1. Instituto de Ciencia y Tecnología de Polímeros (CSIC), C/Juan de la Cierva 3, 28006 Madrid, Spain
2. Department of Mechanics of Solids, Surfaces & Systems (MS3), Chair of Elastomer Technology & Engineering, Faculty of Engineering Technology, University of Twente, 7500 AE Enschede, The Netherlands
3. Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, 15121 Alessandria, Italy
4. Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid, Spain