Mixed micelles formed by SDS and a bolaamphiphile with carbohydrate headgroups

The formation of micelles in aqueous mixtures of a carbohydrate-based bolaamphiphile and sodium dodecyl sulfate (SDS) is investigated by surface tension and small-angle neutron scattering. The obtained values of critical micelle concentration (CMC) are analyzed within the framework of regular solution theory. Synergetic interactions between the bolaamphiphile and SDS are observed (parameter beta is negative; a minimum in the plot CMC vs composition). SANS data are collected for mixtures containing protonated and deuterated SDS. This gives us the possibility to conclude that mixed micelles with a homogeneous distribution of surfactant molecules within the micelle are formed. The shape of the micelles is found to be slightly oblate.     

Coagulation and stabilization of sterically functionalized magnetite nanoparticles in an organic solvent with different technical polymers

Single crystalline zinc tin oxide (ZTO) nanocrystallites were prepared at room temperature through association with a peptide-containing bolaamphiphile molecule. The bolaamphiphile molecules self-assembled to form spherical structures with creation of ZTO nanocrystallites inside. ZTO nanocrystallite synthesis was achieved only when the bolaamphiphile molecule was present, while a mixture of amorphous Sn and Zn precipitates was formed in the absence of the bolaamphiphile molecule. The bolaamphiphile molecule is thought to stabilize the Zn(2+) and Sn(4+) precursor ions by ligation and to induce subsequent condensation forming crystalline ZTO. The ZTO formation was achieved only at a strong acidic condition that promotes dissociation and ionization of Zn and Sn precursors and represses formation of ZnO and H(2)SnO(3). The prepared ZTO nanocrystallites had almost the same band gap energy as ZTO nanoparticles prepared by the conventional hydrothermal process. The outcomes of this study indicate that the controlled mineralization of metal precursor ions in a peptide-containing bolaamphiphile molecule suspension can be an alternative method to synthesize metal oxides at room temperature, while maintaining their crystalline structure and optoelectrical properties.     

pH-Controlled Supramolecular Self-Assembly of Naphthalenediimide Appended l-Alanine and Ethylenediamine Asymmetric Bolaamphiphile

Design, synthesis and characterization of novel (2S)-2-[7-(2-aminoethyl)-1,3,6,8-tetraoxo-3,6,7,8-tetrahydrobenzo[lmn][3,8]phenanthrolin-2(1H)-yl]propanoic acid ( 1 ) bolaamphiphile, which combine naphthalene diimide (NDI) appended with l -alanine at one end of imide and ethylenediamine at the other end. An l -alanine bearing NDI-based asymmetric bolaamphiphile self-assembled at various pH ranging from 2 to 10 forms a variety of supramolecular nanostructures. The UV-Vis and emission spectroscopic techniques employed for the optical and photophysical properties study of bolaamphiphile 1 at various pH values. It was revealed that the change in pH alters both the optical and photophysical properties of bolaamphiphile 1 . Theoretical calculations used to investigate the electronic properties of the bolaamphiphile 1 . Dynamic light scattering experiments displayed formation of aggregates in solution and scanning electron microscopy (SEM) was used to visualize the nanostructures formed on silicon wafers. Furthermore, the X-ray diffraction was used to determine the nanostructure's packing properties i. e. crystalline/amorphous. Experimental circular dichroism (CD) spectroscopy results inferred and revealed the induction of chirality into the supramolecular systems, which was shown to be pH dependent. This study clearly demonstrates the manipulation of pH can control/tune chiral supramolecular structures and provide future methods for the development of chiral recognition and catalysis study.     

Self-assembled helical spherical-nanotubes from an L-glutamic acid based bolaamphiphilic low molecular mass organogelator

An L-glutamic acid based bolaamphiphile was observed to self-assemble into a novel "helical spherical-nanotube" with a molecular monolayered structure within a tubular wall.     

Flat orientation of hydrophobic cores induced by two-dimensional confinement of flexible bolaamphiphiles at the air-water interface

We designed and synthesized a new bolaamphiphile consisting of a biphenyl core, flexible trisiloxane spacers, and terminal ammonium groups. The compression of the trisiloxane-containing bolaamphiphile at the air-water interface led to the formation of monolayer films with the hydrophobic rigid core lying flat on the film surface. Such monolayer structures were formed through the compression-induced conformational change of the flexible bolaamphiphile from an extended state to a folded one as confirmed by surface pressure-area isotherm measurements, water contact angle measurements, atomic force microscopy, and UV-vis spectroscopy.     

