Evolution of Dielectric Behavior of Regenerated Cellulose Film during Isothermal Dehydration Monitored in Real Time via Dielectric Spectroscopy.

Zhao Zhao,Du Du,Chen Chen

doi:10.3390/polym11111749

Abstract

The dielectric relaxation behavior of a regenerated cellulose (RC) film during isothermal dehydration was monitored in real time via dielectric spectroscopy, in order to investigate on one hand the influence of water on its dynamics and the variation of microstructure and phase composition during dehydration on the other. The progression of water loss is clearly revealed by the evolution of the dielectric relaxation behavior with drying time, which suggests two distinctly different drying stages separated by a striking transition period. The dielectric relaxation behavior at the first drying stage is found overwhelmingly dominated by ionic motion, and that at the second stage is basically a result of molecular dynamics. The mechanisms of these relaxations are proposed, through which the influence of water on the dynamics of the RC film and the variation of the microstructure and phase composition of the film at different hydration state are discussed in detail. An interesting finding is that highly ordered but noncrystalline arrangement of cellulose molecules exists, but it can be formed only when the film is in specific hydration state. This study demonstrates that dielectric spectroscopy is an effective tool in real-time monitoring kinetic process.

Highlights

Regenerated cellulose (RC) attracts tremendous attention in recent decades, because it is advantageous over native cellulose in many aspects, such as greater diversity in structure, morphology, and functionality, while still holds the green nature [1,2,3]
A representative dielectric behavior of the RC film at the first drying stage is displayed in Figure 1c, from which one can notice that the value of ε” surpasses that of ε0 already at frequencies around 106 Hz
By real-time monitoring an isothermal dehydration process of cellulose film regenerated by physical dissolution via dielectric spectroscopy, the evolution of the dielectric relaxation behavior of the film with drying time was studied

Summary

Introduction

Regenerated cellulose (RC) attracts tremendous attention in recent decades, because it is advantageous over native cellulose in many aspects, such as greater diversity in structure, morphology, and functionality, while still holds the green nature [1,2,3]. Chemical derivatization and physical dissolution, are generally used to prepare RC materials. The latter is way more environmentally friendly than the former, thanks to less consuming of chemicals and no involvement of chemical reactions [2]. Physical dissolution method generally involves a dissolution process followed by a regeneration process. Depending on the regeneration process, various forms (fibers, beads, gels, etc.) of RC materials can be fabricated. Among these forms, RC film is an important one, which has long been used as packaging materials and has great potential in preparation of advanced composite materials [1,2,3,4,5]

Objectives

Methods

Results

Conclusion