Conventional nanoscale interactions

Oxidative catalysis over metal oxides yields mainly HC1 and C02. Catalysts such as V203 and Cr203 have been used with some success.49 50 In recent years, nanoscale MgO and CaO prepared by a modified aerogel/hypercritical drying procedure (abbreviated as AP-CaO) and AP-MgO, were found to be superior to conventionally prepared (henceforth denoted as CP) CP-CaO, CP-MgO, and commercial CaO/MgO catalysts for the dehydrochlorination of several toxic chlorinated substances.51 52 The interaction of 1-chlorobutane with nanocrystalline MgO at 200 to 350°C results in both stoichiometric and catalytic dehydrochlorination of 1-chlorobutane to isomers of butene and simultaneous topochemical conversion of MgO to MgCl2.53-55 The crystallite sizes in these nanoscale materials are of the order of nanometers ( 4 nm). These oxides are efficient due to the presence of high concentration of low coordinated sites, structural defects on their surface, and high-specific-surface area. 

In heterogeneous catalysis by metal, the activity and product-selectivity depend on the nature of metal particles (e.g., their size and morphology). Besides monometallic catalysts, the nanoscale preparation of bimetallic materials with controlled composition is attractive and crucial in industrial applications, since such materials show advanced performance in catalytic processes. Many reports suggest that the variation in the catalyst preparation method can yield highly dispersed metal/ alloy clusters and particles by the surface-mediated reactions [7-11]. The problem associated with conventional catalyst preparation is of reproducibility in the preparative process and activity of the catalyst materials. Moreover, the catalytic performances also depend on the chemical and spatial nature of the support due to the metal-support interaction and geometrical constraint at the interface of support and metal particles [7-9]. 

An advantage of the PNs is the strong interaction between the polymer matrix and the nanoadditives because of the nanoscale dispersion of the nanoadditives in the polymer matrix. As a result, the PNs exhibit unique properties that are not shared by their microscale counterparts—conventional polymeric composites.70 However, the PNs are not easy to obtain. Simple physical mixing of a polymer with nanoadditives does not result in a PN but rather one obtains a more conventional composite with poor mechanical and thermal properties because of phase separation and, hence, the poor physical interaction between the matrix polymer and the nanoadditives. 

Another remarkable feature of responsive polymeric systems is that interactions on the molecular scale (the stimulus of some sort) lead to macroscopically detectable changes that are finally employed for the function (e.g., directed delivery of drugs). As the molecular-scale interactions and macroscopic function are so intimately linked it is noteworthy that rather few studies have dealt with the nanoscopic level of these materials. This may be due to the fact that many conventional methods of physical polymer characterization may simply not be able to resolve the many different, often counteracting interactions [18, 49, 50]. In processes like a response of any kind, solvent-polymer, solvent-solvent, and polymer-polymer interactions all play a cmcial role. Better understanding of the structure and interactions on the nanoscale is not only of value in itself but it may also shed light on similar processes in biomacromolecules and may aid the design and control of responsive polymers with respect to their applications [8, 48, 49]. These applications can be counted to the above-mentioned societal need of health, as responsive polymers are hot candidates for, e.g., drug or nucleic acid delivery purposes. 

The chemical, physical and biological properties of materials at nanoscale have fundamental differences in their properties at the conventional level because of quantum mechanical interactions at the atomic scale [2], Nanotechnology brings multidisciplinary innovations in all areas of... 

Improvements in the properties and performance of fiber-reinforced polymer matrix materials from the addition of nano- and microscale particles have been reported in the literature [8], The availabiHty of different types of nanoparticles offered the possibiHty to tailor fiber/matrix interactions at a nanoscale level. Recently, it has been proven that nanoparticles homogeneously dispersed in a polymer matrix are able to play a beneficial role on the fiber/matrix interfacial adhesion in different types of structural composites [ 11 ], as it will be shown later. Hence, regarding structural properties, nanocomposites appear particularly appropriate as means of enhancing the mechanical properties of conventional composites rather than their use as nanocomposites by themselves, except in some particular cases. 

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