Vnmr 500 mhz 11.7 tesla premium shielded nmr spectrometer

NMR scanning was performed using a Varian vnmr-500 MHz (11.7 Tesla) Premium Shielded NMR spectrometer (US) running Vnmrj software (the NMR Facility of the University of Michigan Chemistry Department, US) for 1 HNMR and 13 CNMR. NMR spectra are available in the Supporting Information.

Determination of dry glass transition temperature (dry T g )
Raw polymers (0.5-5 mg) were exactly weighed into aluminum pans with a lid and sealed. The dry T g was determined by a modulated differential scanning calorimetry method as previously described [17] (Discovery, TA instruments, US). A heat/cool/heat cycle was employed in which the temperature was ramped between -20°C and 90°C at 3°C/min, with a modulated amplitude of 1°C/min over 60 seconds.
Results were analyzed by the TRIOS software.
L/G ratio determination by nuclear magnetic resonance (NMR) spectroscopy
Each PLGA sample (~7 mg) was dissolved in deuterated chloroform (CDCl 3 ) (0.75 mL) and pipetted into a 5 mm × 7 in NMR tube (Aldrich® ColorSpec® NMR tubes, parameter 800 MHz frequency). NMR scanning was performed using a Varian vnmr-500 MHz (11.7 Tesla) Premium Shielded NMR spectrometer running Vnmrj software for 1 HNMR. Molar L/G ratios were determined by comparing proton intensities at chemical shifts 5.2 ppm (lactide, one proton) and 4.8 ppm (glycolide, two protons). The L/G molar ratio was converted to the L/G weight ratio. Signi cant differences were determined by comparing the changes in lactic content by subtracting the lactic content at day 0 from the lactic content determined at each timepoint.