A new set of amphiphilic tertiary amine N‐oxides has been prepared and their self‐assembly properties observed in aqueous solution by tensiometry, dynamic and static light scattering. X‐ray crystallographic analysis of parent amines and sulfoxide congeners indicates the formation of hydrogen‐bonded dimers as the primary assembly unit for formation of vesicles in preference to the compact micelles typical of lauryl dimethylamine N‐oxide (LDAO). 6‐Benzyloxy‐N,N′‐bis(5‐diethylaminopentylamine oxide)[1,3,5]triazine‐2,4‐diamine forms a 1 μm vesicle observed to entrap fluorescein. The [1,3,5]triazine core thus allows variation of the new self‐assembled structures from nano‐ to micrometre length scales. 相似文献
The preparation of long‐term‐stable giant unilamellar vesicles (GUVs, diameter ≥1000 nm) and large vesicles (diameter ≥500 nm) by self‐assembly in THF of the crystalline‐b‐coil polyphosphazene block copolymers [N=P(OCH2CF3)2]n‐b‐[N=PMePh]m ( 4 a : n=30, m=20; 4 b : n=90, m=20; 4 c : n=200, m=85), which combine crystalline [N=P(OCH2CF3)2] and amorphous [N=PMePh] blocks, both of which are flexible, is reported. SEM, TEM, and wide‐angle X‐ray scattering experiments demonstrated that the stability of these GUVs is induced by crystallization of the [N=P(OCH2CF3)2] blocks at the capsule wall of the GUVS, with the [N=PMePh] blocks at the corona. Higher degrees of crystallinity of the capsule wall are found in the bigger vesicles, which suggests that the crystallinity of the [N=P(OCH2CF3)2] block facilitates the formation of large vesicles. The GUVs are responsive to strong acids (HOTf) and, after selective protonation of the [N=PMePh] block, they undergo a morphological evolution to smaller spherical micelles in which the core and corona roles have been inverted. This morphological evolution is totally reversible by neutralization with a base (NEt3), which regenerates the original GUVs. The monitoring of this process by dynamic light scattering allowed a mechanism to to be proposed for this reversible morphological evolution in which the block copolymer 4 a and its protonated form 4 a+ are intermediates. This opens a route to the design of reversibly responsive polymeric systems in organic solvents. This is the first reversibly responsive vesicle system to operate in organic media. 相似文献
The self‐assembly of 4′‐hydroxy‐biphenyl‐4‐carboxylic acid (H2hbc), 4, 4′‐bipyridine (4, 4′‐bpy) with a cobalt salt under hydrothermal conditions yielded a novel dinuclear cobalt(II) coordination polymer, {[Co(Hhbc)2(4, 4′‐bpy)] · H2O}n ( 1 ), where the coordinating polymeric chains are connected together through hydrogen bonding into a 3D framework of the primitive cubic ( pcu ) topology. Two pcu frameworks are interweaved into a 3D twofold Class Ia interpenetrating array. 相似文献
Polymerization‐induced self‐assembly (PISA) was employed to compare the self‐assembly of different amphiphilic block copolymers. They were obtained by emulsion polymerization of styrene in water using hydrophilic poly(N‐acryloylmorpholine) (PNAM)‐based macromolecular RAFT agents with different structures. An average of three poly (ethylene glycol acrylate) (PEGA) units were introduced either at the beginning, statistically, or at the end of a PNAM backbone, resulting in formation of nanometric vesicles and spheres from the two former macroRAFT architectures, and large vesicles from the latter. Compared to the spheres obtained with a pure PNAM macroRAFT agent, composite macroRAFT architectures promoted a dramatic morphological change. The change was induced by the presence of PEGA hydrophilic side‐chains close to the hydrophobic polystyrene segment. 相似文献
Summary: Amphiphilic triblock copolymers (PEOx‐b‐PDMSy‐b‐PEOx) with different block lengths were synthesized and multi‐morphological complex crew‐cut, star‐like, and short‐chain aggregates were prepared by self‐assembly of the given copolymers. The morphologies and dimensions of the aggregates can be well controlled by variation of the preparation conditions. TEM, SEM, FFR‐TEM, and LLS studies show the resulting morphologies range from LCMs, unilamellar or multilayer vesicles, LCVs, porous spheres to nanorods.
