This work reports that cationic micelles formed by cationic trimeric, tetrameric, and hexameric surfactants bearing amide moieties in spacers can efficiently kill Gram-negative E. coli with a very low minimum inhibitory concentration (1.70-0.93 μM), and do not cause obvious toxicity to mammalian cells at the concentrations used. With the increase of the oligomerization degree, the antibacterial activity of the oligomeric surfactants increases, i.e., hexameric surfactant > tetrameric surfactant > trimeric surfactant. Isothermal titration microcalorimetry, scanning electron microscopy, and zeta potential results reveal that the cationic micelles interact with the cell membrane of E. coli through two processes. First, the integrity of outer membrane of E. coli is disrupted by the electrostatic interaction of the cationic ammonium groups of the surfactants with anionic groups of E. coli, resulting in loss of the barrier function of the outer membrane. The inner membrane then is disintegrated by the hydrophobic interaction of the surfactant hydrocarbon chains with the hydrophobic domains of the inner membrane, leading to the cytoplast leakage. The formation of micelles of these cationic oligomeric surfactants at very low concentration enables more efficient interaction with bacterial cell membrane, which endows the oligomeric surfactants with high antibacterial activity.

Vast wastage of pesticides has caused significant environmental pollution and economic loss, which occurs in any step during the entire process of pesticide application. However, the existing strategies for controlling pesticide losses are step specific. Here, a comprehensive strategy to substantively improve pesticide efficiency on the basis of precise designs from beginning to end is developed. A water‐based coacervate with synthesized imine‐based dynamic covalent trimeric surfactants to synergistically control encapsulation, deposition, retention, and release of pesticides on water‐repellent plants is constructed. The coacervate consists of nanosized networks and abundant tightly bonded water, leading to effective encapsulation of hydrophilic/hydrophobic pesticides. Meanwhile, the network‐like microstructure entangles with the micro/nanostructures of superhydrophobic surface, ensuring complete deposition on superhydrophobic plant surface after high‐speed impact and inhibition of wind/rainwater erosion. Moreover, the CO2‐induced degradative surfactant coacervate determines the precise pesticide release. The dynamic coacervate as an innovative pesticide formula provides a prospective way for pesticide application, and is expected to promote productive and sustainable agriculture.

A star-shaped hexameric quaternary ammonium surfactant (PAHB), bearing six hydrophobic chains and six charged hydrophilic headgroups connected by an amide-type spacer group, was synthesized. The self-assembly behavior of the surfactant in aqueous solution was studied by surface tension, electrical conductivity, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, and NMR techniques. The results reveal that there are two critical aggregate concentrations during the process of aggregation, namely C(1) and C(2). The aggregate transitions are proved to be caused by the changes of the surfactant configuration through hydrophobic interaction among the hydrocarbon chains. Below C(1), PAHB may present a star-shaped molecular configuration due to intramolecular electrostatic repulsion among the charged headgroups, and large aggregates with network-like structure are observed. Between C(1) and C(2), the hydrophobic interaction among the hydrophobic chains may become stronger to make the hydrophobic chains of the PAHB molecules curve back and pack more closely, and then the network-like aggregates transfer to large spherical aggregates of ∼100 nm. Beyond C(2), the hydrophobic interaction may become strong enough to cause the PAHB molecular configuration to turn into a pyramid-like shape, resulting in the transition of the spherical large aggregates to spherical micelles of ∼10 nm. Interestingly, the PAHB displays high emulsification ability to linear fatty alkyls even at very low concentration.

