Gpc 515

Gel permeation chromatography (GPC 515, Waters, Milford, MA, USA) was used to determine number- and weight-average molar masses (M_n and M_w) and dispersity (Ð) of the synthesized copolymers. The analyses were carried out using a Waters 1515 gel permeation chromatograph equipped with HR 1, HR 3, and HR 4 columns, thus covering a molecular weight range of 100–500,000 g mol⁻¹. Tetrahydrofuran was used as the eluent at a flow rate of 1.0 mL min⁻¹, at 30 °C. A differential refractive index detector was used and average molar masses (M_n and M_w), as well as dispersity (Ð), were calculated from a calibration curve based on polystyrene (PS) standards from Polymer Laboratories.
Copolymer composition was determined using ¹H NMR (Varian Mercury 300 MHz, Varian, Santa Clara, CA, USA). Copolymer samples were dissolved in deuterated chloroform and scanned 32 times at room temperature.
Chemical structures of the copolymers and modified PLA were analyzed by Fourier transform infrared spectroscopy. The FTIR spectra of samples were measured at room temperature with 32 scans at a resolution of 1 cm⁻¹ using a Nicolet IZ10 spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) over the wavenumbers ranging from 4000 to 600 cm⁻¹.

The number average molecular weight (Mn) and weight average molecular weight (Mw) of the sol samples were characterized by gel permeation chromatography (GPC, 515, Waters, Milford, MA, USA). Tetrahydrofuran was used as the solvent at ambient temperature. The polystyrene standard samples with narrow-molecular weight distribution were used as reference.