Ice-Templated Porous Nanocellulose-Based Materials: Current Progress and Opportunities for Materials Engineering

Abstract

Nanocelluloses (cellulose nanocrystals, CNCs, or cellulose nanofibrils, CNFs) are the elementary reinforcing constituents of plant cell walls. Because of their pronounced slenderness and outstanding intrinsic mechanical properties, nanocelluloses constitute promising building blocks for the design of future biobased high-performance materials such as nanocomposites, dense and transparent films, continuous filaments, and aerogels and foams. The research interest in nanocellulose-based aerogels and foams is recent but growing rapidly. These materials have great potential in many engineering fields, including construction, transportation, energy, and biomedical sectors. Among the various processing routes used to obtain these materials, ice-templating is one of the most regarded, owing to its simplicity and versatility and the wide variety of porous materials that this technique can provide. The focus of this review is to discuss the current state of the art and understanding of ice-templated porous nanocellulose-based materials. We provide a review of the main forming processes that use the principle of ice-templating to produce porous nanocellulose-based materials and discuss the effect of processing conditions and suspension formulation on the resulting microstructures of the materials.

Functional Materials from Nanocellulose: Utilizing Structure–Property Relationships in Bottom‐Up Fabrication

“…[ 130–132 ] Research interest into the use of nanocellulose in particular for developing such materials is growing rapidly, due in part to their tunable surface chemistries, stabilizing characteristics, and outstanding mechanical properties, in addition to possessing several of the other desirable features of foams and aerogels. [ 2,3,5,132–140 ] Typically, nanocellulose foams/aerogels are prepared from either a dispersion or hydrogel, which is subsequently dried via convective, super‐critical, or freezing‐based methods. [ 132 ] In this section, we focus on the intrinsic properties of nanocellulose allowing for the bottom‐up fabrication of structured monoliths with advanced functionality: the ability to stabilize interfaces/other nanoparticles, the ability to introduce structural anisotropy, and the ability to act as a template for other materials.…”

Antimicrobial Cellulose Nanofibril Porous Materials Obtained by Supercritical Impregnation of Thymol

“…For example, foam-like materials showing high porosity and high specific surface area have been prepared by freeze-drying or supercritical drying of nanocellulose suspensions. [21][22][23] Alternatively, dense structures such as films and nanopapers can be prepared by solvent casting or vacuum filtration. 24,25 The promising combination of essential oil with biopolymers in the wound healing process was discussed in the aforementioned article.…”

Structural packaging foams prepared by uni-directional freezing of paper sludge cellulose nanofibres and poly (vinyl alcohol)

“…The average porosity of the foams resulted in 97.9 ± 0.3 %. Unidirectional freezing allows the foam to exhibits a lamellar channel structure in the direction of freezing [11,20], this can be observed at a lower magnification in Fig.2c. At higher magnification (Fig 2d) the foam shows cellular pores with honeycomb-like structure with an average pore size of 3.2 ± 0.9 µm.…”

“…This entails a liquid nitrogen bath < -180 ℃ in an insulated polystyrene vessel, a copper rod used as a localised cold surface allowing the solution to freeze from the bottom up ( Fig.1). This freezing method influences the ice growth, pore formation and mechanical properties of the foam [11]. Fig.…”