There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

This critical review provides a processing-structure-property perspective on recent advances in cellulose nanoparticles and composites produced from them. It summarizes cellulose nanoparticles in terms of particle morphology, crystal structure, and properties. Also described are the self-assembly and rheological properties of cellulose nanoparticle suspensions. The methodology of composite processing and resulting properties are fully covered, with an emphasis on neat and high fraction cellulose composites. Additionally, advances in predictive modeling from molecular dynamic simulations of crystalline cellulose to the continuum modeling of composites made with such particles are reviewed (392 references).

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Cellulose nanomaterials review: structure, properties and nanocomposites

Cellulose constitutes the most abundant renewable polymer resource available today. As a chemical raw material, it is generally well-known that it has been used in the form of fibers or derivatives for nearly 150 years for a wide spectrum of products and materials in daily life. What has not been known until relatively recently is that when cellulose fibers are subjected to acid hydrolysis, the fibers yield defect-free, rod-like crystalline residues. Cellulose nanocrystals (CNs) have garnered in the materials community a tremendous level of attention that does not appear to be relenting. These biopolymeric assemblies warrant such attention not only because of their unsurpassed quintessential physical and chemical properties (as will become evident in the review) but also because of their inherent renewability and sustainability in addition to their abundance. They have been the subject of a wide array of research efforts as reinforcing agents in nanocomposites due to their low cost, availability, renewability, light weight, nanoscale dimension, and unique morphology. Indeed, CNs are the fundamental constitutive polymeric motifs of macroscopic cellulosic-based fibers whose sheer volume dwarfs any known natural or synthetic biomaterial. Biopolymers such as cellulose and lignin and † North Carolina State University. ‡ Helsinki University of Technology. Dr. Youssef Habibi is a research assistant professor at the Department of Forest Biomaterials at North Carolina State University. He received his Ph.D. in 2004 in organic chemistry from Joseph Fourier University (Grenoble, France) jointly with CERMAV (Centre de Recherche sur les Macromolecules Vegetales) and Cadi Ayyad University (Marrakesh, Morocco). During his Ph.D., he worked on the structural characterization of cell wall polysaccharides and also performed surface chemical modification, mainly TEMPO-mediated oxidation, of crystalline polysaccharides, as well as their nanocrystals. Prior to joining NCSU, he worked as assistant professor at the French Engineering School of Paper, Printing and Biomaterials (PAGORA, Grenoble Institute of Technology, France) on the development of biodegradable nanocomposites based on nanocrystalline polysaccharides. He also spent two years as postdoctoral fellow at the French Institute for Agricultural Research, INRA, where he developed new nanostructured thin films based on cellulose nanowiskers. Dr. Habibi’s research interests include the sustainable production of materials from biomass, development of high performance nanocomposites from lignocellulosic materials, biomass conversion technologies, and the application of novel analytical tools in biomass research. Chem. Rev. 2010, 110, 3479–3500 3479

Cellulose nanocrystals: chemistry, self-assembly, and applications.

Propriétés d’écoulement et de structure des couches de polarisation de concentration lors de l’ultrafiltration tangentielle de colloïdes, sondés par SAXS et micro PIV in-situ.

Macromol. Mater. Eng. 11/2011

Characterization of hydrodynamic conditions and structural organization during cross-flow ultra-filtration : application to bio-refinery

Receiving considerable interest in recent years, the reducing ends of cellulose nanocrystals (CNCs) with heterogeneous groups and different reactivity from surface chemistry contribute to the development of new strategies for regioselective modification and performance tailoring for this building block of natural biomass. However, the understanding of the phenomena involved at the reducing end is still at the research stage for cellulose chains, usually in dissolved form in a solvent, but lacks extensive investigation for nanocrystals, existing in the form of suspensions. Two issues are explored in this study. The first one concerns the comprehensive analysis of various conditions and parameters for the introduction of aldehyde groups at the reducing end of CNCs. The second investigates the influence of end-modified species on the crystalline reconfiguration of nanocrystals during mercerization. Quantitative measurements of the content of reducing end aldehyde groups are carried out for nine nanocellulose samples, offering scientific evidence to obtain more aldehyde groups available at the reducing end of CNCs for future studies. Furthermore, four species of CNCs with various chemical structures and macroscopic properties are modified at the reducing ends, and their reorganization as type-II nanocrystals during mercerization is investigated. The results indicate a critical effect of the steric hindrance of end species on the crystalline reconfiguration of nanocrystals, providing inspiration for a possible molecular structure and asymmetric modification for this ageless nanomaterial. 

Regioselective Modification at Reducing End Aldehydes of Cellulose Nanocrystals and Mercerization

L'interet pour la nanocellulose croit de facon exponentielle. Au cours de la derniere decennie, ce nanomateriau biosource a ete essentiellement utilise dans les nanocomposites pour ses proprietes de renfort. Ses dimensions a l'echelle nanometrique et sa capacite a former un reseau enchevetre nanoporeux ont cependant favorise l'emergence de nouvelles applications a haute valeur ajoutee. L'emballage est une application potentielle de la nanocellulose. Des proprietes mecaniques, optiques et barrieres prometteuses sont des caracteristiques encourageantes.

Alain Dufresne

Papers

Propriétés d’écoulement et de structure des couches de polarisation de concentration lors de l’ultrafiltration tangentielle de colloïdes, sondés par SAXS et micro PIV in-situ.

Macromol. Mater. Eng. 11/2011

Characterization of hydrodynamic conditions and structural organization during cross-flow ultra-filtration : application to bio-refinery

Regioselective Modification at Reducing End Aldehydes of Cellulose Nanocrystals and Mercerization

Nanoparticules cellulosiques : propriétés et applications à l'emballage