Supporting Information for: Facile Formation of Uniform Shell Crosslinked Nanoparticles with Built-in Functionalities from N-hydroxysuccinimide-activated Amphiphilic Block Copolymers** By Yali Li, Isamu Akiba, Simon Harrisson, and Karen L. Wooley* Figure S1. The SAXS profiles for micelles and SCKs prepared from PMA-b-P(NAS-co-NAM) with dodecyl trithiocarbonate chain-end (a and b) and 2-cyanoisopropyl moieties as chain-end (c and d), respectively. Open circle: Experimental result, Solid line: Numerical calculation for core-shell sphere. [*] Prof. K. L. Wooley and Y. Li Center for Materials Innovation, Department of Chemistry and Department of Radiology Washington University in Saint Louis One Brookings Drive, CB 1134, Saint Louis, MO 63130-4899 (USA) E-mail: klwooley@wustl.edu Prof. I. Akiba Department of Chemical Processes and Environments, Faculty of Environmental Engineering University of Kitakyushu 1-1 Hibikino, Wakamatsu, Kitakyshu 808-0135 (Japan) Dr. S. Harrisson CSIRO Molecular and Health Technologies Locked Bag 10, Clayton South MDC, VIC 3169 (Australia) [**] The authors thank Prof. S. E. Sakiyama-Elbert and Ms. N. Kohrt (Department of Biomedical Engineering) for their assistance with DLS and zeta potential measurements, Mr. G. M. Veith (Washington University Electron Microscopy Laboratory) for assistance with TEM, and Dr. Jeffrey L. Turner for schematic drawings of SCK nanoparticles. This material is based upon work supported by the National Heart Lung and Blood Institute of the National Institutes of Health as a Program of Excellence in Nanotechnology (HL080729). 1