Star polymer 5 was prepared as described earlier (see second step in Scheme 2b). Briefly, star polymer 4 (9 g, 0.9 mmol) was dissolved in 28 % aqueous ammonia solution (100 mL). The reaction mixture was left with stirring for 4 days at room temperature. The ammonia was allowed to evaporate over night after NaOH (5 M) was added dropwise until the pH reached 13. The solution was dialyzed several times against deionized water for 24 h. The aqueous solution was concentrated in vacuo and the water was completely removed by lyophilization to give 5 (7.2 g, 80%). H NMR (THF-d8, 40°C): δ 3.55 (s; c), 3.42 (br; b), 3.41 (s; d), 2.76 (br; a), 2.36 ppm (v br; NH2 and water from solvent), see also SI Figure .