Aerogels are lightweight, porous materials that are useful in a variety of applications, including as insulators, electrodes for conversion and storage, oil sorbents, and catalysts. Aerogels are made from colloidal suspensions, whose particles are often randomly distributed in the sol. Therefore, rapid drying of a gel into an aerogel usually gives a disordered network. Introducing order into aerogels may result in materials with improved functionality.
Mark J. MacLachlan, University of British Columbia, Vancouver, Canada, and colleagues have discovered a simple way to produce ordered aerogels from liquid crystalline cellulose nanocrystals (CNCs). The team sealed a colloidal suspension of CNCs in water in a vial and waited two to four days until phase separation occurred and the CNCs had formed a liquid crystal. The water was then exchanged with alcohol to induce gelation and “freeze” the liquid crystalline form of the CNCs in place. After supercritical drying, a porous aerogel was obtained that retained the chiral nematic order of the original liquid crystalline phase.
The researchers further extended this concept to make CNC/silica and silica aerogels with a periodic chiral nematic order with surface areas of up to 725 m2/g. These aerogels can serve as potential templates for the synthesis of other porous, ordered aerogels and may have interesting applications for chiral separation or catalysis.
- Aerogel materials with periodic structures imprinted with cellulose nanocrystals,
Yi-Tao Xu, Yiling Dai, Thanh-Dinh Nguyen, Wadood Y. Hamad, Mark J. MacLachlan,