Self-organized Materials Research Articles

T10 Polyhedral Oligomeric Silsesquioxane-Based Shape Amphiphiles with Diverse Head Functionalities via "Click" Chemistry.

Head diversification of shape amphiphiles not only broadens the scope of supramolecular engineering for new self-organizing materials but also facilitates their potential applications in high technologies. In this letter, T10 azido-functionalized polyhedral oligomeric silsesquioxane (POSS) nanoparticle was used to construct new shape amphiphiles via sequential "click" chemistry for addressing two issues: (1) new symmetry of T10 POSS head could enrich the self-assembly behaviors of shape amphiphiles, and (2) copper-catalyzed azide-alkyne cycloaddition (CuAAC)-based head functionalization strategy allows the introduction of diverse functionalities onto POSS heads, including bulky ligands (i.e., isobutyl POSS) and UV-attenuating ones (i.e., ferrocene and 4-cyano-4'-biphenyl). This study expands the library of POSS-based shape amphiphiles with numerous possibilities for head manipulations, offering an important step toward new shape amphiphiles beyond traditional hydrophobic/hydrophilic nature for potential applications in giant molecule-based nanoscience and technology.

Self-organized nanotube materials and their application in bioengineering

Although a large number of studies on organic nanotubes have focused on the molecular design of building blocks and their material function, there has been little research that has addressed the function of the nanochannels themselves, such as their encapsulation ability. The dimensions of self-assembled organic nanotubes (S-ONTs) are well compatible with those of diverse nanostructures, including proteins, organic, inorganic or metal nanoparticles, dendrimers, viruses and DNAs. S-ONTs can give rise to a novel research field of mesoscale host–guest science and engineering. More interestingly, S-ONTs can accommodate extremely small liquid volumes on the order of attoliters in their nanochannels. Focusing on the distinctive function and structural characteristics of these nanochannels, herein we describe the recent progress in research on the unique properties of nanochannels that can encapsulate, transport and release biomacromolecules as well as exert a confinement effect on water.

ChemInform Abstract: Nanostructured Solids — From Nano‐Glasses to Quantum Transistors

AbstractReview: 212 refs.

Time Resolved Study on Fabrication of Porous Alumina for Further Use to Generate Metallic Nano Catalyst

Porous anodic alumina (PAA) is one of the important nanostructured materials. This has gained exposure recently for applications in gas separation[1], drug delivery[2], bone fixation [3] and as a template for formation of nanostructures [4]. Anodic porous alumina is formed by the anodization of Aluminum, which is a self-organized material, to get a layer of nanoporous oxide [5]. This porous anodic aluminum (PAA) membrane consists of a ordered hexagonal arrangement of cells with a central pore per cell that elongates from top to bottom of the layer, resembling a honeycomb [6]. These pores are used as template for synthesis of 1dimensional (1D) nanostructure and hence the degree of ordering of these cell arrangements plays an important role in the homogeneity of the resulting nanomaterials. Present work focuses on study of anodization as function of time, to see the trend in pore size, pore density and degree of ordering of Anodized Aluminum oxide (PAA) membrane. Proper selection of anodization time and phases allow the tuning of self-ordering regime, control of local catastrophic phenomena and achievement of a more uniform growth. Afterward, self-assembled template has been used for the synthesis of novel ID nanostructure of tungsten trioxide by electroless deposition method. Scanning Electron Microscope (SEM) images depict uniform arrangment of tungsten trioxide nanowire. Internal diameter of formed nanowires is around 50 nm similar to porous diameter of PAA templates. Furthermore XRD patterns of nanowire indicate the presence of two crystalline forms of WO3 i.e. monoclinic and orthorhombic.

Mechanisms and shape predictions of nematic disclination branching under conical confinement

Liquid crystals (LCs) are self-organizing anisotropic viscoelastic soft materials that flow like viscous liquids and display anisotropies like crystals. When a nematic liquid crystal is confined to a capillary tube with strong anchoring conditions, disclination defects of higher (+1) and lower (+1/2) topological charges can coexist, connected through a defect branch point. The shape of the +1/2 disclination lines emanating from the branch point are functions of confinement and bulk elasticity. Previous work shows that nematic liquid crystals under cylindrical confinement display a radial (one +1 line)-to-planar polar (two +1/2 lines) defect texture transition through the nucleation and uniform motion of a disclination branch point. Here we present analysis, scaling and modeling based on a non-linear non-local nematic elastic equation that shows that a branch point also can be generated from disclinations in a liquid crystal confined to different conical geometries with homeotropic anchoring conditions. The cone aperture increases the bending stiffness but decreases the curvature of the disclination. These competing effects lead to a decrease in the total disclination curvature, increase in elastic energy and volume of the branching region. The results are summarized into power laws and integrated into a shape/energy diagram that reveals the effects of confinement and its gradient (cone angle) on disclination shape selection. These new findings are useful to assess the Frank elasticity of new nematic liquid crystals and to predict novel defect structures in complex confinement, including biological microfluidics and mesophase fiber spinning.

