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Complex fluids: liquid crystals, magnetic colloids, fluids of biological interest and elastomers


The investigation of the properties of non conventional fluids, which belong to area of "soft matter physics", is one of the modern branches of condensed matter. It has shown growing interest and activity in more recent years, with a wealth of relevant results, both from the fundamental and from the applied points of view, for an enormous host of new materials (liquid crystals and surfactant mixtures, colloids, emulsions and complex fluids in general, foams, polymeric solutions, granular materials, and many other similar systems). The investigation of these systems, on the basis of interdisciplinary methods and experimental techniques of condensed matter physics, using recent developments of statistical physics, and new and more powerful computational resources, has led to a deeper comprehension of the fundamental mechanisms of many-body interactions, and to the proposal and design of new devices, which are more and more present in our everyday life. This thematic project of research of the Complex Fluids Group of the IFUSP, for a period of four years, is composed by 5 sub-projects, integrated in the subject of research of the complex and super molecular fluids: 1) study physical-chemical characterization and ferro-hidrodynamics of ferrofluids; 2) study and physical-chemical characterization of Iyotropic and thermotropic crystals; 3) study and physical-chemical-biological characterization of fluids of biological interest. Particularly the components of the cholesterol (LDL, HDL and fractions); 4) thermo diffusion non-linear optics and magnetorheology of complex fluids; 5) study and physical-chemical characterization of elastomers. We objectify to keep some subjects of research (like that of the liquid crystals and ferrofluids) that are being developed in an adequate and productive way in our group, and to consolidate others that had been initiated recently (fluids of biological interest and elastomers). General objectives: 1) study of magnetic, structural and magneto-optical properties of magnetic fluids; study of the hydrodynamic instabilities in magnetic fluids; study of the wetting properties of complex fluids; study of the super paramagnetic particle rotational dynamics and its magnetic moments in ferrofluids; in vitro studies of biocompatible magnetic fluids; 2) attainment of experimental results to account for the behavior of micelle systems, its structural and dynamical aspects, under the action of external fields; use of new techniques for the treatment and analysis of these systems; study, from the fundamental point of view, and the exploitation of potential technological application of systems formed by molecules with the shape of "banana"; study of rheological properties of ferrofluids and liquid crystals; 3) in the case of fluids of biological interest, to understand better the role of the circulating lipids and the modified LDL in the context of the inflammatory diseases, as well as the effect of drugs in the treatment of metabolic problems. Investigate, mainly using the Z-Scan technique in the time scale of milliseconds (eventually in femtoseconds), the nonlinear optical response of the lipoproteins LDL, HDL and VLDL, in different experimental conditions. In addition, the optical response of these modified lipoproteins (oxidated with Fe or by means of the sonication) will be investigated; 4) investigate the properties of urea/urethane elastomers in different relative concentrations of the components, with and without the doping with nanometric magnetic particles. Different experimental techniques will be used in the attainment of the results: the radiocrystalography; different assemblies of linear optics for measurement of the birefringence and dicroism, in the presence of electric and magnetic fields; Z-Scan in time scales of fs and ms; setup to measure the ferroelectric polarization of liquid crystals; optical microscopy with polarized light; differential scanning calorimetry; electronic, atomic force and magnetic force microscopy; refractometry; among others. In terms of the relevance of the proposed subject, the project focuses on aspects which are in the frontiers of the Physics of the nano-structured materials, particularly the lyotropic and thermo tropic liquid crystals, the magnetic colloids, fluids of biological interest and elastomers. For the development of this project we have actually 1 student in a master thesis program, 3 students in PhD program and 3 researchers in post-doctoral program. Our subjects of research allow the incorporation of more post-doctors, students of PhD, master and under graduate students. Besides the members of the GFCx involved in the project, we have collaborators from Brazil (Institute of Chemistry of the USP, Institute of Biomedical Sciences of the USP, São Paulo School of Medicine of the UNIFESP, Faculty of Odontology of the UNESP of S. J. dos Campos), and from abroad (France, United States and Portugal). (AU)

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