Experimental and theoretical study of dilute polyacrylamide solutions: effect of salt concentration.

The structure and intrinsic viscosity of the partially hydrolyzed polyacrylamide (HAPM) and polyacrylamide (PAM) in aqueous solution were investigated by comparative studies of molecular dynamics simulation over a wide range of the NaCl concentration. The radius of gyration (R(g)), the hydrodynamic radius (R(h)) and the ratio of the radius gyration and the hydrodynamic radius (ρ) were calculated for the PAM or HPAM in solutions with different NaCl concentrations at 298 K. The conformational changes of the polymer chain in different aqueous solution were discussed according to the molecular shapes. It was found that the change of the R(h) or the R(g) can reflect the change in the [η]. And the changes in the structure of the polymer chain with different NaCl concentrations were discussed via the ρ which can predict [η] changes. The results showed that behavior of the polymer solution calculated from the simulation agreed with the experimental measurements. Furthermore, the radial distribution functions for the HPAM solutions were investigated, which verified the micro-mechanism for the change of the structure. The results of this research showed that the computational method used in this work has practical applicability.