self-cleaning and antifouling ability for repelling the deposition of other materials and liquid confining properties for enhancing printing resolution and avoiding coffee-ring effects. [13] However, inertial water drops impacting superhydrophobic surfaces can bounce off quickly or splash violently. [14][15][16][17][18][19][20][21][22][23] Undesired rebound and splash cause material waste [24] and weaken the related performance and efficiency. Many attempts have been conducted to promote water drop spreading on hydrophobic surfaces by using polymers [1,23,[25][26][27][28] or surfactants. [22,[29][30][31][32] However, these two methods still have drawbacks for achieving drop deposition, not to mention uniform spreading: 1) Polymer additives can delay drop retraction but leave drops with hemispherical shape and nonuniform material distribution on the hydrophobic substrate.2) The poor wettability and large mole cular weight of polymer additives restrict the ejecting process during inkjet printing. 3) Surfactant additives can promote drop spreading in a static state owing to the reduced surface tension (γ); [33] however, the low surface tension increases the instability of the impacting drop and leads to drop splashing with satellite droplets, according to the Kelvin-Helmholtz instability, [34] k max ∼ 2ρ a U r 2 /3γ (ρ a is the air density). It is therefore a great challenge for uniform shape spreading on superhydrophobic surfaces without any loss of the drops. Here, we show a new and simple strategy for uniform round-shape drop spreading on superhydrophobic surfaces after high-speed impact, up to 5.0 m s −1 , by utilizing live-oligomeric surfactant jamming, diethylenetriamine/sodium dodecyl sulfate (triamine/SDS). The live-oligomeric surfactant, which noncovalently constructed by SDS and triamine through electrostatic interaction, has a dynamic equilibrium between monomer surfactant and oligomeric surfactant. Figure 1 shows the contrast spread dynamics of a liveoligomeric surfactant drop and other drops impacting superhydrophobic surfaces at an impacting velocity (U ) of 2.42 m s −1 from side and bottom views (Movie S1, Supporting Information). The diameter (D 0 ) of pure water and the surfactant drops is ≈2.25 and 1.90-2.00 mm, respectively (Figure S1, Supporting Information for experimental setup). The Weber number (We), We = ρDV 2 /γ, of water, SDS, N2C3/SDS, triamine/SDS, and 12-3-12-3-12 is 182. 68, 295.29, 358.29, 383.00, and 292.29, respectively. The superhydrophobic surface [35] composed of random micro-nanostructures of typical size and spacing of Inkjet printing of water-based inks on superhydrophobic surfaces is important in high-resolution bioarray detection, chemical analysis, and highperformance electronic circuits and devices. Obtaining uniform spreading of a drop on a superhydrophobic surface is still a challenge. Uniform round drop spreading and high-resolution inkjet printing patterns are demonstrated on superhydrophobic surfaces without splash or rebound after high-speed impacting by introducing...

Effects of a "gemini-type" organic salt 1,2-bis(2-benzylammoniumethoxy) ethane dichloride (BEO) on the aggregation behavior of sodium dodecylsulfate (SDS) have been investigated by turbidity, surface tension, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, 1 H NMR spectroscopy, and differential scanning microcalorimetry. The aggregation behavior of the SDS/BEO mixed aqueous solution shows strong concentration and ratio dependence. For the SDS/BEO solution with a molar ratio of 5:1, large loose irregular aggregates, vesicles, and long thread-like micelles are formed in succession with the increase of the total SDS and BEO concentration. Because BEO has two positive charges, the SDS/BEO solution may consist of the (SDS) 2 −BEO gemini-type complex, the SDS− BEO complex and extra SDS. The aggregation ability and surface activity of the SDS/BEO mixture exhibit the characteristics of gemini-type surfactants. Along with the results of DSC and 1 H NMR, the (SDS) 2 −BEO gemini-type structure is confirmed to exist in the system. This work provides an approach to construct the surfactant systems with the characteristics of gemini surfactants through intermolecular interaction between a two-charged organic salt and oppositely charged single-chain surfactants. ■ INTRODUCTIONSurfactant molecules can self-assemble into highly organized aggregates with various kinds of morphologies in aqueous solutions, including spherical micelles, worm-like or thread-like micelles, vesicles, bilayers, nanotubes, and so on. 1−3 All of these aggregates are related to the wide applications of surfactants. Researchers have made great efforts to develop highly efficient surfactants with various molecular structures. Gemini surfactants are one kind of the highly efficient surfactants. Compared with conventional single-chain surfactants, gemini surfactants show many unique properties, such as high surface activity, low critical micelle concentrations (CMC), unusual aggregate morphologies, and so on. 4−6 However, complicated synthesis procedures limit the development and industrial applications of the novel surfactants. If gemini-type surfactants can be constructed through intermolecular interaction between single-chain surfactants and a gemini-type connection molecule, it will open a new facile approach to obtain highly efficient surfactants. An organic salt with two connecting points to ionic surfactants should be a possible choice as a gemini-type connection molecule.A kind of organic salt can be constructed by aromatic groups and several charged substituents. Recently, Nalluri and Ravoo 7 applied the photoisomerization of a bifunctional noncovalent linker molecule to induce and reverse molecular recognition and adhesion of vesicles. The linker molecule was constructed by two functional azobenzenes covalently bound with a hydrophilic spacer. Being inspired by the linker molecule, we realized that gemini-type surfactants could be constructed by a "gemini-type" organic salt, in w...