Microbial Biofabrication for Nanomedicine: Biomaterials, Nanoparticles and Beyond

Author for correspondence: Institut de Biotecnologia i de Biomedicina, Universitat Autonoma de Barcelona, Bellaterra, 08193 Barcelona, Spain and Department de Genetica i de Microbiologia, Universitat Autonoma de Barcelona, Bellaterra, 08193 Barcelona, Spain and CIBER en Bioingenieria, Biomateriales y Nanomedicina, Bellaterra, 08193 Barcelona, Spain antoni.villaverde@uab.cat Microbial biofabrication for nanomedicine: biomaterials, nanoparticles and beyond

On a roll

Populations of rolling particles have been shown to display unidirectional collective motion in a racetrack enclosure. Theoretical modelling suggests that hydrodynamic and electrostatic effects promote such behaviour. See Letter p.95 Collective motion can be observed in the natural world at all scales, from flocking birds to schooling fish and swarming bacteria, but it is difficult to capture such behaviour in simple physical models. Artificial 'active matter' systems that show collective behaviour usually rely on collisions, making the description of interactions complex. Denis Bartolo and colleagues have now developed a unique experimental system consisting of self-propelled rolling spheres that self-organize and move in one direction in a crowd of millions. The spheres 'sense' each other via straightforward hydrodynamic interactions so that all parameters can be easily calculated and tuned. This work demonstrates that genuine physical interactions at the individual level are sufficient to set homogeneous active populations into stable directed motion. The system could be used to model natural collective motion and to design new self-organized materials and swarming microrobots.

Self‐Assembled Supramolecular Channels: Toward Biomimetic Materials for Directional Translocation

This Personal Account summarizes the recent developments in the development of self-assembled supramolecular channels and their dimensional extension towards up-scaled self-organized materials. This Personal Account begins with a short, non-exhaustive description of artificial supramolecular channel systems that are involved in water-, proton-, and ion-transport processes through bilayer membranes. Then, these "all-made" artificial systems will be described as a source of inspiration, by presenting several breakthroughs over the last few years in the field of biomimetic supramolecular channel systems. Their inclusion in artificial polymeric/hybrid matrixes, which results in the formation of biomimetic artificial materials for directional translocation through channeling pathways, will be described in the last part of the Personal Account, with an emphasis on all of the efforts that are necessary to maintain their channel-transporting function within bilayer membranes under up-scaled operating conditions.

Multifunctional Dendritic Sialopolymersomes as Potential Antiviral Agents: Their Lectin Binding and Drug Release Properties

Polymer vesicles, commonly referred to as polymersomes, are self-organized materials that result from the self-assembly of amphiphilic copolymers in solution. Recently, there has been increasing interest in biomedical applications of polymersomes due to the different functions that can be imparted through encapsulation of molecules within the core or membrane or through the introduction of bioactive molecules to the polymersome surface. We describe here the development and study of poly(ethylene oxide)-polycaprolactone polymersomes designed to interact with influenza viruses at two different stages in the infection process. First, the conjugation of the sialic acid N-acetylneuraminic acid (Neu5Ac) to the polymersome surface was designed to inhibit the binding of viral hemagglutinin to sialic acids on host cells, thus preventing viral entry. Second, the incorporation of the neuraminidase inhibitor zanamivir into the polymersome core was designed to prevent the release of progeny virus from the host cells, thus inhibiting viral replication. With the aim of maximizing multivalent effects at the polymersome surface, polyester dendrons functionalized with Neu5Ac were synthesized and conjugated to polymersomes. Binding of the resulting dendritic sialopolymersomes to Limax flavus agglutinin was studied and compared to the sialodendron and a monovalent Neu5Ac derivative using an enzyme-linked lectin inhibition assay. It was found that while the sialodendron exhibited a 17-fold enhancement (per sialoside) relative to the small molecule, the dendritic sialopolymersomes resulted in an almost 2000-fold enhancement in binding affinity. It was also demonstrated that encapsulation of zanamivir into the dendritic sialopolymersomes could be performed with the same efficiency as for naked polymersomes to provide a drug loading of ~35 wt %. Drug release rates were similar for both systems with sustained release over a period of 4 days. Overall, these results suggest the promise of using a multifunctional polymersome system for interaction with and inhibition of influenza viruses.

