Molecular nanoreactors

Recent developments in polymer chemistry have allowed for the synthesis of a remarkable range of well-defined block copolymers with a high degree of molecular, compositional, and structural homogeneity. These developments are mainly due to the improvement of known polymerization techniques and their combination. Parallel advancements in characterization methods have been critical for the identification of optimum conditions for the synthesis of such materials. The availability of these well-defined block copolymers will facilitate studies in many fields of polymer physics and will provide the opportunity to better explore structure-property relationships which are of fundamental importance for hi-tech applications, such as high temperature separation membranes, drug delivery systems, photonics, multifunctional sensors, nanoreactors, nanopatterning, memory devices etc. 

The extensive studies carried out in the latter half of the 21st century on the selfassembling behaviour of low-molecular weight amphiphiles (natural or synthetic) have laid the foundation for their potential application in the field of nanotechnology. Although this potential is far from being yet fully explored, nanosciences and life-sciences already benefit by their utilization (e.g. liposomes, drug delivery, nanoreactors, etc.).278,279,280... 

The molecular size pore system of zeolites in which the catalytic reactions occur. Therefore, zeolite catalysts can be considered as a succession of nano or molecular reactors (their channels, cages or channel intersections). The consequence is that the rate, selectivity and stability of all zeolite catalysed reactions are affected by the shape and size of their nanoreactors and of their apertures. This effect has two main origins spatial constraints on the diffusion of reactant/ product molecules or on the formation of intermediates or transition states (shape selective catalysis14,51), reactant confinement with a positive effect on the rate of the reactions, especially of the bimolecular ones.16 x ... 

Larger capsules prepared by the same group have been used extensively as nanoreactors in which exotic chemical species can be formed. The group has also used a molecular panel approach as shown in Fig. 3.8. These compounds are, however, too small for any biomimetic activity. 

G. Tovar describes one of the novel chemical applications of modern colloidal systems by using such miniemulsions (in addition to classical suspension polymerization) for molecular imprinting. Here, the stable nanoreactor situation is used to synthesize particle surfaces with molecular sized cavities for biomedically relevant species or species to be separated from each other. Such receptor sites are nowadays preferentially made by the pathways of modern colloid chemistry. 

In the first chapter the synthesis and structures of new heteropolyoxoanions and related systems are discussed. Such systems can enclose nanoscopic spaces and can be regarded as nanoreactors . Clusters containing fragments of the lattices of semiconducting materials such as CdSe provide a vivid illustration of the transition from molecular-based to extended solid properties and show how the properties in the nanoscale region differ from those at each extreme. These are described in the second chapter. A third physical property for which a bounded system... 

Later, more sophisticated supramolecular complexes capable of improved molecular recognition started to be studied. New supramolecular approaches to constmct synthetic biohybrid catalysts were developed [190]. An example is the giant amphi-philes, formed by a (hydrophilic) enzyme headgroup and a synthetic apolar tail. These biohybrid amphiphilic compounds self-assemble in water to yield enzyme fibers and enzyme reaction vessels (nanoreactors [202]). 

Organized and constrained media may provide cavities and surfaces, sometimes called microreactors or nanoreactors,171 that can control the selectivity of photochemical reactions of reactants. There are many types of microreactors, for example, molecular aggregates of micelles or monolayers, macrocyclic host cavities of crown ethers or cyclodextrins and microporous solid cavities and/or surfaces of zeolites, silica or... 

From this structural model we can see that a loaded ferritin molecule is an organic/inorganic hybrid nanoparticle. Furthermore, the inorganic core represents a nano-sized portion of a solid-state structure and is thus of interest to researchers in the area of nanoscience where the properties of systems cannot be described using conventional ideas from molecular or from solid-state science. Also noteworthy is the control over the properties of the core which is exerted by the protein shell and which effectively provides a nanoreactor for the production of the iron(III) oxyhydroxide nanoparticle. Thus, the ferritin system provides insights into many aspects of nanoscience which are at the forefront of research in this field. Also, if we look back on how... 

Although the research field is still in its infancy, several examples of reactions, wherein self-assembled nanoreactors are applied and are shown to dramatic enhance or alter reactivity, have appeared, thereby demonstrating the power of the supramolecular concept. Detailed studies are required to fully understand the mechanisms behind the effects observed when carrying out reactions in nanoreactors. The results obtained so far sketch a bright prospective, as reactions have been observed that are unique to those carried out in capsules. In this review we have focussed on reactions that take place inside the capsules. However, molecular capsules have also been used to control reactions that take place outside the capsule for example by controlling the release of reagents, making the nanoreactor applications virtually unlimited. ... 

Thus, the stated above results have shown that for curing reaction proceeding in fractal space the reaction rate constant reduction is typical. The formation of a large number of microgels with smaller molecular weight in comparison with reaction in Euclidean space at the same conversion degree is also typical for such reaction. The dimensional border between nanoreactor and nanoparticle for the considered curing reaction has been obtained. 

The structure of such metallopolymers can be regulated by varying the ratio of sizes of block-copolymer (general molecular weight, composition) and micelle parameters (size of nucleus/cover, form, polydispersion), and this enables us to use block-copolymers as nanoreactors or templates. The ratio between the molecular weights of the first (polar) and the second (hydrocarbon) components Mi and M2) is important to provide steric stabilization M = nM2 (where n is the number of the second component chains). As a rule, M is 10 -10 andM2 = 10 -10. ... 

The current interest in the self-assembly of polymeric systems on surfaces stems from the many opportunities that these assemblies present for the preparation of novel functional nanomaterials, i.e., for drug delivery, in catalysis and nanoreactor technology, and for molecular templating. The interesting aspect of these systems is that their properties and structure can be manipulated by a number of parameters such as a) chemical structure, composition, and architecture, b) preparation methods and microengineering techniques used, and c) nature and properties of the underlying substrate and its interactions with the polymer chains [1-5]. 

Einally, the enormous number of possible combinations of oppositely charged polymeric components that can be involved in interpolyelectrolyte complexation offers attractive perspectives for the preparation of water-soluble multicompartment nanosized macromolecular co-assemblies with desired properties. We believe that such novel IPECs are very promising and will be in demand for their future applications in nanomedicine (e.g., gene and drug delivery, and diagnostic systems), biotechnology, and nanotechnology as nanocontainers, nanoreactors, and molecular templates for nanoelectronic devices. 

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