1. Department of Materials Engineering; Federal University of São Carlos; São Carlos Brazil
2. Institute of Macromolecules; Federal University of Rio de Janeiro; Rio de Janeiro Brazil
3. Division of Materials Processing and Characterization; National Institute of Technology; Rio de Janeiro Brazil
4. Positron Annihilation Spectroscopy Laboratory, Department of Chemistry; Federal University of Minas Gerais; Belo Horizonte Brazil
5. Polymer Laboratory, Department of Chemistry; Federal University of São Carlos; São Carlos São Paulo CEP 13565-905 Brazil