Unity inova 400 nmr spectrometer

PEI (0.05 mmol, 1800 Da) was dissolved in 10 mL of methanol, and 0.8 mmol of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride was added. After stirring for 10 min, a solution of 0.8 mmol OA in 10 mL methanol was slowly added using a constant-pressure dropping funnel, and the reaction mixture was stirred at room temperature overnight under nitrogen. The mixture was then transferred to a dialysis bag with a molecular-weight cutoff (MWCO) of 3500 Da and dialyzed against a 1:1 water/methanol mixture for 24 h, then against purified water for another two days. The obtained oleic acid-modified polyethyleneimine (PEI-OA) material was ultimately freeze-dried, weighed, and stored at −20 °C. ¹H NMR spectra were recorded in dimethyl sulfoxide on a Varian UNITY INOVA400 NMR spectrometer (Palo Alto, CA, USA).

Mass spectra were obtained on a JEOL JMS-AX505WA mass spectrometer. NMR spectra were determined on a Varian UNITY INOVA 400 NMR spectrometer. Column chromatography was carried out over silica gel (40–60 μm, Merck, Kenilworth, NJ, USA). Fractions from column chromatography were monitored by thin layer chromatography (TLC) (silica gel 60 F₂₅₄ and RP-C₁₈ F_254S, Merck) under UV light or by heating after spraying 10% H₂SO₄ in CH₃OH (v/v).