Assembly of Liquid Crystalline Cellulose Nanocrystals for Preparation of
Anisotropic Aerogels with Ordered Structures
Guang Chu1, Dan Qu2 Eyal
Zussman1* and Yan Xu2*
1 Faculty of Mechanical Engineering, Technion-Israel
Institute of Technology, Haifa 32000, Israel
2 State Key Laboratory of Inorganic Synthesis and
Preparative Chemistry, Jilin University, 2699 Qianjin Street, Changchun
130012, China
KEYWORDS: Freeze casting, Liquid crystal, Cellulose nanocrystal,
Anisotropic aerogel
ABSTRACT: Imparting aerogels with structural anisotropy endows these
porous materials with direction-dependent properties with promising
novel applicability in material science. However, facile fabrication of
such anisotropic aerogels under mild conditions still remains a major
challenge. Here, we report on the fabrication of anisotropic aerogels
from chiral nematic ordered cellulose nanocrystals (CNCs) by a
directional freeze-casting process. The resulting CNCs aerogels were
millimetre-sized with lamellar mesostructural features and optical
anisotropy, exhibiting hierarchical structures perpendicular to the
direction of freezing. We show that the birefringence of CNC aerogels
arose from the
of liquid crystalline CNCs suspensions, rather than from the shape of
rod-like nanoparticles. Moreover, the versatility of the directional
freezing approach was expanded to a CNC-silica system, resulting in
anisotropic silica aerogels with an ordered mesopore-imprinted structure
template by the liquid crystalline-ordered CNCs. The highly directional
alignment, optical anisotropy, hierarchical porosity and large internal
surface area of CNC-based aerogels exhibit bear considerable potential
for future fire-resistant, direction-dependent mechanical and electrical
insulator applications.