Molecular dynamics of poly(vinyl alcohol)/cellulose nanofibrils nanocomposites highlighted by dielectric relaxation spectroscopy

The main focus of this work is the investigation of dielectric properties of nanocomposites based on poly(vinyl alcohol) (PVA) matrix and cellulose nanofibrils (CNFs) reinforcement. Nanocomposites films with different CNFs content were prepared by simple mixing of PVA solution and CNFs suspension in water and water evaporation. Dielectric spectroscopy of the nanocomposite's films over a large temperature domain between similar to 50 degrees C to 170 degrees C and a frequency range of 0.1 Hz to 1 MHz was studied to probe the molecular mobility and interfacial transition of the material. In addition, differential scanning calorimetry (DSC) and spectroscopic analysis by FTIR and Raman were performed to further evidence interaction between CNFs and PVA matrix. Different relaxations were detected, namely 13 and a relaxations, water polarization and interfacial polarization known as Maxwell-Wagner-Sillars polarization (MWS), with magnitude and position being dependent on the CNF content.