Molecular Mass and Molecular-Mass Distribution of TEMPO-Oxidized Celluloses and TEMPO-Oxidized Cellulose Nanofibrils

Abstract

Native wood cellulose was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and the fibrous TEMPO-oxidized celluloses (TOCs) thus obtained were disintegrated in water to prepare TOC nanofibrils (TOCNs). The carboxyl groups of TOCs and TOCNs were methyl-esterified, and the methylated samples were dissolved in 8% LiCl/N,N-dimethylacetamide for size-exclusion chromatography/multiangle laser-light scattering (SEC-MALLS) analysis to obtain their molecular-mass (MM) values and MM distributions (MMDs). The results showed that remarkable depolymerization occurred in TOCs and TOCNs and depended on the oxidation and sonication conditions. Because single peaks without bimodal patterns were observed in the MMDs for all of the TOC and TOCN samples, depolymerization may have randomly occurred on whole cellulose molecules and oxidized cellulose molecules in the microfibrils during these treatments. Compared with the MM values obtained by SEC-MALLS, the intrinsic viscosities of TOCs dissolved in 0.5 M copper ethylenediamine solution provided lower MM values owing to depolymerization during the dissolution and postreduction processes.

Mechanism of TEMPO-oxidized cellulose nanofibril film reinforcement with poly(acrylamide)

“…The viscosity-average degrees of polymerization (DP v ) of SBKP, NaClO 2 -treated TOC, and TOCNs were measured at 20°C using 0.5 M copper ethylenediamine as the solvent and a Cannon-Fensketype capillary viscometer. The intrinsic viscosities of SBKP, NaClO 2 -treated TOC, and TOCNs were converted to DP v values using the Mark-HouwinkSakurada equation (Hiraoki et al 2015). The sodium ion contents of the aqueous PAM/TOCN mixtures were determined using inductively coupled plasma optical emission spectroscopy (Agilent 720-ES).…”

Creation of a new material stream from Japanese cedar resources to cellulose nanofibrils

“…The crystallinity index decreased slightly with increasing amounts of added NaClO, but the (2 0 0) crystal size was roughly constant,~3 nm, for all the TOCs-NaBH 4 . These results show that C6-carboxylation by TEMPO-mediated oxidation occurs on the crystalline cellulose microfibril surfaces and in the disordered regions periodically present along the longitudinal direction of the cellulose microfibrils [25].…”

“…The intrinsic viscosities [η] of the solutions were measured using a capillary viscometer, and the viscosityaverage degrees of polymerization (DP v ) were calculated from the [η] values using the Mark-Houwink-Sakurada equation: [η] = 2.84 × DP v 0.67 [25].…”

Structural Characterization and Modifications of Surface-oxidized Cellulose Nanofiber

“…The experimental scheme for TOCs and TOCNs to be subjected to SEC-MALLS analysis through methyl esterification is illustrated in Fig. 5 42), 43) . When TOCs were prepared from a wood cellulose by TEMPO/NaBr/NaClO oxidation system in water at pH 10 with various amounts of NaClO added, the peak position in the molecular mass distribution shifted to the lower molecular-mass direction as the amount of NaClO added was increased (Fig.…”