concentrations (MICs) and minimum biofilm eradication concentrations (MBECs) as low as 0.25 and 25 μm, respectively. Based on the significant cell-surface-charge differences between bacterial and eukaryotic cells, in certain cases we observed excellent efficacy-to-toxicity profiles, exceeding a 100-fold differential. This work further elucidates the chemical underpinnings of disinfectant efficacy versus toxicity based on cationic charge.

Synthesis and Surface Active Properties of Novel Oligomer Betaine Surfactants

A new type of oligomer betaine surfactants pentasodium N,N′,N″-alkyl diethylene triamine pentaacetic acid containing five carboxylate groups, three quaternary ammonium groups and three hydrophobic groups was synthesized by alkaline neutralization reaction and quaternization with diethylene triamine pentaacetic acid, sodium hydroxide and long chain alkyl bromide as main raw materials. The chemical structures of the prepared compounds were confirmed by FTIR, 1H NMR, MS spectroscopy and elementary analysis. With the increasing length of the carbon chain, the CMC of the synthesized compounds initially decreased. The surface active properties of these compounds were superior to that of the single chain betaine surfactants rich as decyl dimethyl betaine. The efficiency of adsorption at the water/air interface (pC20) of these surfactants was very high. It is found that the shorter hydrocarbon chain length of oligomer betaine surfactants, the faster the rate of reduction of surface tension, and the bigger the aggregation number of oligomer betaine surfactants are. Their foaming properties and wetting ability toward a felt chip, and lime-soap dispersing ability were investigated.

Synthesis and properties of multiheaded and multitailed surfactants based on tripentaerythritol

The surface and self-assembly properties of a family of multiheaded, multitailed surfactants based on a tripentaerythritol backbone are described. Critical aggregation concentrations of these unusual surfactant systems have been determined from surface tension measurements; aggregate sizes in the presence and absence of a small amount of added electrolyte have been obtained via dynamic light scattering, and the morphologies of the aggregates were examined from electron microscopy measurements. In general, when compared to conventional ionic and two-headed surfactants (and other recently synthesized pentaerythritol derived surfactants from this group), these multiheaded surfactants exhibited some unusual trends in their aggregation behaviour and interesting aggregate structures in aqueous solution, as a function of alkyl chain length.

Novel Cationic Gemini Surfactants and Methods for Determination of Their Antimicrobial Activity – Review

Newly series of Gemini surfactants have emerged which are composed of two hydrophobic tails and two cationic head groups linked by spacer group. Today, these cationic Gemini surfactants are attracting attention of the researchers as these surfactants are more efficient in lowering surface tension as the conventional ones. Cationic Gemini surfactants have lower critical micelle concentrations (CMC) and higher surface tension reduction as compared to those of corresponding monoalkyl ammonium salts. They have wide industrial and household applications. They can be used as emulsifiers, dispersing and anti-foaming agents etc. Cationic Gemini surfactants show good antimicrobial activity against gram-positive and gram-negative bacteria. Antimicrobial activity has also been studied against fungi and yeast species. These cationic Gemini surfactants can be used as antibacterial, antifungal, antiviral agents. This review paper deals with synthesis, antimicrobial activity, methods for determining antimicrobial activity (MIC means minimum inhibitory concentration) and applications of cationic Gemini surfactants.

Synthesis and Surface Active Properties of Dimeric Gemini Sulfonate Surfactants

Dimeric Gemini sulfonate surfactants 1,2-di-(2-oxoypropyl sulfonate-3-alkylether- propoxy) ethane were prepared by the reaction of ethylene glycol diglycidyl ether with long-chain alcohols, followed by sulfonation with 1,3-propane sultone. Ethylene glycol ether was synthesized by the reaction of epichlorohydrin with ethylene glycol. The chemical structures of the prepared compounds were confirmed by FTIR, 1H NMR and elementary analysis. With the increasing length of the carbon chain, the values of their CMC initially decreased. The longer alkyl chain is, the higher melting point is. The Krafft point of Gemini sulfonate surfactants was below 0°C and they had good water solubility. These compounds were superior in surface active properties to general sulfonate surfactants SDS. The efficiency of adsorption at the water/air interface (pC20) of these surfactants was very high. Their foaming properties and wetting ability toward a felt chip, and lime-soap dispersing ability were investigated.

Surfactants Possessing Multiple Polar Heads. A Perspective on their Unique Aggregation Behavior and Applications

Surfactants containing more than one head group are known to exhibit a wide range of interesting properties as they undergo aggregation in water. The correlation between the molecular structure of these surfactants and their properties (for example, critical micellar concentration, aggregation number, morphology, counterion dissociation, fractional charge, etc.) can provide useful information to define the structure-activity relationship. The influence of the number of head groups on the surfactant aggregation is further evident from interesting interfacial behavior, seen in biological applications. This Perspective highlights recent trends in surfactant aggregation effects and focuses on emerging challenges in the field.

Aggregation behavior of gemini surfactants and their interaction with macromolecules in aqueous solution

Gemini surfactants are constructed by two hydrophobic chains and two polar/ionic head groups covalently connected by a spacer group at the level of the head groups. Gemini surfactants possess unique structural variations and display special aggregate transitions. Their aggregation ability and aggregate structures can be more effectively adjusted through changing their molecular structures compared with the corresponding monomeric surfactants. Moreover, gemini surfactants exhibit special and useful properties while interacting with polymers and biomacromolecules. Their strong self-aggregation ability can be applied to effectively influence the aggregation behavior of both polymers and biomacromolecules. This short review is focused on the performances of gemini surfactants in aqueous solutions investigated in the last few years, and summarizes the effects of molecular structures on aggregation behavior of gemini surfactants in aqueous solution as well as the interaction of gemini surfactants with polymers and biomacromolecules respectively.

Molecular conformation-controlled vesicle/micelle transition of cationic trimeric surfactants in aqueous solution

Two star-like trimeric cationic surfactants with amide groups in spacers, tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD) and tri(dodecyldimethylammonioacetoxy)tris(2-aminoethyl)amine trichloride (DDAD), have been synthesized, and the aggregation behavior of the surfactants in aqueous solution has been investigated by surface tension, electrical conductivity, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, and NMR techniques. Typically, both the surfactants form vesicles just above critical aggregation concentration (CAC), and then the vesicles transfer to micelles gradually with an increase of the surfactant concentration. It is approved that the conformation of the surfactant molecules changes in this transition process. Just above the CAC, the hydrophobic chains of the surfactant molecules pack more loosely because of the rigid spacer and intramolecular electrostatic repulsion in the three-charged headgroup. With the increase of the surfactant concentration, hydrophobic interaction becomes strong enough to pack the hydrophobic tails tightly and turn the molecular conformation into a pyramid-like shape, thus leading to the vesicle to micelle transition.