Crystal structure of nanocellulose

Nanocellulose is a nano-scale material made of cellulose with a variety of crystal structures. Cellulose is essentially a linear polysaccharide polymer composed of glucose molecules connected through β-1,4-glycosidic bonds. The arrangement of cellulose crystals determines its crystal structure, mainly including the following types:

1. Cellulose I type (Cellulose I)

Features: Cellulose type I is the main crystal structure of natural cellulose and is present in plants, bacteria, algae and other organisms. Cellulose type I is further divided into two subtypes: cellulose Iα and cellulose Iβ.

Cellulose Iα: mainly exists in bacteria and algae, and its crystal structure is a triacrylic crystal system.

Cellulose Iβ: It is mainly found in higher plants and cotton, and its crystal structure is a monoclinic crystal system.

Molecular arrangement: Hydrogen bonds between molecular chains make cellulose type I crystals have high rigidity and strength.

2. Cellulose II

Features: Cellulose Type II is obtained by chemical treatment of cellulose Type I (such as alkali treatment) or regeneration processes (such as precipitation from solution). It is more stable than cellulose type I and is therefore more common in industrial applications.

Molecular arrangement: The molecular chains of cellulose type II crystals exhibit antiparallel arrangement, resulting in their differences in certain properties from cellulose type I, especially soluble and chemically reactive.

3. Cellulose III type (Cellulose III)

Features: Cellulose III type can be obtained by treating cellulose I or cellulose II with liquid ammonia (cellulose IIII) or ethylamine (cellulose IIII).

Molecular arrangement: Compared with cellulose type I and II, the crystal structure of cellulose type III is relatively loose and has a lower crystallinity.

4. Cellulose IV type (Cellulose IV)

Features: Cellulose type IV is obtained by heat treatment of cellulose type III. The structure of cellulose IV type is still not as stable as cellulose I and II and is therefore uncommon in nature.

Molecular arrangement: The molecular arrangement is significantly different from cellulose I and II, but the specific structure is relatively complex.

5. Cellulose V type (Cellulose V)

Features: Cellulose V-type is usually obtained by chemical treatment, such as treatment of cellulose type I or II with phosphate, and its structure has been rarely studied.

Summarize

Different crystal structures determine the physical and chemical properties of nanocellulose and their application in different fields. Due to its natural source and high strength, cellulose type I is the most widely studied and applied crystal form, while cellulose type II also occupies an important position in the industry due to its stability.