Metastability of Nematic Gels Made of Aqueous Chitin Nanocrystal Dispersions

Abstract

Chitin nanocrystal aqueous dispersions were prepared by acid hydrolysis of crude chitin from crab shells. The resulting dispersions were studied with small deformation oscillatory experiments and polarized optical microscopy under different conditions of nanocrystal concentration, ionic strength, pH, and temperature. The chitin nanocrystal dispersions exhibited a nematic gel-like behavior with increasing solids concentration. The appearance of nematic-like structures could be explained by the Onsager theory for parallel alignment of anisotropic particles on entropic terms, while the sol-gel transition could be attributed to associative interactions between the chitin nanocrystals. With increasing ionic strength and pH, such associative interactions were enhanced, because the repulsive forces due to the electrostatic charges were reduced and, thus, stronger gels were formed. Heating of the nanocrystal dispersions led to further increases in the storage modulus (G'), which were irreversible upon cooling; the rate of G' increase (dG'/dt) was dependent on temperature.

Stabilizing oil-in-water emulsions with regenerated chitin nanofibers

“…At concentration of 1.00%, it became a self-supporting gel as evidenced by turning the test tube upside-down. These results suggested that the regenerated chitin might be used as a gelling material in a similar way to chitin nanocrystals (Tzoumaki, Moschakis, & Biliaderis, 2010).…”

Polymer organogelation with chitin and chitin nanocrystals

“…Chitin nanocrystals (ChN) were produced based on a protocol described by Tzoumaki et al 41 In the original protocol, the crude chitin was rst puried before use. However, EDX analysis (data not shown) showed that the provided crude chitin already had a purity of >98%, and therefore the purication steps were omitted.…”

“…Here, it can be clearly seen that the chitin aggregates have an average diameter of roughly 100 AE 50 mm. 41 Roughly 3.6 wt% of ChN is required to form a hydrogel. When present in sunower oil in the dilute regime (0.01 wt%), the average size was found to be around 70 mm, similar to the size found with cryo-SEM.…”

“…6b the organogels with ChN and PC. 41 Properties of the chitin organogels Rheological characteristics. Subsequently, these ordered and connected chitin strands interact to form a coarser network with large voids in which oil is entrapped (Fig.…”

11 Other polysaccharide nanocrystals

“…HCl 3 N 3⋅90 104 30 (Gopalan Nair and Dufresne 2003a;2003b;Gopalan Nair et al, 2003;Lu et al, 2004;Feng et al, 2009;Tzoumaki et al, 2010) 90 104 10 (Nge et al, 2003) 360 120 30 (Hariraksapitak and Supaphol, 2010) Riftia Tubes…”