Biomacromolecules, Vol.13, No.3, 842-849, 2012
Relationship between Length and Degree of Polymerization of TEMPO-Oxidized Cellulose Nanofibrils
The influence of 2,2,6,6-tetrametylpiperidine-1-oxyl (TEMPO)-mediated oxidation of wood cellulose and the mechanical disintegration of oxidized cellulose in water on degree of polymerization determined by viscosity measurement (DPv) and the apparent length of the TEMPO-oxidized cellulose nanofibrils (TOCNs) was investigated. DPv values decreased from 1270 to 500-600 with increasing addition of NaClO in the TEMPO-mediated oxidation stage. The DPv values were further decreased by mechanical fibrillation in water. There is a linear relationship between the average fibril length and DPv; the lengths of TOCNs can be approximated from DPv using 0.5 M copper ethylenediamine as a solvent of both the cellulose and oxidized celluloses in TOCNs. Based on the cellulose fibril models and TEMPO oxidation mechanism, the depolymerization behavior of TOCNs is tentatively explained in terms of distribution of disordered regions in wood cellulose fibrils and formation of C6-aldehydes in cellulose fibrils during TEMPO-mediated oxidation.