1.-Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Caracas, Venezuela, Profesor Asistente (Assistant Professor): September 1983-July 1985.
2.- Department of Physics, University of Bristol, Bristol, U.K., Research Assistant with a B.P. Venture Research Scholarship: August 1985-August 1989.
3.- Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Caracas, Venezuela, Profesor Agregado (Junior Associate Professor): September 1989-September 1991, Profesor Asociado (Associate Professor): October 1991-December 1996, Profesor Titular (equivalent to Full Professor in Venezuela): December 1996-September 2013. At USB, a promotion work has to be presented and examined by a committee before being promoted from one step to the next in the professorial scale.
From September 2013: EMERITUS PROFESSOR at USB
4.- Department of Chemistry, Johannes Guttenberg University, Mainz, Germany, Visiting Research Professor, invited by Prof. Reimund Stadler: February 1996-August 1996.
5.- Venture Business Laboratory, Hiroshima University. Visiting Research Professor, invited by Prof. Masamichi Hikosaka: February 1999-April 1999.
6. Since September 2013 he is an IKERBASQUE Research Professor at POLYMAT and at the Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country (UPV-EHU) in Donostia-San Sebastián, Spain.