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Self-assembly Mechanism (self-assembly + mechanism)
Selected AbstractsNucleation-Governed Reversible Self-Assembly of an Organic Semiconductor at Surfaces: Long-Range Mass Transport Forming Giant Functional Fibers,ADVANCED FUNCTIONAL MATERIALS, Issue 18 2007G. De, Luca Abstract The use of solvent-vapor annealing (SVA) to form millimeter-long crystalline fibers, having a sub-micrometer cross section, on various solid substrates is described. Thin films of a perylene-bis(dicarboximide) (PDI) derivative, with branched alkyl chains, prepared from solution exhibit hundreds of nanometer-sized PDI needles. Upon exposure to the vapors of a chosen solvent, tetrahydrofuran (THF), the needles re-organize into long fibers that have a remarkably high aspect ratio, exceeding 103. Time- and space-resolved mapping with optical microscopy allows the self-assembly mechanism to be unravelled; the mechanism is found to be a nucleation-governed growth, which complies with an Avrami-type of mechanism. SVA is found to lead to self-assembly featuring i),long-range order (up to the millimeter scale), ii),reversible characteristics, as demonstrated through a series of assembly and disassembly steps, obtained by cycling between THF and CHCl3 as solvents, iii),remarkably high mass transport because the PDI molecular motion is found to occur at least over hundreds of micrometers. Such a detailed understanding of the growth process is fundamental to control the formation of self-assembled architectures with pre-programmed structures and physical properties. The versatility of the SVA approach is proved by its successful application using different substrates and solvents. Kelvin probe force microscopy reveals that the highly regular and thermodynamically stable fibers of PDI obtained by SVA exhibit a greater electron-accepting character than the smaller needles of the drop-cast films. The giant fibers can be grown in,situ in the gap between microscopic electrodes supported on SiOx, paving the way towards the application of SVA in micro- and nanoelectronics. [source] Three-Dimensional Nanonetwork Assembled in a Photopolymerized Rod ArrayADVANCED MATERIALS, Issue 23 2003H.-B. Sun One- and two-photon interferential patterning of photopolymerizable resin is demonstrated to lead to well-defined two-dimensional (2D) photonic crystal structures (which beat the diffraction limit) and also 3D nanonetworks, such as that shown in the Figure. The fiber-like features are probably formed by a novel self-assembly mechanism during drying. Applications in photonics are foreseen. [source] Self-Assembly of Large Multimolecular Micelles from Hyperbranched Star CopolymersMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2007Haiyan Hong Abstract This work focused on the synthesis and aqueous self-assembly of a series of novel hyperbranched star copolymers with a hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] (HBPO) core and many linear poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) arms. The copolymers can synchronously form unimolecular micelles (around 10 nm) and large multimolecular micelles (around 100 nm) in water at room temperature. TEM measurements have provided direct evidence that the large micelles are a kind of multimicelle aggregates (MMAs) with the basic building units of unimolecular micelles. It is the first demonstration of the self-assembly mechanism for the large multimolecular micelles generated from the solution self-assembly of hyperbranched copolymers. [source] Self-Assembled Heteroepitaxial Oxide Nanocomposite Thin Film Structures: Designing Interface-Induced Functionality in Electronic MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Judith L. MacManus-Driscoll Abstract Achieving self-assembling/self-organizing systems is the holy grail of nanotechnology. Spontaneous organization is not unique to the physical sciences since nature has been producing such systems for millions of years. In biological systems global patterns emerge from numerous interactions among lower-level components of the system. The same is true for physical systems. In this review, the self-assembly mechanisms of oxide nanocomposite films, as well as the advantageous functionalities that arise from such ordered structures, are explored. [source] Polymer-Controlled Crystallization of Unique Mineral SuperstructuresADVANCED MATERIALS, Issue 4 2010Shao-Feng Chen Abstract The origin of complex superstructures of biomaterials in biological systems and the amazing self-assembly mechanisms of their emergence have attracted a great deal of attention recently. Mimicking nature, diverse kinds of hydrophilic polymers with different functionalities and organic insoluble matrices have been designed for the morphogenesis of inorganic crystals. In this Research News, emerging new strategies for morphogenesis and controlled crystal growth of minerals, that is, selective adsorption and mesoscale transformation for highly ordered superstructures, the combination of a synthetic hydrophilic polymer with an insoluble matrix, a substrate, or the air/solution interface, and controlled crystallization in a mixed solvent are highlighted. It is shown that these new strategies can be even further extended to morphogenesis and controlled crystallization of diverse inorganic or inorganic,organic hybrid materials with structural complexity, structural specialties, and improved functionalities. [source] Towards a multidisciplinary approach to structuring in reduced saturated fat-based systems , a reviewINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 4 2010Paul Wassell Summary Although many food products are essentially emulsions, interest in the structuring of oil-continuous emulsions (and in specific cases water-continuous emulsions) is intense, particularly to meet the continuing challenge of reducing the degree of saturates in food systems. Consequently, it is necessary to observe the effects of structurants and to examine their impacts on current food systems. This is especially the case where novel structuring materials are used to wholly or partially replace traditional structurants. A multidisciplinary approach is discussed encompassing traditional and novel mechanisms considered able to structure within low saturated fat-based systems and which in themselves could also have emulsification properties. The presence of interfacial compositions as in emulsions requires a crucial understanding of the interactions within these compositions for the creation of building blocks in oil or fat structuring. Where a co-surfactant structure may be used, together with novel structurants, for example, wax esters, phytosterols, it is necessary to understand how these may influence interfacial film thickness, strength and flexibility. Understanding how to measure mechanical visco-elastic properties of structurant interactions both in model and real time dynamic measurements will be necessary to account for diffusion, orientation and self-assembly mechanisms. This review discusses combining traditional techniques with novel structurant technology; developing and validating dynamic measurement techniques; and investigation of real systems as opposed to purely model systems. [source] | ||||||||||