Synthesis, structure, and properties of N-2-hydroxylpropyl-3-trimethylammonium-O-carboxymethyl chitosan derivatives

N-2-hydroxylpropyl-3-trimethylammonium-O-carboxymethyl chitosan (HTCMCh) was synthesized through homogeneous reaction. The effects of different reaction condition on the properties of HTCMCh were characterized by FTIR, NMR, SEM, TEM, DLS, XRD, TGA, and DSC. The results of FTIR spectra, ¹H NMR, and ¹³C NMR proved the successful synthesis of HTCMCh. The DS was dependent upon reaction time and pretreated pH of the starting material, independent of temperature and n_epoxy/n_-NH2. With increasing reaction time, the crystallinity of HTCMCh decreased, and the intermolecular interactions transformed from hydrogen bonding to strong electrostatic interactions, which enhanced HTCMCh thermal stability. SEM observations showed smooth cross section morphologies of HTCMCh films. With the increase in reaction time, the tensile strength significantly increased. The viscoelasticity transformed from viscous to elastic with aging time, confirming the formation of polyelectrolyte complexes. The optimum reaction conditions: reaction time of 2 h, an initial material pH of 9.47, n_epoxy/n_-NH2 of 2/1.