Effect of poly(vinyl alcohol) (PVA) concentration on rheological behaviors of TEMPO-mediated oxidized cellulose nanofiber/PVA suspensions

Abstract

2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidized cellulose nanofiber (TEMPO-CNF)/poly (vinyl alcohol) (PVA) suspension can be used to prepare composite. Therefore, understanding the viscoelastic property of TEMPO-CNF/PVA suspension is necessary. The analysis of the rheological dates from steady and dynamic rheology indicates that the suspension is pseudoplastic fluid with thixotropic behavior. When the concentration of PVA is in the dilute regime, the gel like behavior of the suspensions turns to liquid like state with the increasing frequency. Such behaviors are related to the entangled network among cellulose fibrils and the hydrogen bond interaction between TEMPO-CNFs and PVA. When the concentration of PVA is in semidilute and entangled regime, the suspensions show liquid character, because the viscosity of the suspensions are mainly determined by the entanglement of PVA molecules in homogeneous state. Furthermore, the TEMPO-CNF/PVA membranes were prepared by solution casting method. The Fourier transform infrared spectroscopy and atomic force microscope data proved the interaction between TEMPO-CNFs and PVA. This research reveals the importance of PVA concentration on the fluid characters of TEMPO-CNF/PVA suspensions, providing the approach to adjust the viscosity of TEMPO-CNF suspensions.