Chemically and mechanically isolated nanocellulose and their self-assembled structures

Area of Science:

• Materials Science
• Biotechnology
• Polymer Chemistry

Background:

• Cellulose nanomaterials (CNCs and CNFs) are derived from cellulose, a sustainable biopolymer.
• Various isolation methods yield nanocellulose with distinct properties.

Purpose of the Study:

• To isolate cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) from rice straw using different methods.
• To characterize the resulting nanocellulose materials.
• To investigate the self-assembly behavior of nanocellulose into crystalline fibers.

Main Methods:

• Isolation of CNCs and CNFs from rice straw cellulose via sulfuric acid hydrolysis, mechanical blending, and TEMPO-mediated oxidation.
• Characterization of nanocellulose properties including yield, crystallinity, dimensions, surface charge, and sulfate content.
• Analysis of nanocellulose self-assembly into fibers via rapid freezing and freeze-drying.

Main Results:

• Sulfuric acid hydrolysis yielded rod-like CNCs with high crystallinity (up to 90.7%) and negative surface charges.
• Mechanical defibrillation produced bimodally sized CNFs with 82.5% crystallinity.
• TEMPO oxidation resulted in the finest, most uniform CNFs but with lower crystallinity (64.4%).
• All nanocellulose types self-assembled into submicron fibers with high crystallinity (up to 90.9%) and cellulose Iβ structure.

Conclusions:

• Different isolation methods produce nanocellulose with tunable properties from rice straw.
• Nanocellulose self-assembly is influenced by dimensions, surface area, and surface chemistry.
• The self-assembled fibers exhibit high crystallinity, suitable for advanced material applications.