Self-assembly in solution

Nguyen-Misra M, Misra S, Wang Y, Rodrigues K and Mattioe W L 1997 Simulation of self-assembly in solution by triblook oopolymers with stioky blooks at their ends Prog. Colloid Polym. Sc/. 103 138-45... 

Finally, we have designed and synthesized a series of block copolymer surfactants for C02 applications. It was anticipated that these materials would self-assemble in a C02 continuous phase to form micelles with a C02-phobic core and a C02-philic corona. For example, fluorocarbon-hydrocarbon block copolymers of PFOA and PS were synthesized utilizing controlled free radical methods [104]. Small angle neutron scattering studies have demonstrated that block copolymers of this type do indeed self-assemble in solution to form multimolecular micelles [117]. Figure 5 depicts a schematic representation of the micelles formed by these amphiphilic diblock copolymers in C02. Another block copolymer which has proven useful in the stabilization of colloidal particles is the siloxane based stabilizer PS-fr-PDMS [118,119]. Chemical... 

Protein is an excellent natural nanomaterial for molecular machines. Protein-based molecular machines, often driven by an energy source such as ATP, are abundant in biology. Surfactant peptide molecules undergo self-assembly in solution to form a variety of supermolecular structures at the nanoscale such as micelles, vesicles, unilamellar membranes, and tubules (Maslov and Sneppen, 2002). These assemblies can be engineered to perform a broad spectrum of functions, including delivery systems for therapeutics and templates for nanoscale wires in the case of tubules, and to create and manipulate different structures from the same peptide for many different nanomaterials and nanoengineering applications. 

Hence, from the previously described light-scattering study of caseinate self-assembly in solution, we can postulate that heating/cooling not only alters the nature and strength of the physical (hydrophobic) interactions between emulsion droplets covered by caseinate. It most likely also transforms the nanoscale structural characteristics of the protein network in the bulk and at the interface, thereby affecting the viscoelastic and microstructural properties of the emulsions. 

As described in the Introduction, Pasteur showed beautifully that racemic molecules resolve spontaneously into chiral forms when they crystallize. We call them conglomerates, in which molecules form condensates comprised of only one enantiomer. The condensation into conglomerates can now be observed not only in crystals but in monolayers, fibers, and supramolecules self-assembled in solution [35]. The researches became possible because of the development of microscopic observation techniques at the nanometer scale. However, in crystals we still do not know what kinds of molecules show spontaneous resolution. Hence, observation of chiral resolution in soft matter may provide important information on the general question. 

Finally, we mention a remarkable example of lateral resolution reported for supramolecular nanostructures on hopg [96]. Held together by 72 hydrogen bonds, the molecular nanostructure is formed from three melamine-substituted calix[4]arene units and twelve 5,5-diethylbarbiturate molecules (Fig. 31a). The nanostructure, basically a stack of four rosettes, has chiral symmetry. With its components all being achiral, both enantiomers are formed upon self-assembly in solution. Deposition of the tetrarosettes on hopg leaves this nanostructure intact and allows surface self-assembly. AFM studies revealed close-packed 2D lattices formed by the tetrarosettes on hopg... 

Experimental evidence of hierarchical peptide self-assembly in solution... 

We used our experience with reversible encapsulation to arrive at a rule regarding the proper filling of space, the 55% solution [87]. The filling of space probably drives other recognition phenomena, even in those synthetic receptors that do not completely surround their targets [88]. Some of the earliest, finite self-assemblies in solution based on melamine/cyanuric acid recognition [89] had no other function than to fill space. However unconventional, the departure from mainstream physical organic chemistry [90] is familiar to us and may offer rewards. 

Fig. 9 Chemical system for mimicking an electrical extension cable. Structural formulas of the three molecular components 72+, 8-H+ and 92+ (a), which self-assemble in solution (CH2C12 room temperature) to give the 72+d8-H+d92+ triad (b). In the fully connected system, excitation with visible light of the Ru-based unit of 72+ is followed by electron transfer to 92+, with 8-H+ playing the role of an extension cable [58]...

In this chapter, the self-assembly of BCs is explored throughout the last examples of major contributions. The first part will be devoted to the self-assembly in solution as a way to prepare micellar nanoobjects with different shapes and behaviors. The second part will develop self-assembly in bulk and in thin films with a special paragraph dedicated to the guided assembly. 

Figure 33. Pictorial representation of the preparation of a surface-attached catenane by coupling self-assembly in solution with chemisorption onto a solid support [83].

Rasimas, J.P. Berglund, K.A. Blanchard, G.J. Measuring self assembly in solution incorporation and dynamics of a Tailor-made Impurity in precrystalfine glucose aggregates. J. Phys. Chem. 1996,100 (42), 17,034-17,040. 

A complete survey on calixarenes was far beyond the scope of this chapter. We therefore concentrated mainly on the chemistry, namely the synthesis and the (basic) chemical modification of calixarenes, which form the basis for aU fnrther stndies. Fnrther interesting aspects, such as inherent chirality of calixarenes, catalytic or biomimetic effects , larger structures formed via self-assembly in solution or in mono- and multilayers could be stressed only shortly. Important properties snch as complexation of cations , anions and of nentral gnests , including fnUerenes , conld not be treated at all. The same is tme for applications arising from these properties in snch different areas as sensor techniqnes , chromatographic separations or treatment of nuclear wastes . In all these cases, the reader is referred to special reviews. 

Deviations from OGM were recognized early on spectroscopic properties of molecular crystals Davydov shifts and splittings of absorption bands in molecular crystals are clear deviations from OGM and were rationalized based on the excitonic model (EM) [10, 14, 15, 16, 17]. This same model proved extremely successful to describe the complex and technologically relevant spectroscopy of molecular aggregates, i.e. of clusters of molecules that spontaneously self-assemble in solution or in condensed phases [IS]. Much as it occurs in molecular crystals, due to intermolecular electrostatic interactions the local bound electron-hole pair created upon photoexcitation travels in the lattice and the corresponding wave function describes an extended delocalized object called an exciton. We explicitly remark that the Frenkel picture of the exciton, as a bound electron-hole pair, both residing on the same molecule, survives, or better is the basis for the excitonic picture. The delocalization of the exciton refers to the fact that the relevant wave function describes a Frenkel exciton (a bound e-h pair) that travels in the lattice, and this is of course possible even when electrons and/or holes are, separately, totally localized. In other terms, the EM describes localized charges, but delocalized excitations. 

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