Fig. 1

Characterization of PEG-PCL copolymer. a Proton nuclear magnetic resonance, b Thermogravimetric analysis of PEG-PCL copolymer spectra showing the diblock structure of copolymer. c The FTIR spectra of PEG-PCL copolymer, where the observed strong and sharp absorption band appearing at 1721 cm⁻¹ is characteristic of the stretching vibration of the ester carbonyl group (C=O) of PCL. The (C–H) stretching bands in PEG and PCL are vibrating at 2863 and 2942 cm⁻¹, respectively; d Thermal property of PEG-PCL diblock copolymer. The melting temperature of the copolymer was measured by differential scanning calorimetry (DSC) and a bimodal melting peak was observed at 54.8 °C