  Cellulose disassembly is an important issue in designing nanostructures using
cellulose-based materials. In this work, we present a joint of experimental and
theoretical study addressing the disassembly of cellulose nanofibrils. Through
2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mediated oxidation processes,
combined with atomic force microscopy results, we find the formation of
nanofibers with diameters corresponding to a single cellulose polymer chain.
The formation of these polymer chains is ruled by repulsive electrostatic
interactions between the oxidized chains. Further first-principles calculations
have been done in order to provide an atomistic understanding the cellulose
disassembling processes, focusing on the balance of the interchain and
intersheet interactions upon oxidation. Firstly we analyse these interaction in
pristine systems, where we found the intersheet interaction stronger than the
interchain one. In the oxidized systems, we have considered the formation of
(charged) carboxylate groups along the inner sites of elementary fibrils. We
show a net charge concentration on the carboxylate groups, supporting the
emergence of repulsive electrostatic interactions between the cellulose
nanofibers. Indeed, our total energy results show that the weakening of the
binding strength between the fibrils is proportional to the concentration and
the net charge density of the carboxylate group. Moreover, by comparing
interchain and intersheet binding energies, we found that most of the
disassembly processes should take place by breaking the interchain
O--H$\cdots$O hydrogen bond interactions, and thus supporting the experimental
observation of single and double cellulose polymeric chains.
