pH-Responsive Properties of Asymmetric Nanopapers of Nanofibrillated Cellulose

A review on intelligence of cellulose based materials

Cellulose based materials are widely used in various fields such as papermaking, packaging, composite materials, textiles and clothing due to their diverse types, environmental friendliness, natural degradation, high specific strength, and low cost. The intelligence of cellulose based materials will further expand their application fields. This article first gives an in-depth analyzation on the intelligent structural design of these materials according to the two major categories of isotropic and anisotropic, then lists the main preparation methods of cellulose based intelligent materials. Subsequently, this article systematically summarizes the recent intelligent response methods and characteristics of cellulose based materials, and extensively elaborates on the intelligent application of these materials. Finally, the prospects for the intelligence of cellulose based materials are discussed.

Unraveling the control of reversibility for actuators based on cellulose nanofibers

In this work, we have prepared cellulose-based actuators taking advantage of the pH-sensitive solubility of chitosan (CH) and the mechanical strength of CNFs. Bilayer films were prepared by vacuum filtration inspired by plant structures that exhibit reversible deformation under pH changes. The presence of CH in one of the layers led to asymmetric swelling at low pH, thanks to the electrostatic repulsion between charged amino groups of CH, and the subsequent twisting with the CH layer on the outside. Reversibility was achieved by substituting pristine CNFs with carboxymethylated CNFs (CMCNFs), that are charged at high pH and thus competed with the effects of amino groups. Swelling and mechanical properties of layers under pH changes were studied by gravimetry and dynamic mechanical analysis (DMA) to quantify the contribution of chitosan and the modified CNFs on the reversibility control. This work evidenced the key role of surface charge and layer stiffness to achieve reversibility. Bending was triggered by the different water uptake of each layer, and shape recovery was achieved when the shrunk layer shower higher rigidity than the swollen layer.

Naturally Derived Janus Cellulose Nanomaterials: Anisotropic Cellulose Nanomaterial Building Blocks and Their Assembly into Asymmetric Structures

Naturally derived cellulose nanomaterials (CNMs) with desirable physicochemical properties have drawn tremendous attention for their versatile applications in a broad range of fields. More recently, Janus amphiphilic cellulose nanomaterial particles with asymmetric structures (i.e., reducing and nonreducing ends and crystalline and amorphous domains) have been in the spotlight, offering a rich and sophisticated toolbox for Janus nanomaterials. With careful surface and interfacial engineering, Janus CNM particles have demonstrated great potential as surface modifiers, emulsifiers, stabilizers, compatibilizers, and dispersants in emulsions, nanocomposites, and suspensions. Naturally derived Janus CNM particles offer a fascinating opportunity for scaling up the production of self-standing Janus CNM membranes. Nevertheless, most Janus CNM membranes to date are constructed by asymmetric fabrication or asymmetric modification without considering the Janus traits of CNM particles. More future research should focus on the self-assembly of Janus CNM particles into bulk self-standing Janus CNM membranes to enable more straightforward and sustainable approaches for Janus membranes. This review explores the fabrication, structure-property relationship, and Janus configuration mechanisms of Janus CNM particles and membranes. Janus CNM membranes are highlighted for their versatile applications in liquid, thermal, and light management. This review also highlights the significant advances and future perspectives in the construction and application of sustainable Janus CNM particles and membranes.