Apreo s hivoc

The chemical structures of the KPMs were characterized by ATR-IR (Thermo Scientific Nicolet iS50, America) and X-ray photoelectron spectroscopy (XPS, XSAM800, Kratos Analytical, U.K.). For ATR–IR, the microspheres were completely dried and pressed into slices to obtain the FTIR spectra between 600 and 4000 cm⁻¹. For XPS, the microspheres were also dried and pressed into slices for testing. The microstructures of the KPMs were obtained by scanning cryo-electron microscopy (Apreo S HiVoc, Thermo Fisher Scientific (FEI)). To prepare the samples for cryo-SEM, the KPMs were coated with a liquid conductive adhesive and put into a box with liquid nitrogen. After 5 min, the KPMs were cut off and then observed. The thermal stability of the KPMs was characterized by thermogravimetric analysis (TGA, Mettlle Toledo, TGA/DSC 3+, Switzerland). The curves of derivative thermogravimetric (DTG) were derived from TGA data. The mechanical properties of the KPMs were investigated by a universal testing machine (SANS CMT4000, MTS). The water uptake ratio of KPMs was calculated according to the following formula (1) [18 (link)]: $\text{WUR }(\text{\%})=\frac{({\text{W}}_{\text{e}}-{\text{W}}_{\text{d}})}{{\text{W}}_{\text{d}}}\times 100\%$ where W_e is the weight of the wet beads and W_d is the weight of the dry beads. Three parallel samples were employed, and the results are expressed as the mean ± SD (n = 3).