Radicalization of lignocellulosic fibers, related structural and morphological changes.
The radicalization of unbleached lignocellulosic fibers obtained from thermomechanical (TMP) and chemothermomechanical (CTMP) pulps was performed in heterogeneous phase by reaction with dioxygen in the presence of N,N'-ethylenebis(salicylideneiminato)cobalt(II), [Co(salen)], as catalyst. Phenoxy cobalt radicals immobilized in fibers were observed by electron paramagnetic resonance (EPR) spectroscopy; their amount depends on the fiber swelling induced by reaction medium. The absolute concentration of such radicals in fibers, about 10(16) spin/g, reaches values 10 times higher than that of phenoxy radicals formed in similar oxidative reactions catalyzed by laccase. The generation of phenoxy cobalt radicals in fibers was related to structural changes of lignin units, detected by mono- and bidimensional nuclear magnetic resonance ((13)C NMR and 2D-HSQC) investigations, and to morphological modifications in fibers observed by scanning electron microscopy (SEM).
Canevali
Carmen
C
Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, Via R.Cozzi 53, 20125 Milano, Italy.
Orlandi
Marco
M
Zoia
Luca
L
Scotti
Roberto
R
Tolppa
Eeva-Liisa
EL
Sipila
Jussi
J
Agnoli
Francesca
F
Morazzoni
Franca
F
D002482:Cellulose / Q000032:analysis / Q000378:metabolism* / Q000648:ultrastructure*; D005609:Free Radicals / Q000032:analysis / Q000378:metabolism*; D008031:Lignin / Q000032:analysis / Q000378:metabolism* / Q000648:ultrastructure*; D018514:Plant Structures / Q000378:metabolism / Q000648:ultrastructure; D014934:Wood
D005609:Free Radicals; C036909:lignocellulose; D002482:Cellulose; D008031:Lignin