Influencing Factors of Rheological Behavior Based on Linear Polyacrylamide Polymer Solution

Linear polyacrylamide (LPA) was synthesized through an oxidation-reduction initiator system in aqueous solution, and Linear polyacrylamide/poly (N, N-dimethylacrylamide) (LPA/PDMA) and Linear polyacrylamide/poly (N-hydroxyethyl acrylamide) (LPA/PHEA) quasi-interpenetrating polymer networks were synthesized by polymerizing N, N-dimethylacrylamide (DMA) and N-hydroxyethyl acrylamide (HEA) in LPA aqueous solution, respectively. Characterization techniques, including ¹H NMR, FT-IR, and DSC, were employed to analyze the structures. The intrinsic viscosity of LPA, LPA/PDMA and LPA/PHEA were determined using a Ubbelohde viscometer, and the viscosity average molecular weight was calculated based on the intrinsic viscosity. The rheological properties of the above quasi-interpenetrating polymer networks were systematically investigated, focusing on the effects of LPA molecular weight, shear rate, temperature, and other factors. The rheological results show that before the critical entanglement concentration(c*), the specific viscosity(η_sp) of LPA solution increases slowly with increasing concentration. After the c*, the η_sp increases rapidly with concentration, and the c* of LPA solution decreases as molecular weight increase. LPA, LPA/PHEA, and LPA/PDMA solutions exhibit significant shear-thinning behavior, and the viscosity of LPA/PHEA and LPA/PDMA solutions is significantly lower than that of the corresponding LPA solution; the viscosity of polymer solutions decreases with increasing temperature, and LPA/PHEA and LPA/PDMA are more temperature-sensitive. The viscoelastic results show that in the linear viscoelastic region, at a concentration of 2.5% (g/mL), polymer solutions based on medium and high molecular weight LPA are predominantly elastic, indicating a relatively stable polymer network structure., while those based on low molecular weight LPA are predominantly viscous, indicating that the polymer network structure is unstable and easily disrupted by external forces.