Nuclear magnetic resonance

The synthetic structure of PUs were measured using nuclear magnetic resonance and Fourier transform infrared. ¹H-NMR spectra of PUs were measured using nuclear magnetic resonance (500 MHz, Bruker, Karlsruhe, Germany), with 5% (w/v) polymer solution in Chloroform-d. FT-IR spectra of PUs were measured using a Fourier transform infrared (Varian 640-IR, Varian, Sydney, Australia), and the spectrum ranged from 4000 to 700 cm⁻¹. The number average molecular weights (M_n), weight average molecular weights (M_w), and polydispersity index (PDI) of the PUs were measured by gel permeation chromatography (ACQUITY, Waters, Milford, CT, USA). The measurement conditions were measured using the standard sample polystyrene (M_{w =} 47,200, 129,000 and 264,000) and using the Tetrahydrofuran solution at a rate of 0.5 mL/min⁻¹. The thermal analysis was measured using a differential scanning calorimetry (Exstar 7020, SEIKO, Tokyo, Japan). The PU sample was sealed in an Al pan, cooled to −70 °C under a nitrogen atmosphere, and then heated to 300 °C at a rate of 10 °C min⁻¹ and measured. Contact angle equipment (Phoenix 300, Surface Electro Optics, Suwon, Republic of Korea) was used to measure the wettability of the polymer surface.