Softwood and hardwood holocelluloses were subjected to TEMPO-mediated oxidation under alkaline and neutral conditions to prepare TEMPO-oxidized holocellulose nanofibrils (TOHCNs). Carboxylate contents, weight recovery ratios and neutral sugar compositions of TEMPO-oxidized holocelluloses thus obtained were measured. Significant amounts of xylan originally present in hardwood holocelluloses remained in TEMPO-oxidized holocelluloses prepared under neutral conditions, while almost no neutral sugars originating from hemicelluloses were present in TEMPO-oxidized holocelluloses prepared under alkaline conditions; most of hemicelluloses in holocelluloses degrade to water-soluble compounds during TEMPO-mediated oxidation under alkaline conditions. Crystal widths of cellulose I in the original holocelluloses (~3 nm) measured using XRD patterns were mostly unchanged before and after TEMPO-mediated oxidation, showing that oxidation of C6-primary hydroxyls to C6-carboxylates takes place selectively on crystalline cellulose microfibrils. TOCN widths determined in water using AFM were also ~3nm, and thus consistent with those determined using XRD. Average TOCN lengths prepared from holocelluloses were around 600 nm, which was greater than those prepared from softwood bleached kraft pulp under the same conditions.

Effect of hemicelluloses on properties of TEMPO-oxidized cellulose nanofibrils prepared from softwood and hardwood holocelluloses under alkaline and neutral conditions

247th National Meeting (2014)

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