Supporting Information An Apparent Size-Exclusion Quantification Limit Reveals a Molecular Weight Limit in the Synthesis of Externally Initiated Polythiophenes Michael Wong, Jon Hollinger, Lisa M. Kozycz, Theresa M. McCormick, Yijie Lu, Darcy C. Burns, and Dwight S. Seferos* Department of Chemistry, University of Toronto, Canada *Author to whom correspondence should be addressed. Tel: +01 (416) 946-0285; Fax: +01 (416) 946-7608; Email: dseferos@chem.utoronto.ca Contents Instrumentation and software .............................................................................................. 3 Materials ............................................................................................................................. 7 Synthesis of o-tolyl initiated poly(3-hexylthiophene)s ....................................................... 7 Figure S1. MALDI-TOF MS spectrum of P3HT-4 with proposed formulas. .................... 9 Figure S2. 31 P{ 1 H} NMR spectrum of cis-chloro(o-tolyl)1,3- bis(diphenylphosphino)propane nickel(II) in THF. .......................................................... 10 Figure S3. GPC chromatograms of o-tolyl initiated P3HTs at indicated catalyst loadings at 12 hour polymerization. ................................................................................................ 11 Figure S4. GPC chromatograms of o-tolyl initiated P3HT synthesized at 2% catalyst loading at indicated polymerization times. ....................................................................... 12 Figure S5. GPC chromatograms of o-tolyl initiated P3HTs at 2% catalyst loading synthesized at indicated concentrations. ........................................................................... 13 Figure S6. GPC chromatograms of P3HT-3 and P3HT-1. ............................................... 14 Figure S7. 500 MHz 1 H NMR spectrum of P3HT-4 in CDCl 3 at 25 °C. .......................... 15 Figure S8. 1 H NMR spectrum of P3HT-2c with 2.0 second delay time. .......................... 16 Figure S9. 1 H NMR spectrum of P3HT-2c with 5.0 second delay time. .......................... 17 Figure S10. 1 H NMR spectrum of P3HT-2c with 10.0 second delay time. ...................... 18 Figure S11. 1 H NMR spectrum of P3HT-1 with 2.0 second delay time. .......................... 19 Figure S12. 1 H NMR spectrum of P3HT-1 with 5.0 second delay time. .......................... 20 Figure S13. 1 H NMR spectrum of P3HT-1 with 10.0 second delay time. ........................ 21