Cross-linking of discotic tetraazaporphyrin dyes in 2 and 3 dimensions by “click” chemistry

An intrinsic shortcoming of self-organizing materials is their susceptibility to structural changes by mechanical forces and exposure to chemicals and radiation. Cross-linking of the molecules in the desired supramolecular structure is a generally applicable pathway to structurally more stable materials but is difficult to apply to self-organizing materials because the introduction of cross-linkable groups affects their self-organization and the process of cross-linking may alter the supramolecular structure of the preceding phase. Reported here are the synthesis, thermal properties, and cross-linking of octaalkylthio substituted tetraazaporphyrins that contain either eight terminal azide groups or eight terminal acetylene groups. Synthesis of these compounds requires the preparation of the azide and alkyne containing side-chains and their reaction with 1,2-dicyanoethylene-1,2-dithiolate to the corresponding maleodinitrile intermediates. All maleodinitriles are successfully converted to tetraazaporphyrins by the established Mg templated cyclotetramerization in typical yields of 60–70%. Thermal properties of the metal-free and copper(II) metallated tetraazaporphyrins were studied by thermal gravimetric analysis, polarized optical microscopy, differential scanning calorimetry, and variable temperature powder X-ray diffraction measurements. Azide substituted tetraazaporphyrins with trimethylene and hexamethylene spacers as well as acetylene derivatives with trimethylene spacers unexpectedly display columnar mesophases over ranges of temperature from 30 °C to 110 °C. A thermally activated cross-linking of a hexagonal columnar mesophase by cycloaddition at 65 °C is demonstrated for a 1 : 1 mixture of azide and acetylene derivatives. At this temperature the reaction progresses for up to 48 hours but renders the mesophase insoluble and stable to above 200 °C. The structure of the mesophase is surprisingly little affected by the cross-coupling process that reaches a conversion of 60% of all azide and acetylene groups based on IR measurements. Conversion of up to 80% of azide and acetylene groups is reached by copper catalysed cross-linking of a 1 : 1 mixture in solution to generate insoluble polymers. A similar degree of conversion is achieved by copper catalysed cross-linking of a 1 : 1 mixture as Langmuir film after 3 hours. However, transfer of intact cross-linked Langmuir films onto substrates was not successful.

Self-organized nanostructured materials of alkylated phthalocyanines and underivatized C60 on ITO

Clicking thiols onto a core fluorous phthalocyanine (Pc) platform yields alkyl and fluoroalkyl derivatives. The Zn(II) Pc with 16 thioalkanes self-organizes with fullerene C60 into nearly monodispersed nanoparticles when cast on ITO surfaces. Particle size and surface density is controlled by varying the Pc/fullerene ratio and concentration. Fluorescence quenching indicates electronic interaction between the component molecules in the films of nanoparticles. The strong supramolecular interactions between the Pc with 8 or 16 fluorous alkanes inhibit incorporation of the fullerene.

Cholesterol-aided construction of distinct self-organized materials from a luminescent gold(i)–isocyanide complex exhibiting mechanochromic luminescence

A cholesterol-functionalized gold(i)-isocyanide complex exhibiting mechanochromic luminescence properties was self-organized into distinct microscopic structures with different photoluminescence properties through vapor-diffusion of a poor solvent into its dichloromethane solution. The structure-optical property relationship of these microstructures could be related to the mechanically induced phase transition.

Room temperature self-organized gold nanoparticles materials for embedded electronic devices

In this study, we synthesize two different sizes of gold nanoparticles (NPs) with uniform size distribution. A novel technique of fabricating gold NPs embedded capacitor devices utilizing chemical self-assembled gold NPs has been developed. Room temperature process and uniform size distribution of gold NPs device are built and characterized. These electronic devices have lower leakage current, no metal diffusion problem, larger memory window, better charge retention time and following Fowler–Nordheim tunneling model. This method enables the possibility of future memory applications to fabricate devices with this simple and versatile technique based on the NPs assembly.

Properties of a Novel Siloxane-containing Epoxy Resin

To fabricate self-organized gradient material using bisphenol-A epoxy resin (E51) and siloxane, the properties of a novel synthesized siloxane-containing epoxy resin (SE) were investigated in advance. It is found that SE behaves like Newtonian fluid at low shear rates, while like non-Newtonian fluid at high shear rates. Similar to E51, SE is soluble in most solvents. Although curing process of two epoxy resins submits to first-order reaction kinetics, curing activity of SE is higher slightly. Contrary to the cured E51, the cured SE is hydrophobic and characterized by ductile fracture. It is also observed that the cured SE is more stable in thermal decomposition than the cured E51.

Preparation of hybrid ion channel membrane for recognizing and transporting sodium ion

A kind of self-organized hybrid material, 3-(ureidobenzene) propyltriethoxysilane, was obtained from 3-isocyanatopropyltriethoxysilane and aminobenzene with chloroform as solvent. The structure and the morphology of the materials were characterized by FTIR, 1H-NMR, and XRD methods. The ion channel membrane was obtained by coating the hybrid material onto the commercial polyacrylonitrile (PAN) supports via sol-gel process. The chemical structure and surface morphology of the membrane was characterized by ATR-FTIR and SEM separately. The ion transport property of the membrane was tested by our self-made device with the conductivity. SEM showed that the surface of ion channel membrane was dense and thickness of the dense layer was about 8.5 &mgr;m. The transport experiment suggested that the membrane had the properties of recognizing and transporting Na+.

