Nanocelluloses have been emerging as an outstanding building block for the promotion of circular economy concepts. Alongside tempo-oxidized cellulose nanofibers and other chemically defibrillated nanofibers, mechanically fibrillated cellulose nanofibers (CNFs) are currently amongst the most investigated in materials science. CNFs can form robust networks on their own such as nanopaper, porous materials with a low density and a high surface, and can be imbued with functionalities when they serve the role of a cohesive matrix. However, the characterization of their morphological characteristics still poses significant challenges because of their rather high aspect ratio preventing the characterization of both their length, and their diameter simultaneously. Achievement of an in-depth characterization is required to facilitate the prediction of the properties of the materials they form. In the present work we describe an important step forward towards a complete description of the morphological characteristics of CNFs. We introduce two new concepts, negative contrast imaging scanning electron microscopy (SEM), where CNFs were spotted onto a variety of metallic surfaces prior to SEM imaging (optimized for contrast). The dimensionalities obtained with the latter method were cross-correlated with a thorough morphological mapping by atomic force microscopy to obtain a precise description of the cross sectional area of CNFs. Appropriate physical considerations such as deconvolution of tip-based artefacts and substrate adhesion of the fibers were used to correct the data obtained. The methodology was aimed for cost- and time-efficiency as nanocelluloses are regularly employed for low-cost and high-volume applications. The values we obtained for cross-sectional area, surface area and aspect-ratio of the fibrils differ substantially to the generally used value These values were used to predict the behavior of particulated nanocomposites and were shown to provide accurate description of the fiber network and their interaction with particles. Combined with the justifications for accuracy in the morphological description of CNF and formed composites, the present work highlights important considerations for future works involving nanocelluloses.

Facile and comprehensive approach, accounting for substrate interactions, for the characterization of the dimensions of cellulose nanofibrils

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.