Nanostructured materials: liquid crystals and magnetic colloids

• Grant number: 02/08813-6
• Support Opportunities: Research Projects - Thematic Grants
• Start date: July 01, 2003
• End date: June 30, 2007
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Antonio Martins Figueiredo Neto
• Grantee: Antonio Martins Figueiredo Neto
• Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

This thematic project of research of the Group of Complex Fluids of the IFUSP, for a period of four years, has for general objectives: 1) structural and electric characterization of liquid crystals formed by molecules with the form of banana and doping of mesophases with organic solvent; 2) study of the mechanism of ratchets, or molecular engines, in ferrofluids doped liquid crystals with; 3) nonlinear optics of liquid crystal and ferrofluids in time scales of femto and milliseconds; 4) structural characterization of complex fluid, in particular lyotropic liquid crystals with and without the addition of ferrofluids and phase transitions; 5) measurement of the Soret coefficient of ferrofluids in different experimental conditions of the samples. Different experimental techniques will be used in the attainment of the results: the radiocristalography; different assemblies of linear optics for measurement of the birefringence and dicroism, also in the presence of electric and magnetic fields; Z-Scan in time scales of fs and ms; setups to measure the ferroelectric polarization of liquid crystal; setups to measure of the molecular tilt angle of liquid crystalline smectic structures; optic microscopy of polarized light. In terms of the relevance of the this proposal, the project focuses on aspects of the frontier of the Physics of the nanostructured materials, particularly the lyotropics and thermotropic liquid crystals and the magnetic colloids, as described in the foIlow: a. the molecules with anisometry of the twisted type (usually called banana) present an extremely rich topology of the phase diagram being, perhaps the only current example of chiral structures without basic unit with chiral carbons. The study of its electro-optical properties has relevance from the basic point of view, since there are similarities between its phases and those found in superconductors at high temperature, as also practical, being able to be revolutionary in the manufacturing of devices and displays. Another extremely interesting aspect of the scientific research with this type of molecule is the observed nano segregation when organic solvent is added to this mesophases. Nanoscopic devices as lamellar structures and filaments can be developed as products of this research; b. the mechanism of ratchet (or molecular engine) is one of the most fascinating subjects of the Physical-Chemical of complex fluids. It possesses interesting and intriguing biological implications... (AU)