Phase Behavior of Acetylated Cellulose Nanocrystals and Origins of the Cross-Hatch Birefringent Texture

Advances in Small Angle Neutron Scattering on Polysaccharide Materials

Polysaccharide materials and biomaterials gain the focus of intense research owing to their great versatility in chemical structures and modification possibilities, as well as their biocompatibility, degradability, and sustainability features. This review focuses on the recent advances in the application of SANS on polysaccharide systems covering a broad range of materials such as nanoparticulate assemblies, hydrogels, nanocomposites, and plant-originating nanostructured systems. It motivates the use of SANS in its full potential by demonstrating the features of contrast variation and contrast matching methods and by reporting the methodologies for data analysis and interpretation. As these soft matter systems may be organized in multiple length scales depending on the interactions and chemical bonds between their components, SANS offers exceptional and unique opportunities for advanced characterization and optimization of new nanostructured polysaccharide materials.

Liquid-crystalline assembly of spherical cellulose nanocrystals

Rod-shaped cellulose nanocrystals (CNCs), also called cellulose nanorods (CNRs), possess anisotropic properties that allow for their self-organization into chiral nematic liquid crystals. Interestingly, spherical cellulose nanocrystals (cellulose nanospheres, CNSs) have also been shown to form a chiral liquid-crystalline phase in recent years. Herein, to understand how the similar assembly takes places as particle dimension changes, the organization features of CNSs were investigated. Results of this study demonstrate that above a critical concentration in suspension, CNSs organize into a liquid-crystal phase consisting of periodically parallel-aligned layer structures. This structure persists after suspension drying. In comparison with CNRs, the alignment of CNSs exhibits a shorter layer distance, lower order degree, and weaker long-range orientation. To explain the early stages of tactoid formation, a "caterpillar-like" model was proposed, which was captured by freezing the CNS suspension in an intermediate aggregation state. This structure serves as the fundamental unit for further liquid-crystal assembly.

Dispersion preparation, characterization, and dosimetric analysis of cellulose nano-fibrils and nano-crystals: Implications for cellular toxicological studies

The characterization of cellulose-based nanomaterial (CNM) suspensions in environmental and biological media is impaired because of their high carbon content and anisotropic shape, thus making it difficult to derive structure activity relationships (SAR) in toxicological studies. Here, a standardized method for the dispersion preparation and characterization of cellulose nanofibrils (CNF) and nanocrystals (CNC) in biological and environmental media was developed. Specifically, electron microscopy was utilized and allowed to specify optimum practices for efficiently suspending CNF and CNC in water and cell culture medium. Furthermore, a technique for measuring the in vitro particle kinetics of CNF and CNC suspended in cell culture medium utilizing fluorescently tagged materials was developed to assess the delivery rate of such CNM at the bottom of the well. Interestingly, CNF were shown to settle and create a loosely packed layer at the bottom of cell culture wells within a few hours. On the contrary, CNC settled gradually at a significantly slower rate, highlighting the discordance between administered and delivered mass dose. This work is both novel and urgent in the field of environmental health and safety as it introduces well-defined techniques for the dispersion and characterization of emerging, cellulose-based engineered nanomaterials. It also provides useful insights to the in vitro behavior of suspended anisotropic nanomaterials in general, which should enable dosimetry and comparison of toxicological data across laboratories as well as promote the safe and sustainable use of nanotechnology.