3.3. Synthesis of PEtOx-A by CROP

Polymerizations yielding PEtOx-A in different lengths (DP10 and DP50) were carried out in a 1 L Normag reactor equipped with a KPG (Kerngezogenes Präzisions-Glasgerät) stirrer. The reactor was washed with 800 mL of boiling acetone for 1 h, dried at 115 °C under an argon stream for 1 h, evacuated, and filled with nitrogen thrice.

MeTos, EtOx, and acetonitrile were pumped into the reactor in that order. Afterward, the solution was refluxed, and the end of the polymerization was determined by ¹H NMR spectroscopy by taking 1 mL aliquots in regular intervals. After cooling to 40 °C, acrylic acid was first added, followed by triethylamine, and the mixture was stirred overnight at 50 °C. The reaction mixture was allowed to cool to room temperature, and a sample was analyzed by means of ¹H NMR spectroscopy. The crude product was then poured into a 2 L round bottom flask, leftover residue in the reactor were rinsed with 250 mL acetonitrile, and the solvent was removed under reduced pressure. After that, the crude product was dissolved in 1 L dichloromethane, washed thrice with a saturated NaHCO₃-solution and thrice with brine, and dried over Na₂SO₄/MgSO₄ (30/1). Subsequently, the product was filtered, and the solvent was removed under reduced pressure. The final product was dried in vacuo for an additional day to remove all the leftover solvent.

Weighing: MeTos (30.4 mL, 202 mmol), EtOx (204 mL, 2.02 mol), acetonitrile (270 mL), acrylic acid (20.7 mL, 303 mmol), and triethylamine (56 mL, 404 mmol). Yield: approximately 190 g (the final product was stored in CHCl₂ because of its hygroscopic properties).

¹H NMR (CDCl₃, 300 MHz): δ6.29 (br dd, J = 17.14, 3.20 Hz, 1H), 6.11–5.88 (m, 1H), 5.87–5.69 (m, 1H), 4.17 (s, 2H), 3.34 (br s, 37H), 2.91 (s, 3H), 2.38–2.11 (m, 20H), and 1.00 (br s, 30H). SEC (DMAc, 0.21% LiCl, RI detection, PS calibration): M_n = 2030 g mol⁻¹, Ð: 1.18.

PEtOx-A DP50: Weighing: MeTos (6.1 mL, 40.3 mmol), EtOx (204 mL, 2.02 mol), acetonitrile (294 mL), acrylic acid (4.15 mL, 60.5 mmol), and triethylamine (11.2 mL, 80.7 mmol). Yield: 184 g.

¹H NMR (CDCl₃, 300 MHz): δ6.33−6.20 (m, 1H), 6.04−5.91 (m, 1H), 5.82−5.68 (m, 1H), 4.15 (br s, 2H), 3.41–3.27 (br s, 200H), 2.94–2.87 (br s, 3H), 2.33−2.11 (m, 115H), and 0.98 (br s, 149H). SEC (DMAc, 0.21% LiCl, RI detection, and PS calibration): M_n = 7150 g mol⁻¹, Ð: 1.16.