基于线形聚丙烯酰胺聚合物溶液流变学行为的影响因素

Influencing Factors of Rheological Behavior Based on Linear Polyacrylamide Polymer Solution

通过溶液聚合合成了线形聚丙烯酰胺(LPA),分别在LPA水溶液中聚合N,N-二甲基丙烯酰胺(DMA)和N-羟乙基丙烯酰胺(HEA),合成了LPA/PDMA和LPA/PHEA准互穿聚合物网络。研究了LPA黏均分子量、剪切速率、温度等因素对上述准互穿聚合物网络流变学的影响。结果表明,LPA溶液的临界缠结浓度随着黏均分子量的增加而下降;LPA、LPA/PHEA和LPA/PDMA溶液均表现出明显的剪切变稀行为,LPA/PHEA和LPA/PDMA溶液黏度要显著小于对应黏均分子量的LPA溶液的黏度;聚合物溶液黏度均随温度的升高而下降,并且LPA/PHEA、LPA/PDMA溶液对温度更加敏感。黏弹性结果显示:当聚合物的质量浓度为0.025 g/mL时,基于中、高黏均分子量LPA的聚合物溶液以弹性为主,聚合物网络结构较稳定;基于低黏均分子量LPA的聚合物溶液则以黏性为主,聚合物网络结构不稳定,易被外力破坏。

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(Nhydroxyethyl acrylamide)(LPA/PHEA)quasi-interpenetrating polymer networks were synthesized by polymerizing N,Ndimethylacrylamide(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(Mη)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(ηsp)of LPA solution increases slowly withρ.Whenρis more thanρ*,ηsp increases rapidly withρ.Andρ*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.Theηof 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.