TEM images of the vesicles formed from PEO‐b‐PDMS‐b‐PEO. 相似文献
Here, the formation of giant enzyme‐degradable polymersomes using the electroformation method is reported. Poly(ethylene glycol)‐block‐poly(ε‐caprolactone) polymersomes have been shown previously to be attractive candidates for the detection of bacterial proteases and protease mediated release of encapsulated reporter dyes and antimicrobials. To maximize the efficiency, the maximization of block copolymer (BCP) vesicle size without compromising their properties is of prime importance. Thus, the physical‐chemical properties of the BCP necessary to self‐assemble into polymeric vesicles by electroformation are first identified. Subsequently, the morphology of the self‐assembled structures is extensively characterized by different microscopy techniques. The vesicular structures are visualized for giant polymersomes by confocal laser scanning microscopy upon incorporation of reporter dyes during the self‐assembly process. Using time correlated single photon counting and by analyzing the fluorescence decay curves, the nanoenvironment of the encapsulated fluorophores is unveiled. Using this approach, the hollow core structure of the polymersomes is confirmed. Finally, the encapsulation of different dyes added during the electroformation process is studied. The results underline the potential of this approach for obtaining microcapsules for subsequent triggered release of signaling fluorophores or antimicrobially active cargo molecules that can be used for bacterial infection diagnostics and/or treatment. 相似文献
Two novel nonsymmetrical disc‐shaped molecules 1 and 2 based on 3,3′‐bis(acylamino)‐2,2′‐bipyridine units were synthesized by means of a statistical approach. Discotic 1 possesses six chiral dihydrocitronellyl tails and one peripheral phenyl group, whereas discotic 2 possesses six linear dodecyloxy tails and one peripheral pyridyl group. Preorganization by strong intramolecular hydrogen bonding and subsequent aromatic interactions induce self‐assembly of the discotics. Liquid crystallinity of 1 and 2 was determined with the aid of polarized optical microscopy, differential scanning calorimetry, and X‐ray diffraction. Two columnar rectangular mesophases (Colr) have been identified, whereas for C3‐symmetrical derivatives only one Colr mesophase has been found. 1 In solution, the molecularly dissolved state in chloroform was studied with 1H NMR spectroscopy, whereas the self‐assembled state in apolar solution was examined with optical spectroscopy. Remarkably, these desymmetrized discotics, which lack one aliphatic wedge, behave similar to the symmetric parent compound. To prove that the stacking behavior of discotics 1 and 2 is similar to that of reported C3‐symmetrical derivatives, a mixing experiment of chiral 1 with C3‐symmetrical 13 has been undertaken; it has shown that they indeed belong to one type of self‐assembly. This helical J‐type self‐assembly was further confirmed with UV/Vis and photoluminescence (PL) spectroscopy. Eventually, disc 2 , functionalized with a hydrogen‐bonding acceptor moiety, might perform secondary interactions with molecules such as acids. 相似文献
This paper presents results from a series of pulsed field gradient (PFG) NMR studies on lipophilic guanosine nucleosides that undergo cation‐templated assembly in organic solvents. The use of PFG‐NMR to measure diffusion coefficients for the different aggregates allowed us to observe the influences of cation, solvent and anion on the self‐assembly process. Three case studies are presented. In the first study, diffusion NMR confirmed formation of a hexadecameric G‐quadruplex [G 1 ]16 ? 4 K+ ? 4 pic? in CD3CN. Furthermore, hexadecamer formation from 5′‐TBDMS‐2′,3′‐isopropylidene G 1 and K+ picrate was shown to be a cooperative process in CD3CN. In the second study, diffusion NMR studies on 5′‐(3,5‐bis(methoxy)benzoyl)‐2′,3′‐isopropylidene G 4 showed that hierarchical self‐association of G8‐octamers is controlled by the K+ cation. Evidence for formation of both discrete G8‐octamers and G16‐hexadecamers in CD2Cl2 was obtained. The position of this octamer–hexadecamer equilibrium was shown to depend on the K+ concentration. In the third case, diffusion NMR was used to determine the size of a guanosine self‐assembly where NMR signal integration was ambiguous. Thus, both diffusion NMR and ESI‐MS show that 5′‐O‐acetyl‐2′,3′‐O‐isopropylidene G 7 and Na+ picrate form a doubly charged octamer [G 7 ]8 ? 2 Na+ ? 2 pic? 9 in CD2Cl2. The anion's role in stabilizing this particular complex is discussed. In all three cases the information gained from the diffusion NMR technique enabled us to better understand the self‐assembly processes, especially regarding the roles of cation, anion and solvent. 相似文献
