Selective Isolation Methods for Cellulose and Chitin Nanocrystals

Abstract

This Minireview focuses on the selective isolation methods for the preparation of cellulose nanocrystals (CNCs) and chitin nanocrystals (ChNCs). Various selective preparation strategies with specific preparation conditions and reaction mechanisms are summarized. In particular, these selective reaction routes include controlled acid hydrolysis and selective oxidations at specific positions of cellulose or chitin fibers as well as particular reaction sites of the repeating monosaccharide building blocks of their main chains. These lead to selective cleavage of the ordered and non-ordered regions of cellulose and chitin and result in efficient production of CNCs and ChNCs. [ + ] These authors contributed equally to this work.

Thermal Stability of Cellulose Nanomaterials

“…It should be noted that all the reactions described so far have been carried out in an aqueous environment. Surface hydration is essential for the hydrolysis reactions to yield CNMs, as water favors accessibility to the surface hydroxyl groups and the generation of hydronium ions, responsible for the cleavage of the glycosidic bond and the progressive size reduction of cellulose fibers from micro- to nanoscale. , However, excessive water can be detrimental in some cases. , For example, CNMs with flame retardant surface groups tend to adsorb more water (higher hygroscopicity), which favors structural dehydration at low temperatures and charring rather than tar formation . Although effective in preventing oxidative reactions during the pyrolysis of materials, flame retardancy reduces the thermal stability of CNMs .…”

Valorization of Starch to Biobased Materials: A Review

“…The literatures available suggests various processing techniques such as acid hydrolysis [ 154 , 155 ] and ultrasonication [ 138 , 156 ]. Other methods such as mechanical treatment [ 155 ], ammonium persulfate (APS) oxidation [ 157 ], and 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO)-mediated oxidation [ 158 ] have also been proposed for the extraction of chitin.…”

Application of ionic liquids for the functional materialization of chitin

“…The preparation of nanoscale chitin assemblies, such as nanofibers and nanocrystals, is one of the most useful methods to practically transform chitin sources into functional materials because of the exceptional properties of bio-based nanomaterials, such as their lightweight, high tensile strength, low thermal expansion coefficient, biocompatibility, and nanosheet formability for sensing and electronic devices. [71][72][73][74][75][76] In addition to the conventional top-down approach, [77][78][79][80][81][82][83] regenerative bottom-up approaches from solutions/gels with ILs have also been used to fabricate chitin nanofibers (ChNFs). 24,33,[84][85][86] ChNF dispersions were obtained by immersing the aforementioned 9.1-10.7 wt% chitin ion gels with AMIMBr in methanol at room temperature for 24 h to slowly regenerate chitin, followed by sonication (Fig.…”