CONTEXT

Native cellulose occurs in the form of microcrystals and/or of very elongated microfibrils, often organized as fibres. This cellulose can be found in plants, but also in certain fungi, bacteria, amoebae and even some marine animals.

Acid hydrolysis of cellulose in an aqueous medium leads to stable aqueous colloidal suspensions of individual microcrystals. Depending on the origin of the cellulose, the lateral dimensions of the microcrystals and/or microfibrils can vary from 2 nm to 50 nm. The lengths of the said microcrystals and/or microfibrils can greatly exceed one micron. Depending on the origin of the cellulose (for example cotton) and the concentrations used (for example high concentrations, varying between 2 and 10% w/w), stable colloidal dispersions of cellulose in water are organized in the form of a liquid crystal of the cholesteric type  the spacing of which can vary from 80 to 10 mu m, depending on the operating conditions employed. All properties and applications of cellulose microcrystals and/or microfibrils are due to the very high form factor of these objects (i.e. the ratio of length to width is high, typically over 10), and to their good dispersion in the usage medium. However, until now it has only been possible to obtain dispersions of cellulose microfibrils and/or microcrystals in water or in very polar solvents (glycerol, ethylene glycol, DMSO etc.)