Cross-Section Molecular Imaging of Supramolecular Microtubes with Contact Atomic Force Microscopy

Bent molecules, distorted layers, columnar domains, and tube membranes (shown schematically in the picture): These hierarchical layers were directly visualized by contact atomic force microscopy along the long axes of the molecules aligned within microtubes made up of bolaamphiphile 1 by self-assembly.     

Synthesis and properties of a novel bolaamphiphile surfactant derived from proline

A novel bolaamphiphile surfactant N,N0-(octane-1,8-diyl)bis(pyrrolidine-2-carboxamide)(DAOP), was designed and synthesized from proline and 1,8-diaminooctane, as the hydrophilic part and hydrophobic part, respectively. After separation and purification, the structures of the synthesized bola surfactants were verified by IR, MS and~1 H NMR. The p Kawas measured by a titration experiment, the turbidity was determined using a Shimadzu UV-1750 spectrophotometer, and the critical micelle concentration(CMC)values of the synthesized surfactants in water were obtained using the conductivity and fluorescence probe measurements. The synthesized bolaamphiphile surfactants demonstrate the ability of selfassemble to form vesicles that were confirmed with dynamic light scattering and transmission electron microscopy. The results showed that the novel bolaamphiphile surfactant derived from proline might potentially be an excellent carrier for drug delivery.     

Structure-property relationship in stimulus-responsive bolaamphiphile hydrogels

The formation of temperature-, concentration-, and pH-responsive hydrogels composed of the symmetric long-chain bolaamphiphile dotriacontane-1,1'-diyl bis[[2-(dimethylammonio)ethyl]phosphate] (Me(2)PE-C32-Me(2)PE) was investigated by rheological, scattering, and spectroscopic techniques. At pH 5, this bolaamphiphile is known to form a dense network of helically structured nanofibers (K?hler et al. Soft Matter 2006, 2, 77-86). Rheological measurements and dynamic light scattering were used to describe the macroscopic behavior of the hydrogels. Small-angle neutron scattering (SANS) and time-resolved static light scattering were applied to get information about the morphology of the self-assembled aggregates. Finally, solid-state 31P NMR spectroscopy was used to gain insight into the mobility of the bolaamphiphile molecules within the fiber aggregates. In comparison with the previously examined trimethylammonio analogue PC-C32-PC, which forms temperature-dependent hydrogels, Me(2)PE-C32-Me(2)PE exhibits additional concentration- and pH-dependent gelling properties. The significantly higher stability of the Me(2)PE-C32-Me(2)PE hydrogel is supported by the SANS data, which indicate the presence of fiber aggregates up to 50 degrees C.     

规则溶液理论应用于bola/SDS混合体系的研究

以规则溶液理论研究了bola型阳离子两亲分子与十二烷基硫酸钠（SDS）混合体系的表面和胶团相互作用.相互作用参数的数值表明, bola分子与SDS在胶团中和溶液表面都发生了强烈的相互作用,这种相互作用的强度与普通季铵盐/烷基硫酸钠混合体系相当.这说明bola分子与SDS混合体系中的协同作用主要是由亲水基之间的静电相互作用产生的, 而bola分子结构中疏水部分对相互作用没有显著影响.     

Synthesis of unsymmetrical spin-labelled bolaamphiphiles

This work presents the efficient synthesis of a novel spin-labelled bolaamphiphile bearing sugar and cationic polar heads. Preliminary ESR studies were conduced both in CH₂Cl₂ and water and have confirmed that this methodology can be used to study the transversal rotation (flip-flop) dynamic of membrane involving such bolaamphiphiles.     

Compression induced helical nanotubes in a spreading film of a bolaamphiphile at the air/water interface

Inspired by the elegant helical structures endowed by mother nature, we designed an L-glutamic acid terminated bolaamphiphile and obtained helical nanotubes through the manipulation on the two-dimensional Langmuir films at the air/water interface. It has been found that on the subphase with a pH value lower than 3, stable monolayers with plateau regions were obtained for the bolaamphiphile. Although a flat and uniform morphology was observed for the film deposited at a surface pressure below the plateau region, helical nanotube structures were obtained when the film was compressed over the plateau region. It was suggested that the compression of the monolayer at the air/water interface caused the one end of the bolaamphiphile to leave from the water surface and form an intermediate monolayer in which one end group attached on the water surface and the other extruded in the air. Such an intermediate monolayer subsequently rolled into a helical structure due to the chiral nature of the L-glutamic acid headgroup.     

