Interaction study in homogeneous collagen/chondroitin sulfate blends by two-dimensional infrared spectroscopy

► NaCl was used to prepare neutral homogeneous Col/CS blends. ► The interactions between collagen and CS were studied by 2D FTIR correlation analysis. ► Only hydrogen bond existed in the blends as CS content was less than 50 wt%. ► The electrostatic interactions appeared as CS content was more than 50 wt%.