Direct Preparation of Nanocelluloses of Tunable Lengths from Native Wood Via Alkaline Periodate Oxidation

摘要

Herein, cellulose nanofibers (PO-CNFs) and cellulose nanocrystals (PO-CNCs) are prepared directly from native softwood spruce and hardwood beech via the same alkaline periodate oxidation under equal conditions. PO-CNFs and PO-CNCs are obtained by simply regulating the reaction time between 2 and 7 d. Of particular note, the preparation of CNFs is achieved using the alkaline periodate oxidation. PO-CNFs obtained from spruce and beech have average diameters of 7.2 +/- 3.1 and 6.8 +/- 3.0 nm as well as average lengths of 487.1 +/- 69.0 and 452.1 +/- 80.0 nm, respectively. The PO-CNCs obtained from spruce and beech are 4.6 +/- 2.0 and 4.8 +/- 2.5 nm in diameter as well as 181.6 +/- 49.4 and 168.4 +/- 59.0 nm in length, respectively. These nanocelluloses contain carboxy groups that enable good colloidal stability of nanocelluloses in water. The nanocellulose content isolated from spruce and beech increase with the reaction time and reach 1.35 +/- 0.20 and 1.24 +/- 0.10 mmol g(-1) after oxidation for 7 d, respectively. Both PO-CNFs and PO-CNCs can be used for the formation of highly transparent films with good mechanical properties.