Preparation, stability and rheology of polyacrylamide/pristine layered double hydroxide nanocomposites

Novel polyacrylamide (PAM)/pristine layered double hydroxide (LDH) nanocomposites have been prepared by a facile solution dispersion procedure, and their stability and rheological properties have been studied. The pristine LDHs without any surface organo-modification (LDH_NO3), synthesized by co-precipitation procedure, are dramatically exfoliated and uniformly dispersed in formamide. Subsequently, PAM/LDH_NO3 nanocomposites are prepared by a convenient solution dispersion procedure, wherein the dispersion structure of LDH_NO3 in PAM was studied by X-ray diffraction, size distribution measurements and Tyndall effect. The nanocomposites exhibit excellent stabilities toward various environmental conditions such as heating, centrifugation and salt-tolerance. Moreover, in the whole process of drying and after the re-dissolution, the nanocomposites kept a uniform dispersion structure without any precipitation formation. Finally, the dynamic and steady rheological investigations were conducted. Nanoscale LDH_NO3 particles and layers were found to have drastic effects on the PAM solution rheological behaviour with an obvious gel-formation process at a low LDH content, and strong frequency dependence of viscosity at low frequencies.