Preparation of Self-supporting Bagasse Cellulose Nanofibrils Hydrogels Induced by Zinc Ions.

Peng Lu,Xin Liu,Ren Liu,Min Wu

doi:10.3390/nano8100800

Abstract

Cellulose hydrogels are often prepared from native cellulose through a direct cellulose dissolution approach that often involves tedious process and solvent recovery problems. A self-supporting cellulose hydrogel was prepared by gelation of the TEMPO-oxidized bagasse cellulose nanofibrils (CNF) triggered by strong crosslinking between carboxylate groups and Zn2+. TEMPO process was used to generate negatively charged carboxylate groups on CNF surface to provide a high binding capability to Zn2+. Three TEMPO-oxidized CNFs of different carboxylate contents were prepared and characterized. TEM and AFM microscopes suggested that the sizes of CNFs were fined down and carboxylated cellulose nanofibrils (TOCNFs) of 5–10 nm wide, 200–500 nm long, and carboxylate contents 0.73–1.29 mmol/g were obtained. The final structures and compressive strength of hydrogels were primarily influenced by interfibril Zn2+-carboxylate interactions, following the order of TOCNFs concentration > content of carboxylate groups > concentration of zinc ions. A CO2 sensitive self-supporting cellulose hydrogel was developed as a colorimetric indicator of food spoilage for intelligent food packaging applications.

Highlights

Cellulose nanofibrils (CNFs) are novel nanomaterials prepared from natural cellulose fibers
Significant depolymerization is inevitable during the TEMPO/NaBr/NaClO oxidation of celluloses, and this depolymerization probably resulted in the downsizing of the CNFs both in width and length [26]
The results presented above suggest that the mechanical strength of the CNFs hydrogel is adjustable by controlling concentrations of zinc ions and TOCNFs in dispersion systems, as well as the content of carboxylate groups on TOCNFs, and present an interesting way of tailoring CNFs hydrogel for specific applications

Summary

Introduction

Cellulose nanofibrils (CNFs) are novel nanomaterials prepared from natural cellulose fibers. CNFs are of great interest for various applications relevant to the fields of material science and biomedical engineering due to its excellent mechanical properties, good biocompatibility, and tailorable surface chemistry [2]. Structured hydrogel materials derived from cellulose are of increasing interest for biomedical, cosmetic, and other applications where biocompatibility and biodegradability are required [6,7,8,9]. Cellulose has many hydroxyl groups that can form hydrogen bonding linked networks, forming hydrogels with fascinating structures and properties [10]. Cellulose hydrogels are generally prepared from native cellulose through direct cellulose dissolution, using solvents such as N-methylmorpholine-N-oxide (NMMO), ionic liquids (ILs), and alkali/urea aqueous systems [6,11]. Cellulose dissolution approaches often require multiple processing steps and involve solvent recovery problems

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