Figure 4.

FT-IR spectra of (A) TQ, (B) mPEG5K-PCL10.3K, (C) mPEG5K-PCL18.5K, (D) F1-NS, (E) F2-NS, (F) F1-NC, and (G) F2-NC. TQ exhibited =C–H, C–H, and C=O stretching at 3050 cm⁻¹, 2970 cm⁻¹, and 1655 cm⁻¹, respectively. mPEG-PCL copolymers showed C–H stretching vibrations at 2950 and 2864 cm⁻¹ attributed to the ethylene oxide repeats, and a sharp C=O stretching band at 1730 cm⁻¹ corresponding to the carbonyl ester groups of PCL. The broad O–H stretching band appearing between 3700–3100 in the NC formulations (F) and (G) indicates the presence of hydrogen bonding interactions between the formulation components after adding castor oil.