3.2.2. PGS Characterization

The molecular weight of synthesized polymers was evaluated using a size exclusion chromatography (SEC) system having a Waters 1515 isocratic high-performance liquid chromatography (HPLC) pump and a four Waters Styragel column set (HR3-HR4-HR5- HR2) with a UV detector Waters 2487 Dual λ Absorbance Detector set at 230 nm, using a flow rate of 1 mL/min and 60 μL as the injection volume. The samples were prepared by dissolving 50 mg of polymer in 1 mL of anhydrous CH2Cl2 and filtering the solution through 0.45 μm filters. Given the relatively high loading, a check was performed using a lower concentration of polymer (5 mg/mL) to verify that no column overloading had occurred. Higher loadings were preferred as the UV signal of PGS was relatively weak. Molecular weight data are expressed in polystyrene (PS) equivalents. The calibration was built using 16 monodispersed PS standards, having a peak molecular weight ranging from 1,600,000 Da to 106 g/mol (i.e., ethylbenzene). For all analyses, 1,2-dichlorobenzene was used as an internal reference.

Molecular weight data of the synthesized PGS were detected as follows: (Mn)− = 3100 Da; (Mw)− = 12,000 Da; D = 3.98. All data are expressed as polystyrene equivalents.

Differential scanning calorimetry (DSC) analyses were conducted using a Mettler Toledo DSC1 on samples weighing from 5 to 10 mg each. Melting and crystallization temperatures were measured using the following temperature cycles: (1) heating from −50 ◦C to 150 ◦C at 10 ◦C/min; (2) cooling from 150 to −50 ◦C at 10 ◦C/min; (3) heating from −50 to 150 ◦C at 10 ◦C/min. The first two cycles were run to erase the thermal history of the samples. Glass transition temperature (Tg) and melting temperature (Tm) were determined during the second heating scan.

Thermal transition data of the synthesized PGS were detected as follows: Tg = −11.3 ◦C; Tm = 8.1 ◦C.

Fourier transform infrared spectroscopy (FT-IR) Using a FT-IR Spectrometer (Spectrum 100, PerkinElmer) with an attenuated total reflection (ATR) was used to register spectra for PGS samples. FT-IR spectrum of PGS is reported in the supporting information file.

1H and 13C NMR spectra for PGS sample were recorded using a Bruker Ultrashield 400 MHz. The chemical shifts are reported in ppm and referred to TMS as internal standards. All samples were prepared by dissolving 6–8 mg of polymer into 1 mL of DMSO d6. Spectra are shown in the supporting information file.
