Dissipative particle dynamics simulation on the association properties of fluorocarbon-modified polyacrylamide copolymers

The hydrophobic association properties of a modified polyacrylamide (HMPAM) solution are attributed to the composition of the solution and environmental factors. In this study, the hydrophobic association of fluorocarbon-modified polyacrylamide aqueous solutions has been investigated on a mesoscopic level by considering the variation of root mean square (RMS) end-to-end distances using dissipative particle dynamics (DPD) simulations. The hydrophobic association depends on the hydrophobic behavior of the groups incorporated, the environmental temperature, the addition of salts and the shear. The embedded fluorocarbon units in the polyacrylamide chains are trifluoroethyl methacrylate, hexafluorobuyl methacrylate and dodecafluoroheptyl methacrylate, respectively, and the corresponding copolymers are expressed as P(AM-AANa-3F), P(AM-AANa-6F) and P(AM-AANa-12F). The modeling results show that P(AM-AANa-12F) has the strongest hydrophobic interactions among the three copolymers. The hydrophobic association of P(AM-AANa-12F) solutions in pure water is lower than that of corresponding salt-water solutions and shows stronger positive salinity sensitivity. P(AM-AANa-12F) can maintain its hydrophobic association in aqueous solution at high temperature, and its three-dimensional network can be reformed after shear. These conclusions are consistent with the experimental and theoretical results.