1. Department of Physics and Fribourg Centre for Nanomaterials, University of Fribourg, Ch. Du Musée 3, CH-1700 Fribourg, Switzerland
2. Laboratory for Polymer Chemistry, Swiss Federal Institute of Technology, Department of Materials, ETH-Zurich, HCI J541, CH-8093 Zurich, Switzerland
3. Food and Soft Materials Science, Institute of Food, Nutrition and Health, ETH Zurich, CH-8092 Zurich, Switzerland
4. Helsinki University of Technology, Physics Laboratory, Helsinki 02015, Finland