Research of molecular dynamics simulations of polyacrylamide water solution

In order to simulate the polymer-containing sewage produced in the actual coal preparation process, the non-ionic polyacrylamide（NPAM） and the anionic polyacrylamide（HPAM）aqueous solution system are simulated by molecular dynamics method, and the COMPASS II force field is selected. By analyzing equilibrium conformation, curve of mean square displacement, radial distribution function, diffusion trajectory and mean square radius of gyration, the relationship between the properties of polymer solution and the microstructure of polyacrylamide（PAM） in aqueous solution are further explored. The results show that NPAM formed a sphere with the hydrophobic core, and is suspended in the solution, while HPAM aggregated at the bottom of the solution. The diffusion coefficient of water molecules in HPAM solution is larger than that in NPAM solution. HPAM surface has more interactions with nearby water molecules, and forms strong hydrogen bonds. The displacement and motion range of water molecules in HPAM solution are larger than that in NPAM. NPAM is stretched better than HPAM in water solution.