1. International Center for Complex Systems and Departamento de Física, Universidade Federal do Rio Grande do Norte, Natal, RN 59078-970, Brazil
2. Center for Polymer Studies, Boston University, USA
3. Departamento de Física, Universidade Federal do Rio Grande do Norte, Natal, RN 59078-970, Brazil
4. Surface du Verre et Interfaces, Unité Mixte de Recherche CNRS/Saint-Gobain, 39 Quai Lucien Lefranc, 93303 Aubervilliers cedex, France