STRONG OR WEAK: WHO TAILORS THE MICROSTRUCTURAL PROPERTIES OF CELLULOSE AEROGEL BEADS?

Abstract

Cellulose aerogels are versatile materials having interconnected nanofibrillar network, low density and high porosity. They can be produced in different forms by shaping the solution to monoliths, sheets, beads and 3D printed complex structures. They can be effectively used for various applications when the physical properties can be tuned to adapt the demands. As these materials have meso- and macropores, tuning the pore volume can be done during gel network formation. Tailoring the properties of cellulose aerogel beads will be discussed in the presentation. Cellulose aerogel beads were commonly prepared by adding anti-solvents in the coagulation bath. Anti-solvents can generate the aggregated cellulose nano-network which leads to the formation of complete wet-gel body. One of the methods of gel structure formation can be developed by reversing the pH value, i.e., pH-induced gelation [1]. Cellulose can be dissolved in NaOH-water medium in the presence of additives such as urea [2]. The addition of acids in the coagulation bath can induce the gel-structure formation. We have been investigating the use of weak organic acids as coagulants to tailor the properties of cellulose aerogel beads [3]. Three weak acids, acetic acid, lactic acid, and citric acid, and a strong acid, hydrochloric acid, were chosen as coagulation baths. The production of aerogel beads by conventional dropping technique was studied and optimized for each acid. The produced cellulose aerogels were characterized by nitrogen adsorption-desorption isotherm, BJH pore data analyses, density analyses, IR spectroscopy, scanning electron microscopy, and X-ray powder diffractometry, and their properties were compared. In common, all the aerogel beads showed interconnected nanofibrillar network. The pore size distribution was highly influenced by the acids employed for regeneration. High concentration of weak acids contributed to low shrinkage, high specific surface area and high pore volume. In conclusion, this study showed an alternate path way to tailor the properties of cellulose aerogel beads.