Common solvents and reagents were purchased from commercial suppliers (VWR, Acros, Sigma-Aldrich, Fluka, Fluorochem) at ≥95 % quality and used as received. Extra dry tetrahydrofuran (THF) and dimethylformamide (DMF) (over molecular sieve) were used as supplied. Triethylamine (TEA), (VWR, technical purity) was distilled under N 2 from KOH before use. The water used in all syntheses and in particle tracking experiments was taken from a Thermo Fisher GenPure Pro instrument with a resistivity ≥ 18M Ω • cm.