An organic–inorganic molecular hybrid containing the Dawson polyoxometalate, ((C4H9)4N)5H‐ [P2V3W15O59(OCH2)3CNHCOC15H31], was synthesized and its surfactant‐like amphiphilic properties, represented by the formation of bilayer vesicles, were studied in polar solvents. The vesicle size decreases with both decreasing hybrid concentration and with increasing polarity of the solvent, independently. The self‐assembly behavior of this hybrid can be controlled by introducing different counterions into the acetonitrile solutions. The addition of ZnCl2 and NaI can cause a gradual decrease and increase of vesicular sizes, respectively. Tetraalkylammonium bromide is found to disassemble the vesicle assemblies. Moreover, the original counterions of the hybrid can be replaced with protons, resulting in pH‐dependent formation of vesicles in aqueous solutions. The hybrid surfactant can further form micro‐needle structures in aqueous solutions upon addition of Ca2+ ions. 相似文献
Novel poly[Mn(H2O)(dmb)(muco)] ( 1 ) (H2muco = trans,trans‐muconic acid; dmb = 5,5′‐dimethyl‐2,2′‐bipyridine) was obtained by self‐assembly, one‐pot, solution reaction. 1 crystallizes in a monoclinic system with P21 space group and forms an infinite one‐dimensional (1D) polymer. Remarkably, the six‐coordinate MnII display a rare distorted trigonal prismatic configuration. This unusual coordination arrangement appears to be acquired due to the supramolecular interactions of the polymeric structure of 1 , mainly throughout hydrogen bonding, giving rise to a 2D framework. Magnetic properties measurements reveal that 1 possesses weak antiferromagnetic interactions with θ(C–W) = –1.0 K and J = 458 cm–1. 相似文献
Visible‐ and red‐light responsive vesicles were prepared by incorporating a ruthenium aqua complex having two alkyl chains on tridentate and asymmetrical bidentate ligands (proximal‐ 2 : [Ru(C10tpy)(C10pyqu)OH2]2+, C10tpy=4′‐decyloxy‐2,2′;6′,2“‐terpyridine, C10pyqu=2‐[2′‐(6′‐decyloxy)‐pyridyl]quinoline). The ruthenium complex of proximal‐ 2 with closed alkyl chain geometry and a cylinder‐like molecular shape exhibited photoisomerization to distal‐ 2 with an open alkyl chain geometry and a cone‐like shape, both in an aqueous solution and in vesicle dispersions. We observed that light irradiation of giant vesicles containing proximal‐ 2 induced diverse morphological changes. 相似文献
The behavior of self‐assembly processes of nanoscale particles on plasma membranes can reveal mechanisms of important biofunctions and/or intractable diseases. Self‐assembly of citrate‐coated gold nanoparticles (cAuNPs) on liposomes was investigated. The adsorbed cAuNPs were initially fixed on the liposome surfaces and did not self‐assemble below the phospholipid phase transition temperature (Tm). In contrast, anisotropic cAuNP self‐assembly was observed upon heating of the composite above the Tm, where the phospholipids became fluid. The number of self‐assembled NPs is conveniently controlled by the initial mixing ratio of cAuNPs and liposomes. Gold nanoparticle protecting agents strongly affected the self‐assembly process on the fluidic membrane. 相似文献
Titanium dioxide (TiO2) spheres are potential candidates to fabricate three‐dimensional (3D) photonic crystals owing to their high refractive index and low absorption in the visible and near‐infrared regions. Here, TiO2 spheres with both high surface charge density and uniform size, which are necessary for the self‐assembly of TiO2 spheres, have been prepared by means of sol–gel methods in ethanol in the presence of thioglycolic acid as ligand. Thioglycolic acid, which contains two functional groups, not only acts as coordinating ligand for stabilizing and controlling the growth of TiO2 spheres but also endows the resulting TiO2 spheres with high charge density as based on ζ ‐potential analysis when the pH of the TiO2 aqueous dispersion was 6.5 or higher. The SEM images illustrate that the diameter of the prepared TiO2 spheres can be tuned from 100 to 300 nm by simply controlling the concentration of H2O. FTIR spectra confirm that thioglycolic acid bonded to the surface of TiO2 spheres through carboxylic groups. As anticipated, the obtained TiO2 spheres could self‐assemble to form a 3D opal photonic crystal structure by means of a simple gravity sedimentation method. Then the TiO2 spheres in the 3D opal photonic crystal structure were able to transform into a pure anatase phase by annealing at different temperatures. 相似文献
Summary: Hollow copper nanoparticle (Cu‐NP) spheres with different wall thicknesses were prepared with organic and inorganic colloids as core combining self‐assembly and electroless Cu deposition techniques. The hollow Cu‐NP spheres made from polymeric colloids possessed a thicker wall but were easy to break in the removal of the core by THF, while those from SiO2 colloids had thinner wall and remained intact in the removal of the core by HF.