VII Encontro da SBPMat

- Outlines of symposia
- General Timetable
- Timetable of oral and poster presentations

Administration
Aptor
7encontro@sbpmat.org.br
(16) 3371-7698

Fernando Galembeck

Born in São Paulo (Brazil) in 1943, studied at the University of São Paulo (Chemistry B.Sc. 1964, Physical Chemistry Ph.D 1970). Post-doc at the Universities of Colorado and California (Davis, 1972-4) and fellow at the Unilever Research Port Sunlight Lab. Currently Professor of Chemistry at the Universidade Estadual de Campinas, chaired the Institute of Chemistry (1994-1998) and was the university Vice-Rector (1998-2002).
Research interests are in the areas of materials chemistry, polymers, colloids and nano-structured systems. Authored 228 papers and 19 patents; advised 30 Ph.D. and 35 M.Sc. students. Received many prizes for his research largely made in cooperation with different companies. For contributions to industrial technology and innovation received the most important prizes in Brazilian science and technology, from the Association of the Chemical Industry and from different government agencies.

A new model for dielectric charging and electrostatic adhesion
Universidade Estadual de Campinas, Campinas, SP, Brazil

Electrostatic charging is widely known but it remains poorly understood, largely due to the lack of widely accepted mechanisms for charge acquisition and dissipation and this is largely related to the lack of consensus on the intervening species, electrons or ions.[1] This has important practical consequences because it makes the prevention of damaging electrostatic discharges rather empirical. It is also important for nanofabrication since electrostatic forces may largely exceed inertial forces for very small particles.
Early work from this laboratory revealed that insulator surfaces contain complex and stable patterns of nano-sized domains that were revealed by using scanning Kelvin probe microscopy, scanning electric potential microscopy (SEPM) or electric force microscopy (EFM).[2] More recently, carriers of excess charges in polymer lattices were identified as ions trapped during emulsion polymerization, by using analytical transmission electron microscopy associated to electron energy-loss spectroscopy (ESI-TEM). However, charge carriers in important insulators that are easily charged such as polyethylene and other thermoplastics, rubbers, cellulose and silicate glass were not identified by using these techniques.
Progress along this line was obtained during work on calibration of SEPM instruments that yielded two results: a procedure for electrostatic patterning of sub-micrometer domains on silica surfaces and the verification of its dependence on the atmosphere relative humidity (RH).[3] This led to a new model for the electrification of insulators, according to which charge bearing species are largely dissociated water ions or ion clusters that are deposited on the solid surfaces or removed from these, coupled to water vapor adsorption-desorption events. Charge transfer in dielectrics is thus coupled to mass transfer across the solid-gas interface and its rate depends largely on the atmosphere relative humidity that also contributes to surface conductance. This new model for the formation and dissipation of electrified domains has already been applied to many situations, especially to explain results on the electrostatic charging of paper and polyethylene. In another context, the identification of the presence of ions in dielectrics also led to a new model for electrostatic adhesion [4] in nanostructured materials,6 that accounted for the remarkable but previously unexpected adhesion between hydrophilic clay and hydrophobic latex particles, that produces new and unmatched mechanical and swelling properties in polymer-clay nanocomposites.
Work supported by CNPq, Fapesp and IMMC (Instituto do Milênio de Materiais Complexos).
References:
[1] Schein,L.B. Science, 2007, 316, 1572-1573.
[2] Galembeck, A.; Costa, C.A.R.; Silva, M.C.V.M.; Souza, E.F.; Galembeck, F. Polymer,
2001, 42, 4845-4851.
[3] Valadares, L.; Linares, E.; Bragança, F.C; Galembeck, F. J. Phys. Chem. C (in the press).
[4] Bragança, F.C.; Valadares, L.F.; Leite, C.A.P.; Galembeck, F., Chemistry of Materials,
2007, 19, 3334-3342.
fernagal@iqm.unicamp.br
Universidade Estadual de Campinas, Institute of Chemistry, CP 6154 Campinas SP, Brazil
13083-970