Nanocellulose with unique character converted directly from plants without intensive mechanical disintegration.

TEMPO oxidized nano-fibrillated cellulose (TONFC) has been used in different applications including biomedical, packing materials, paints and cosmetics because of its higher transparency, mechanical properties and better biocompatibility. However, pulping is always required to remove lignin and hemicellulose, and high-energy homogenization is required to defibrillate cellulose bundle into filament. Therefore, it is desirable to find a novel way to get TONFC with high carboxyl content without intensive mechanical disintegration. In this work, nanocellulose (TOHOLO) with higher carboxyl groups (2.2 ± 0.2 mmol/g) and smaller size (length = 400-685 nm and diameter = 5.9 nm) was prepared by a two-step strategy without intensive mechanical homogenization. In addition to the advantages in terms of diameter and carboxyl groups, TOHOLO showed better transparency and re-dispersibility as well as higher mechanical properties (122.8 MPa) compared to previous reports. Furthermore, for high carboxyl group and dispersibility, the TOHOLO can be used as a reinforcing filler to fabricate nanocomposites. The reinforced PVA fibers show a tensile strength of 484.4 MPa, which is about 170 % higher than comparison samples (PVA/TOCN-M, 291.9 MPa).

Scalable Nano Building Blocks of Waterborne Polyurethane and Nanocellulose for Tough and Strong Bioinspired Nanocomposites by a Self-Healing and Shape-Retaining Strategy.

Nature has given us significant inspiration to reproduce bioinspired materials with high strength and toughness. The fabrication of well-defined three-dimensional (3D) hierarchically structured nanocomposite materials from nano- to the macroscale using simple, green, and scalable methods is still a big challenge. Here, we report a successful attempt at the fabrication of multidimensional bioinspired nanocomposites (fiber, films, plates, hollow tubes, chair models, etc.) with high strength and toughness through self-healing and shape-retaining methods using waterborne polyurethane (WPU) and nanocellulose. In our method, the prepared TEMPO oxide cellulose nanofiber (TOCNF)-WPU hybrid films show excellent moisture-induced self-healing and shape-retaining abilities, which can be used to fabricate all sorts of 3D bioinspired nanocomposites with internal aligned and hierarchical architectures just using water as media. The tensile and flexural strength of the self-assembled plate can reach 186.8 and 193.2 MPa, respectively, and it also has a high toughness of 11.6 MJ m-3. Because of this bottom-up self-assembly strategy, every multidimensional structure we processed has high strength and toughness. This achievement would provide a promising future to realize a large-scale and reliable production of various sorts of bioinspired multidimensional materials with high strength and toughness in a sustainable manner.

Strategy to Fabricate a Strong and Supertough Bio-Inspired Fiber with Organic-Inorganic Networks in a Green and Scalable Way.

Green and scalable production of some fibrous materials with higher fracture energy has long been the goal of researchers. Although some progress has been made in recent years in the research of materials with high fracture energy, inspired by the fiber structure of spider silk, it is still a great challenge to produce artificial fibers with extremely high toughness using a simple and green process. Here, we use the molecular and nanoscale engineering of calcium phosphate oligomers (CaP, < 1 nm) and waterborne polyurethanes (WPU) macromolecules that have strong interactions to form organic-inorganic networks just like ß-sheet crystalline and flexible amorphous regions in spider silk. Through a simple and green route based on widespread paper string processing techniques, we fabricate a strong and supertough bioinspired fiber with a high strength (442 MPa), which is 7-15 times higher than the strength of counterpart PU (20-30 MPa), and a super toughness (640 MJ m-3), which is 2-3.5 times higher than the toughness of spider dragline silk. This technique provides a strategy for industrially manufacturing spider fiber-like artificial fibers with a super toughness.