Two peptide-amphiphiles (PAs), 2C(12)-Lys-Aβ(12-17) and C(12)-Aβ(11-17)-C(12), were constructed with two alkyl chains attached to a key fragment of amyloid β-peptide (Aβ(11-17)) at different positions. The two alkyl chains of 2C(12)-Lys-Aβ(12-17) were attached to the same terminus of Aβ(12-17), while the two alkyl chains of C(12)-Aβ(11-17)-C(12) were separately attached to each terminus of Aβ(11-17). The self-assembly behavior of both the PAs in aqueous solutions was studied at 25 °C and at pHs 3.0, 4.5, 8.5, and 11.0, focusing on the effects of the attached positions of hydrophobic chains to Aβ(11-17) and the net charge quantity of the Aβ(11-17) headgroup. Cryogenic transmission electron microscopy and atomic force microscopy show that 2C(12)-Lys-Aβ(12-17) self-assembles into long stable fibrils over the entire pH range, while C(12)-Aβ(11-17)-C(12) forms short twisted ribbons and lamellae by adjusting pHs. The above fibrils, ribbons, and lamellae are generated by the lateral association of nanofibrils. Circular dichroism spectroscopy suggests the formation of β-sheet structure with twist and disorder to different extents in the aggregates of both the PAs. Some of the C(12)-Aβ(11-17)-C(12) molecules adopt turn conformation with the weakly charged peptide sequence, and the Fourier transform infrared spectroscopy indicates that the turn content increases with the pH increase. This work provides additional basis for the manipulations of the PA's nanostructures and will lead to the development of tunable nanostructure materials.

This work studied the interactions of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with cationic ammonium surfactants and anionic sulfate or sulfonate surfactants of different oligomeric degrees, including cationic monomeric DTAB, dimeric CCCBr, and trimeric DDAD as well as anionic monomeric SDS, dimeric CCC(SO), and trimeric TED-(CSONa). The partition coefficient P of these surfactants between the DOPC vesicles and water was determined with isothermal titration microcalorimetry (ITC) by titrating concentrated DOPC solution into the monomer solution of these surfactants. It was found that the P value increases with the increase of the surfactant oligomeric degree. Moreover, the enthalpy change and the Gibbs free energy for the transition of these surfactants from water into the DOPC bilayer become more negative with increasing the oligomeric degree. Meanwhile, the calcein release experiment proves that the surfactant with a higher oligomeric degree shows stronger ability of changing the permeability of the DOPC vesicles. Furthermore, the solubilization of the DOPC vesicles by these oligomeric surfactants was studied by ITC, turbidity, and dynamic light scattering, and thus the phase boundaries for the surfactant/lipid mixtures have been determined. The critical surfactant to lipid ratios for the onset and end of the solubilization for the DOPC vesicles derived from the phase boundaries decrease remarkably with increasing the oligomeric degree. Overall, the surfactant with a larger oligomerization degree shows stronger ability in incorporating into the lipid bilayer, altering the membrane permeability and solubilizing lipid vesicles, which provides comprehensive understanding about the effects of structure and shape of oligomeric surfactant molecules on lipid-surfactant interactions.

The influence of perfume molecules on the self-assembly of the anionic surfactant sodium dodecyl sulfate (SDS) and their localization in SDS micelles have been investigated by ζ potential, small angle X-ray scattering (SAXS), one- and two-dimensional NMR and isothermal titration microcalorimetry (ITC). A broad range of perfume molecules varying in octanol/water partition coefficients P are employed. The results indicate that the surface charge, size and aggregation number of the SDS micelles strongly depend on the hydrophobicity/hydrophilicity degree of perfume molecules. Three distinct regions along the log P values are identified. Hydrophilic perfumes (log P < 2.0) partially incorporate into the SDS micelles and do not lead to micelle swelling, whereas hydrophobic perfumes (log P > 3.5) are solubilized close to the end of the hydrophobic chains in the SDS micelles and enlarge the micelles with higher ζ potential and a larger aggregation number. The incorporated fraction and micelle properties show increasing tendency for the perfumes in the intermediate log P region (2.0 < log P < 3.5). Besides, the molecular conformation of perfume molecules also affects these properties. The perfumes with a linear chain structure or an aromatic group can penetrate into the palisade layer and closely pack with the SDS molecules. Furthermore, the thermodynamic parameters obtained from ITC show that the binding of the perfumes in the intermediate log P region is more spontaneous than those in the other two log P regions, and the micellization of SDS with the perfumes is driven by entropy.