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. 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-Nuclear Magnetic Resonance Spectra（¹H-NMR）, Fourier Transform Infrared Spectrometer（FT-IR）, and Differential Scanning Calorimetry（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 (M_η) 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 intrinsic viscosity molecular weight, shear rate, temperature, and other factors. When the mass concentration of polymer(ρ) is less than the critical entanglement concentration(ρ*), the specific viscosity(η_sp) of LPA solution increases slowly with ρ. When ρ is more than ρ*, η_sp increases rapidly with ρ. And ρ* of LPA solution decreases as molecular weight increases. LPA, LPA/PHEA, and LPA/PDMA solutions exhibit significant shear-thinning behavior, and the apparent viscosity(η) of LPA/PHEA and LPA/PDMA solutions is significantly lower than that of the corresponding LPA solution. The η 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 mass concentration of 0.025 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.