Surface properties of distinct nanofibrillated celluloses assessed by inverse gas chromatography

• Nanocelluloses were distinguished from each other for their surface properties.
• Dispersion component of the surface energy (γsd) at 40 °C was of 42–52 mJ m−2.
• Higher γsd value was found for enzymatic nanocellulose than for TEMPO-oxidised ones.
• For TEMPO-nanocelluloses acidity/basicity ratio increased with the fibrillation.
• Results may have interest in the composites production area/coatings applications.

The adhesion and surface properties of nanocelluloses are an important issue to consider when using this material for composites production, in food packaging or coatings, as well as for determining the influence of added functional groups. In the present work, the surface properties of two nanofibrillated celluloses obtained by mild 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation with distinct mechanical treatment intensity in a homogenizer (5 and 15 passes), and one nanofibrillated cellulose obtained by enzymatic process, were thoroughly assessed by inverse chromatography, at infinite dilution conditions. The dispersion component of the surface energy (γsd) was 42–46 mJ m−2 at 40 °C for the TEMPO nanofibres and 52 mJ m−2 for the enzymatic nanocellulose. It was confirmed, based on the determination of the specific components of the works of adhesion and enthalpies of adsorption with polar probes, that the surfaces of the materials have a more Lewis acidic than Lewis basic character. Regarding TEMPO nanofibres, a slight increase of Lewis acidity/basicity ratio seemed to occur for the more nanofibrillated material (15-passes). Higher specific interactions with polar probes were found for enzymatic nanocellulose. The higher values of γsd and specific interactions observed for the enzymatic nanocellulose could partly be due to the higher crystallinity of this sample. On the other hand, the increase of the acidity/basicity ratio (as well as of the γsd value) for the 15-passes versus 5-passes TEMPO nanofibres was attributed to a higher exposition of the hydroxyl groups of cellulose at the surface of the former material.

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