Avance neo 300 mhz spectrometer

Methoxy poly(ethylene
glycol)-b-polyethyleneimine was abbreviated as mPEG-PEI
in this paper. mPEG-PEI was prepared according to the method previously
described in the literature.^{53 −55 (link)} In this work, the relative optimized
feed molar ratio of the mPEG and PEI was about 1:1. Briefly, PEI (336
mg) and mPEG-NHS (336 mg) were separately dissolved in 10 mL of N,N-dimethylformamide (DMF), and then mPEG-NHS
solution was added dropwise to the PEI solution and stirred at 50
°C. After 24 h, the reaction solution was dialyzed (MWCO 3.5
kDa) against distilled water for 2 days and finally lyophilized and
kept at 2–8 °C until used in the subsequent reaction.
The final product was a white solid that was characterized by ¹H NMR. The ¹H NMR spectrum of the mPEG-PEI was
obtained on a Bruker AVANCE NEO 300 MHz spectrometer using D₂O as the solvent.

For solid‐state NMR experiments a Bruker Avance Neo 300 MHz spectrometer with a 2.5 mm magic angle spinning (MAS) probe was used. The samples were packed in 2.5 mm zirconium oxide rotors with vespel caps in the glove box under argon atmosphere. Cross polarisation (CP) from ¹H was used for the ¹³C measurements. 45,000 scans were recorded with a recycling delay of 3 s at transmitter frequency of 75.47 MHz and a contact time of 3500 μs. 2D – heteronuclear correlation (HETCOR) sequences used 1000 scans times 256 increments and a contact pulse of 200 μs, according to TMS with external standard adamantane (δ_CH=29.5ppm) with a spinning frequency of 15 kHz.