Micrometric-scale materials

Micrometric-scale materials generally display the same physical properties as those in bulk form however, nanometric-scale materials may exhibit physical properties that are distinctively unlike those of bulk. Materials in this size range possess remarkable specific properties deriving from the transition from atoms or molecules to bulk form that takes place in this size range. On the one hand, the interfaces in poly crystalline microstructured materials are considered as defects that influence the macroscopic properties. On the other hand, in poly crystalline nanostructured materials, the interface dominates and the bulk plays a totally different role. Numerous experimental studies have shown that, if a material s particle size is less than the critical size of about 10 nm, its bulk properties change noticeably. A particle of about 10 nm contains 10" -10 atoms, 1-5% of which are on the surface of the particle and contribute substantially to the material s physicochemical properties [30]. Ensembles of such nanostructures will be shown here to be important in electrochemical applications such as electrodes [8,9,12,13,31-38]. 

These results illustrate how extended supramolecular-polymolecular entities build up through molecular recognition directed polyassociation of complementary components. They also show that molecular chirality is transduced into supramolecular helicity, which is expressed at the level of the material on nanometric and micrometric scales, amounting to a sort of size amplification of chirality. 

Dynamic self-assembly of supramolecular systems prepared under thermodynamic control may in principle be connected to a kinetically controlled sol-gel process in order to extract and select the interpenetrated hybrid networks. Such dynamic convergence between supramolecular self-assembly and inorganic sol— gel processes, which synergistically communicate, leads to higher self-organized hybrid materials with increased micrometric scales. 

Taken together, the results in the two figures show that the material formed from the slag has an approximately constant Si/Ca ratio of 0.62, and ratios of Mg Ca and of Al/Ca that vary from point to point on a micrometre scale but which are related to each other by the equation shown in Fig. 9.2. This was interpreted (H49) as indicating mixtures in varying proportions of... 

For all these reasons, the guanine building blocks and the sol-gel chemistry were used as molecular precursor to conceive hybrid chiral materials at nanometric and micrometric scales. Our efforts involved the synthesis and the self-assembly of a guaninesiloxane monomer Gsi (Fig. 3) in the G-quartet and G-quadruplex supramolecular architectures (Fig. 6), which are fixed in a hybrid organic-inorganic material by using a sol-gel transcription process, followed by a second inorganic transcription in silica, by calcination. 

Our findings showed a new way to transcribe the supramolec-ular chirality of a dynamic supramolecular architecture the transfer of the supramolecular chirality of G-quadmplex at the nanometric and micrometric scale is reported, thereby creating nanosized hybrid structures or microsized inorganic superstructures, respectively. Moreover, we obtain chiral materials by using a starting achiral guaninesiloxane Gsi as precursor of achiral G-quartet and of chiral supramolecular G-quadruplex. Figures 7 and 8 represent the first pictures of the dynamic G-quadruplex transcribed at the nanometric level. 

The application of low-copper-loading materials in the food packaging area is also currently under evaluation. Furthermore, the improvement of a controlled release system could find applications in cases where an adjustable, controlled, and perhaps very low ion release via a suitable stabilising shell, could answer the need for oligo-element dispensing on the micrometre scale. 

In this particular field, it is noted that polymers are not used as stmctural materials, strictly speaking, but as a tool for formulation (polymer formulation as opposed to the formulation of polymers commonly used). They are found here ranging from the micrometric scale as a component of nanoparticles to the micelle, or even the macromolecule in the case of nonionic polymer surfactants for the stabilization of particles [HAM 11, TAD 01]. A self-association leads to particle sizes from 50 to 80 nm in water in the presence of poly(ethylene gfycol). Nanoparticles can also be obtained with associative polymers which spontaneously self-assemble [GRE 11]. 

The aim of these studies is to understand and control the electrical properties of surfaces on a micrometric scale, that might be extremely useful for the application of these materials in the field of liquid crystal display (LCD) technology. In fact, it is well known that the LC anchoring properties depend not only on the substrate morphology but also on its electrical properties [68]. The electric polarization in nematic and other non-polar liquid crystals has essentially three origins flexoelectricity [65], orderelectricity [66,67] (related to the gradient in the order parameter) and the polarization of the substrate... 

It has been known for a long time that the surface ordering of a nematic (or other non-polar) liquid crystal is influenced by the ferroelectric domains of the anchoring substrate. In a work by M. Glogarova at al. [69], it is shown how the properties of a liquid crystal cell can be modulated and stabilized using a ferroelectric material as an anchoring substrate. These results motivated us to consider that the EFM technique could be efficiently used to create surfaces with variable anchoring conditions on a micrometric scale. 

Neutron scattering is a very flexible technique, which allows to probe structures with sizes from the near atomic to the near micrometre scale. This made SANS a method of choice when the hierarchical structure of complex materials must be elucidated, especially in conjunction with other techniques such as WAXD, SAXS or light scattering. ... 

When the polymer material is used as a scaffold (e.g., polymer hydrogels), its mechanical properties become important because cells are known to respond to the stiffness of a substrate. Rheology is commonly used to characterise the mechanical properties of polymer hydrogels and can equally be used to characterise ERMs (Chen et al., 2002 Kim and Healy,2003 Sanborn et al., 2002 van Dijk et al., 2010). In addition, to measure viscoelasticity on a micrometre scale, microrheology can be used. This method is able to measure local inhomogeneities in the material and is therefore able to measure inside small samples and cells (Yang et al., 2010). 

The overall morphology of the wax copolymer aggregates at the micrometric scale was also investigated by optical and transmission electron microscopy as complementary techniques for the USANS investigations. The results obtained allowed the clarification of the self-assembled structures in solution of the crystalhne-amorphous random copolymers. This has led to a broader understanding of wax crystal modification and control in solution than previously available. As noted, SANS is the required technique to study these hydrocarbon mixtures since contrast is easily achieved via the judicious mixture of hydrogenated and deuterated materials. As detailed experimentation has shown [7-18], this experimental capacity is vital for a complete... 

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