1. a Department of Plastics Engineering , University of Massachusetts Lowell , Lowell , Massachusetts , USA
2. d U.S. Army RDECOM , Natick , Massachusetts , USA
3. b Department of Chemistry , University of Massachusetts Lowell , Lowell , Massachusetts , USA
4. c Department of Physics, Center for Advanced Materials , University of Massachusetts Lowell , 265 Riverside St., Lowell , Massachusetts , 01854 , USA