Tsuguyuki Saito

Never-dried and once-dried hardwood celluloses were oxidized by a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated system, and highly crystalline and individualized cellulose nanofibers, dispersed in water, were prepared by mechanical treatment of the oxidized cellulose/water slurries. When carboxylate contents formed from the primary hydroxyl groups of the celluloses reached approximately 1.5 mmol/g, the oxidized cellulose/water slurries were mostly converted to transparent and hig

Never-dried native celluloses (bleached sulfite wood pulp, cotton, tunicin, and bacterial cellulose) were disintegrated into individual microfibrils after oxidation mediated by the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical followed by a homogenizing mechanical treatment. When oxidized with 3.6 mmol of NaClO per gram of cellulose, almost the totality of sulfite wood pulp and cotton were readily disintegrated into long individual microfibrils by a treatment with a Waring Blendor, yieldi

Cellulose cotton linter was oxidized with sodium hypochlorite with catalytic amounts of sodium bromide and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) under various conditions. After this TEMPO-mediated oxidation, water-insoluble fractions were collected and characterized in terms of carboxylate and aldehyde contents, crystallinities and crystal sizes, degrees of polymerization, morphology, and water retention values. Carboxylate and aldehyde groups were introduced into the water-insolu

A new catalytic oxidation using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) and NaClO is applied to hardwood cellulose in water at 60 °C and pH 6.8 with NaClO(2) used as a primary oxidant. The oxidized celluloses with carboxylate content of approximately 0.8 mmol/g were convertible to highly crystalline and individual fibrils 5 nm in width and at least 2 μm in length by disintegration in water. The oxidized celluloses had no aldehyde groups, and high degrees of polymerization of more than 900.

We report the mechanical strength of native cellulose nanofibrils. Native cellulose nanofibrils, purified from wood and sea tunicate, were fully dispersed in water via a topochemical modification of cellulose nanofibrils using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a catalyst. The strength of individual nanofibrils was estimated based on a model for the sonication-induced fragmentation of filamentous nanostructures. The resulting strength parameters were then analyzed based on fracture

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 t

In living organisms, nanoscale building blocks are well organized into a nearly defect-free arrangement, leading to sophisticated hierarchical structures that exhibit high mechanical strengths and functionalities. Cellulose nanofibrils are representative building blocks in nature and have raised great interest as excellent structural materials, originating from the most abundant bioresource, wood biomass. Here, we report integration controls of the cellulose nanofibrils that have been completely

Scalability is a common challenge in the structuring of nanoscale particle dispersions, particularly in the drying of these dispersions for producing functional, porous structures such as aerogels. Aerogel production relies on supercritical drying, which exhibits poor scalability. A solution to this scalability limitation is the use of evaporative drying under ambient pressure. However, the evaporative drying of wet gels comprising nanoscale particles is accompanied by a strong capillary force.

The nematic structuring of cellulose nanofibers (CNFs) is proposed as a nanostructural engineering tool for exploiting the potential of CNFs in conceptually new "transparent papers". The nematic-structured CNF papers exhibit superior mechanical properties, optical transparency, gas-barrier properties, heat transfer properties and electrical resistivity, compared with conventional randomly-structured CNF papers.