Molecular packing parameter in bolaamphiphile solutions: adjustment of aggregate morphology by modifying the solution conditions

The geometrical rule of molecular packing parameters in a bolaamphiphile solution was tested with experimental results. By modifying the solution conditions to change the molecular packing parameters, the morphology of the aggregate was successfully manipulated in a single-chain bolaamphiphile, disodium phenyl-1,4-bis (oxyhexanoate) (i.e., C6PhC6Na2 solution). Micelle-vesicle-tube transformation was observed by changing the pH and the addition of NaBr or octanol. In the mixed systems of oppositely charged bola/surfactants, the molecular packing parameter's role is related to the mixing ratio.     

Detection of complementary hydrogen bond complexes in water by electrospray ionization-Fourier-transform ion cyclotron resonance mass spectrometry

Complementary base paired complex formation of a thymidine-appended bolaamphiphile with adenosine derivatives was able to be detected with high resolution and high sensitivity in aqueous solutions by electrospray ionization-Fourier-transform ion cyclotron resonance mass (ESI-FTICR MS) spectrometry.     

Fluorescence microscopic investigation on morphological changes of giant multilamellar vesicles induced by amphiphilic additives

Adding an artificial bolaamphiphile to a dispersion of giant multilamellar vesicles (GMVs) made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) induced a cup-shaped deformation in GMVs accompanied by partial extrusion of the inner vesicle; thereafter, the deformed vesicles returned to their original shape. On the other hand, when the artificial bolaamphiphile together with a surfactant was added to the vesicular dispersion, these deformation and reformation dynamics were transmitted from the outer membranes in GMVs to the inner membranes until an intact inner vesicle was extruded out of the outer membrane. The microscopic aspects of these processes were investigated using amphiphiles tagged with individual fluorophores.     

Temperature-dependent self-assembly and mixing behavior of symmetrical single-chain bolaamphiphiles

The temperature-dependent self-assembly and the mixing behavior of symmetrical single-chain bolaamphiphiles with different polymethylene chain lengths and different headgroup structures were investigated in water by differential scanning calorimetry (DSC), cryo transmission electron microscopy (cryo-TEM), and small angle neutron scattering (SANS). The even-numbered polymethylene-1,omega-bis(phosphocholines) (PC-C n-PC) are known to form nanofibers composed of stretched molecules with an all- trans alkyl chain conformation (Drescher, S.; Meister, A.; Blume, A.; Karlsson, G.; Almgren, M.; Dobner, B. Chem.Eur. J. 2007, 13, 5300-5307). The odd-numbered analogues were synthesized to study a possible even-odd effect of these bolaamphiphiles during their aggregation in water. In addition to these bolaamphiphiles with phosphocholine headgroups, a new series of polymethylene-1,omega-bis(phosphodimethylethanolamines) (Me2PE-Cn-Me2PE) with smaller headgroup sizes was synthesized. These bolaamphiphiles show an additional fiber-fiber transition when the alkyl chain length exceeds 26 carbon atoms. The mixing behavior of both types of bolaamphiphiles indicates that differences in the alkyl chain length up to six carbon atoms are tolerated within the fiber structure. The mixing of two Me2PE-Cn-Me2PE or PC-Cn-PC type bolaamphiphiles with different alkyl chain lengths offers the possibility to adjust the temperature, where the cross-linking of the fibers is disrupted and where the fibers break apart. As a consequence, temperature switchable hydrogels are obtained that can be fine-tuned for drug delivery applications. The comparison with dotriacontane-1,32-diyl-bis[2-(methylammonio)-ethylphosphate] (MePE-C32-MePE), a new bolaamphiphile with even smaller phosphomonomethylammonio headgroups, illustrates the importance of the headgroup size for the aggregation behavior. This bolaamphiphile self-assembles exclusively into lamellar structures, and this aggregate type persists in mixtures with the fiber forming Me2PE-C32-Me2PE.     

