1. Center for Polymers and Organic Solids Department of Chemistry and Biochemistry University of California Santa Barbara CA 93106 USA
2. Department of Mechanical Engineering Neuroscience Research Institute University of California Santa Barbara CA 93106 USA
3. Beijing National Laboratory for Molecular Sciences Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences Beijing 100190 P. R. China
4. Division of Chemistry Department of Physics Chemistry and Biology Linköping University Linköping SE ‐581 83 Sweden