Molecular dynamics simulations of the solubility of chitosan grafted polyacrylamide and its adsorption mechanism with kaolinite: Impact of length and distribution of branched‐chain

Abstract Graft modification can effectively improve the flocculation performance of chitosan. In this work, molecular dynamics simulations were employed to investigate the water solubility of chitosan‐grafted polyacrylamide (CTS‐g‐PAM) and its adsorption mechanism with kaolinite, focusing on the effects of branched‐chain length and distribution. The solubility parameters obtained from the simulations align better with those calculated using the group contribution method. The radius of gyration (Rg), solvation free energy (∆G SFE ), mean square displacement and diffusion coefficient were utilized to analyze changes in solubility of these CTS‐g‐PAM in aqueous solution. The adsorption interaction between CTS‐g‐PAM and kaolinite was investigated using interaction energy and diffusion coefficients. The water solubility of CTS‐g‐PAM initially increased, followed by a subsequent decrease as the length of branched‐chain increased along with a decrease in their number. Similarly, the adsorption interaction between CTS‐g‐PAM and kaolinite increased firstly followed by a decrease with increasing branched‐chain length. The magnitude of interaction energy with kaolinite (0 0 1) followed the order of CA10‐12 (−826.227 kcal/mol) >CA8‐15 (−744.583 kcal/mol) >CA6‐20 (−637.366 kcal/mol) >CA12‐10 (−598.109 kcal/mol). These trends align with the findings of flocculation tests. Our work provides a theoretical basis for designing chitosan‐based flocculants with enhanced water solubility and improved flocculation efficiency.