Optical Properties and Photopolymerization of Liquid Crystalline (Acetyl) (Ethyl) Cellulose/Acrylic Acid System

The structure and properties of a chiral nematic phase, which reflects one hand of circularly polarized light in a narrow region of wavelength, of fully acetylated (ethyl) cellulose [(acetyl) (ethyl) cellulose, AEC] in acrylic acid (AA) were studied in comparison with (ethyl) cellulose (EC). AEC mesophase formed right-handed chiral nematic structure while EC formed left-handed one. AEC mesophase showed higher birefringence and reflection intensity. The relationship between the reflection wavelength and the polymer concentration was negatively correlated for both AEC and EC mesophases. The relationship between the reflection wavelength and the molecular weight was also negative for AEC mesophase whereas positive for EC mesophase. AEC mesophase was solidified by photopolymerization of AA moiety. It was revealed that the optical properties of AEC mesophase could be preserved by photopolymerization, since the resulting solid material reflects selectively one hand of circularly polarized light.     

Hydrogen-bonding-mediated vesicular assembly of functionalized naphthalene-diimide-based bolaamphiphile and guest-induced gelation in water

This paper describes the spontaneous vesicular assembly of a naphthalene-diimide (NDI)-based non-ionic bolaamphiphile in aqueous medium by using the synergistic effects of π-stacking and hydrogen bonding. Site isolation of the hydrogen-bonding functionality (hydrazide), a strategy that has been adopted so elegantly in nature, has been executed in this system to protect these moieties from the bulk water so that the distinct role of hydrogen bonding in the self-assembly of hydrazide-functionalized NDI building blocks could be realized, even in aqueous solution. Furthermore, the electron-deficient NDI-based bolaamphiphile could engage in donor-acceptor (D-A) charge-transfer (CT) interactions with a water-insoluble electron-rich pyrene donor by virtue of intercalation of the latter chromophore in between two NDI building blocks. Remarkably, even when pyrene was located between two NDI blocks, intermolecular hydrogen-bonding networks between the NDI-linked hydrazide groups could be retained. However, time-dependent AFM studies revealed that the radius of curvature of the alternately stacked D-A assembly increased significantly, thereby leading to intervesicular fusion, which eventually resulted in rupturing of the membrane to form 1D fibers. Such 2D-to-1D morphological transition produced CT-mediated hydrogels at relatively higher concentrations. Instead of pyrene, when a water-soluble carboxylate-functionalized pyrene derivative was used as the intercalator, non-covalent tunable in-situ surface-functionalization could be achieved, as evidenced by the zeta-potential measurements.     

Multilayer structure of an unsymmetrical monolayer lipid membrane with a 'head-to-tail' interface

A synthetic unsymmetrical 1-galactosamide bolaamphiphile self-assembles in methanol to form a multilayer structure comprising unsymmetrical monolayer lipid membranes linked via a sugar-carboxylic acid H-bonding interface.     

Studies on hydroquinone based maleate bolaamphiphile organogels and their drug formulations

Now a day’s there is an upsurge in topical gel formulations, they can be prepared by varying physico-chemical methods and provide better localized action. A maleate based symmetric bolaamphiphile was synthesized by using cost-effective starting materials under mild reaction condition. The gelation ability of bolaamphiphile in aqueous medium was examined for a series of organic solvents. In hexane, the gelator showed better gelation ability with relatively higher critical strain (54 Pa) values. Further, the microscopic images of the gel revealed flakes like morphology, both the XRD and DFT studies revealed the presence of non covalent interactions. These gels showed a high internal-phase mole ratio of the topical drugs in the order of curcumin < salicylic acid < Ibuprofen. Formation of aqueous and organic gel-phase formulation may facilitate the topical medications for various applications related to ophthalmic and skin infections.     

Membrane dynamics of a myelin-like giant multilamellar vesicle applicable to a self-reproducing system

A real time observation of a myelin-like giant multilamellar vesicle (mGMV) revealed that it divided into relatively small mGMVs when an aqueous solution of an electrolyte was added. Furthermore, the mGMV showed a division process accompanied by the growth of the dividing mGMVs when a bolaamphiphile which was composed of an electrolyte unit and a vesicular amphiphile unit was added. This vesicular system can be regarded as a self-reproduction of mGMV, where the added amphiphile acts as a supplier of both the vesicular amphiphile and the division initiator.