3.2. Polymer Syntheses

The synthesis of 1-(3-aminopropyl)silatrane was performed using a modified protocol described in [32]: To a mixture of triethanolamine (15.0 mL, 16.8 g, 0.11 mol) with benzene (30 mL) was added a solution (27.3 g, 0.11 mol) of 1-(3-aminopropyl)triethoxysilane in benzene. (20 mL) and a catalytic amount (2 mg) of potassium tert-butanolate, the mixture obtained was heated to 80 °C and synthesis of silatrane was carried out for 10 h by azeotropic distillation of a mixture of benzene and ethanol while adding an equivalent amount of dry benzene to the reaction mixture. The reaction was controlled by the disappearance of hydroxy methylene proton signals in the NMR spectra of the reaction mixture. After the synthesis was completed, silatrane was not isolated but stored as a benzene stock solution of 0.544 g/mL.

¹H NMR (500 MHz, CDCl₃), δ: 0.24 (-Si-CH₂-), 1.38 (-CH₂-), 2.47 (H₂N-CH₂-), 2.68 (> N-CH₂-), 3.62 (-O-CH₂-).

Carboxyl-terminated polymers (1,3) were prepared by reaction of branched polymers with succinic anhydride, as shown on Scheme 1; Scheme 2:

In a typical procedure, 4.00 g (40 mmol) of succinic anhydride were dissolved in 75 mL of anhydrous THF in a 150 mL flask at 40 °C under vigorous stirring. Succinic anhydride being completely dissolved, the mixture of a branched polymer (2.10 g Polyglycerol or 2.85 g Boltorn H40, 25 mmol hydroxyl groups) and 4.04 g (40 mmol) of triethylamine, dissolved in 50 mL of anhydrous DMSO, was slowly added into the flask and the final mixture was reacted for 4 h. The crude product formed was precipitated twice with cold diethyl ether and dialyzed against THF (Roth “ZelluTrans” membrane (Carl Roth GmbH + Co. KG, Karlsruhe, Germany), MWCO = 1000 Da) for 48 h.

Polymer 1 ¹H NMR (500 MHz, CDCl₃), δ: 0.85 (CH₃-), 1.35 (-CH₂-), 2.51–2.80 (-CH₂-COO-), 3.10–4.0 (-O-CH₂-, > CH-);

Polymer 2 ¹H NMR (500 MHz, CDCl₃), δ: 0.85 (CH₃-), 0.95–1.25 (-CH₃, -CH₂-), 2.50–2.86 (-CH₂-COO-), 3.95–4.25 (-CH₂-O-).

Organosilicon-terminated polymers (3,4) were prepared by sequential reaction of carboxyl-terminated polymers (1,2) with 1-(3-aminopropyl)silatrane and (aminomethyl)trimethylsilane, as shown on Scheme 3; Scheme 4.

In a typical procedure, 6.82 mL of stock silatrane solution was evaporated under reduced pressure, forming 3.71 g (15mmol) of dry 1-(3-aminopropyl)silatrane, which was instantly dissolved in 10 mL of THF. The carboxyl-containing polymer (5.00 g of Polymer 1 or 5.73 g of polymer 2 (25 mmol carboxyl groups)) was dissolved in 10 mL of THF, followed by adding a solution of 4.05 g (25 mmol) CDI in 10 mL of THF to it. The reaction was carried out at 40 °C for 30 min, after which solution of 1-(3-aminopropyl)silatrane in THF was slowly added to the reaction mix and reacted for 2 h; Finally, a solution of 1.03 g (10 mmol) of (aminomethyl)trimethylsilane in 10 mL of THF was slowly added to the reaction media and reacted for 2 more hours, after which THF was distilled and the polymer synthesized was purified by dialysis against THF (Roth “ZelluTrans” membrane, MWCO = 1000 Da) for 48 h.

The content of silatrane in the synthesized hybrid macromolecules was varied by changing the ratio of 1-(3-aminopropyl)silatrane to (aminomethyl)trimethylsilane.

Polymer 3 ¹H NMR (500 MHz, CDCl₃), δ: 0.13 (CH₃-Si), 0.85 (CH₃-), 0.90–1.04 (-CH₂--Si), 1.35 (-CH₂-), 1.92–2.14 (-CH₂-), 2.57–2.80 (-CH₂-COO-,-CH₂-NH-), 3.00–3.17 (-CH₂-NH-), 3.17–3.90(-O-CH₂-, > CH-,-CH₂-N <), 4.05–4.35 (-CH₂-O-Si);

Polymer 4 ¹H NMR (500 MHz, CDCl₃), δ: 0.13 (CH₃-Si), 0.85–1.25 (-CH₃, -CH₂-,-CH₂-Si), 1.92–2.14 (-CH₂-), 2.60–2.80 (-CH₂-COO-,-CH₂-NH-), 3.00–3.17 (-CH₂-NH-), 3.17–3.47(-CH₂-N <), 3.9–4.28 (-CH₂-COO-, -CH₂-O-Si).