Crystal structure, vibrational and optical properties of a new self-organized material containing iodide anions of bismuth(III), [C 6H 4(NH 3) 2] 2Bi 2I 10·4H 2O

Bismuth-iodide type zero-dimensional (0-D) organic/inorganic hybrid compound [C 6H 4(NH 3) 2] 2Bi 2I 10·4H 2O was synthesized and characterized by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group P2 1/ n, with a = 11.483(5), b = 12.896(5), c = 14.974(5) Å, β = 112.437°(5) and Z = 4; and consists of a p-phenylenediammonium dications, water molecules of crystallization in addition to the anion, which is built up of edge-sharing bioctahedra. The crystal packing is governed by I⋯ I electrostatic interactions and ionic N–H⋯I hydrogen bonds forming a self-assembled multiple zero-dimensional structure. Raman and infrared spectra of the title compound were recorded in the 0–170 and 400–4000 cm −1 frequency regions, respectively. An assignment of the observed vibration modes is reported. Optical transmission measurements on thin films of [C 6H 4(NH 3) 2] 2Bi 2I 10·4H 2O revealed two absorption bands at 2.84 and 2.4 eV. Photoluminescence measurements showed a strong emission line at 2.13 eV associated with radiative recombinations of excitons confined within the bioctahedra Bi 2 I 10 4 - .

EXPERIMENTAL ANALYSIS OF EROSIVE COHESIVE COASTLINE MORPHOLOGY

Laboratory experiments have been performed in a wave flume to investigate the coastal cliff recession under regular waves forcing. The different processes of the cliff erosion cycle are described and we focus on bottom evolution, which seem mostly depend on the surf similarity parameter ξ. We observed steep planar (ξ > 0.7), gentle planar (0.5 < ξ < 0.7) and bared (ξ < 0.5) profiles. We noticed different sandbar dynamics including either steady or unsteady self-sustained oscillating states. Then we estimate the role of the self-organized material on the cliff recession rate. We show that the cliff erosion increases with the wave energy flux and is stronger for a gentle planar profile than for a bared profile of bottom morphology. However, the cliff recession rate as a function of the cliff height is not monotonic due to a different dynamics of bottom morphologies.

Broad band tuning of the plasmonic resonance of gold nanoparticles hosted in self-organized soft materials

The extraordinary properties of reconfigurable soft materials are used to drive the resonance properties of noble metal nanoparticles, using an approach that puts a bridge between soft matter and plasmonics. Gold nanoparticles have been dissolved in a cholesteric liquid crystal and then infiltrated in a micro-periodic polymeric structure, realized by combining a holographic step and a microfluidic etching process. The spectral behavior of the nano-composite soft-structure has been investigated in the UV-Vis range for two different polarization directions of the impinging probe light. Correlation between the optical response and external perturbations (electric field, temperature variation) gives an outstanding example of broadband tuning of an “active” plasmon resonance.

Selected Peer-Reviewed Articles from International Conference on Advanced Functional Polymers and Self-Organized Materials 2008 (IC-PSM08)

Selected Peer-Reviewed Articles from International Conference on Advanced Functional Polymers and Self-Organized Materials 2008 (IC-PSM08)

PREPARATION OF ION CHANNEL MEMBRANES FOR RECOGNIZING AND TRANSPORTING SODIUM

A kind of self-organized hybrid material—3-(ureidophenol)propyltriethoxysilane was obtained from 3-isocyanatopropyltriethoxysilane and aminophenol with chloroform as solvent.The structure and the morphology of the materials were characterized by FTIR,DSC,and XRD methods.The ion channel membrane was obtained by two ways,one of them is to prepare membranes by coating the sol onto commercial ultrafiltration planar polyacrylonitrile supports,and the second is to prepare blend membranes by casting on glass sheets the solution of the hybrid material and polyacrylonitrile(PAN).The chemical structure and surface morphology of the membranes were characterized by ATR-FTIR and SEM separately.The ion transport property of the membrane was tested by our self-made device.The results showed that the surface of ion channel membranes was dense and the dense layer was about 8 ～ 10 μm thick for membranes prepared by both methods.There is obvious difference in the transport rate of ions for the two kinds of membranes.The transport rate of the membrane made by blending method is lower than that by coating method.The transport mechanism of these ion channel membranes was explained by molecular self-organization through the hydrogen bonding action.What's more,the ion channel membranes possess the function of recognizing and transporting sodium ions.