1. Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720, USA.
2. Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA.
3. Université Lyon, Université Lyon 1, CNRS, Ingénierie des Matériaux Polymères, UMR 5223, F-69003 Lyon, France.
4. Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433, USA.
5. Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
6. Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA.
7. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
8. Tsinghua-Berkeley Shenzhen Institute, University of California, Berkeley, Berkeley, CA 94720, USA.