Aerogels with 3D Ordered Nanofiber Skeletons of Liquid‐Crystalline Nanocellulose Derivatives as Tough and Transparent Insulators

Abstract

Aerogels of high porosity and with a large internal surface area exhibit outstanding performances as thermal, acoustic, or electrical insulators. However, most aerogels are mechanically brittle and optically opaque, and the structural and physical properties of aerogels strongly depend on their densities. The unfavorable characteristics of aerogels are intrinsic to their skeletal structures consisting of randomly interconnected spherical nanoparticles. A structurally new type of aerogel with a three-dimensionally ordered nanofiber skeleton of liquid-crystalline nanocellulose (LC-NCell) is now reported. This LC-NCell material is composed of mechanically strong, surface-carboxylated cellulose nanofibers dispersed in a nematic LC order. The LC-NCell aerogels are transparent and combine mechanical toughness and good insulation properties. These properties of the LC-NCell aerogels could also be readily controlled.

Surface properties and porosity of highly porous, nanostructured cellulose II particles

“…The distinct properties of nanocelluloses open a wide field of applications in composites (Cai et al 2012;Li et al 2014), insulation (Hayase et al 2014;Kobayashi et al 2014), packaging (Aulin et al 2010;Lavoine et al 2014), tissue engineering (Domingues et al 2014;Markstedt et al 2015) and many other utilization ways (Habibi et al 2010;Lin et al 2012). Nevertheless, drying of nanocelluloses with retention of their unique properties, in particular the high surface areas, remains a difficult and important challenge.…”

Mechanically robust aerogels derived from an amine-bridged silsesquioxane precursor

“…Commonly, it is accepted that a linear shrinkage of 10-15 %, which is about 27-39 % in volume shrinkage, is inevitable in supercritically dried aerogels [41]. In this study, the volume shrinkage of aerogels prepared using base catalysis and two-step acid/base catalysis is beyond the range.…”

Green Foams/Aerogels Based on Nanocellulose derived from Natural Plant Fibers

“…[6] To prepare homogeneous nanocellulose colloids, Isogai et al disintegrated never-dried native celluloses after oxidation mediated by the TEMPO followed by a homogenizing mechanical treatment, resulting in individualized, high aspect ratio and slender nanocellulose (Figure 2e). [7,8] Figure 3 (a-e) The cell structures and compressive stress-strain curves of nanocellulose-reinforced amylopectin foams, [9] (f) Digital photo and SEM image of TEMPO-oxidized nanocellulose aerogel, [10] (g) Functionalization of nanocellulose aerogels using conjugated polymers, [11] (h) ) Optical micrographs of LbL-functionalized nanocellulose aerogels in the dry state, and the corresponding chemical formulas of the functional polyanion used in the LbL. [12] Foams/Aerogels based on nanocellulose Utilizing nanocellulose as reinforcing fillers or building blocks, green foams/aerogels with advantageous mechanical properties can be produced (Figure 3).…”

“…[12] Foams/Aerogels based on nanocellulose Utilizing nanocellulose as reinforcing fillers or building blocks, green foams/aerogels with advantageous mechanical properties can be produced (Figure 3). [9][10][11][12] Svagan et al prepared foams using wood nanocellulose reinforced amylopectin-rich potato starch. [9] First, water suspensions were prepared from dissolved starch mixed with nanocellulose.…”

“…Kobayashi et al fabricated using TEMPO-oxidized nanocellulose as building blocks through acid-induced gelation and supercritical drying. [10] The aerogels are transparent and combine mechanical toughness and good insulation properties (Figure 3f). Pääkkö et al developed mechanically robust aerogels by freeze-drying of nanocellulose water suspensions.…”