pH-Responsive Properties of Asymmetric Nanopapers of Nanofibrillated Cellulose

Nanomaterials
Maud CheminAna Villares

Abstract

Inspired by plant movements driven by the arrangement of cellulose, we have fabricated nanopapers of nanofibrillated cellulose (NFC) showing actuation under pH changes. Bending was achieved by a concentration gradient of charged groups along the film thickness. Hence, the resulting nanopapers contained higher concentration of charged groups on one side of the film than on the opposite side, so that pH changes resulted in charge-dependent asymmetric deprotonation of the two layers. Electrostatic repulsions separate the nanofibers in the nanopaper, thus facilitating an asymmetric swelling and the subsequent expanding that results in bending. Nanofibrillated cellulose was modified by 2,2,6,6-tetramethylpiperidin-1-yl)oxyl radical (TEMPO) oxidation at two reaction times to get different surface concentrations of carboxylic acid groups. TEMPO-oxidized NFC was further chemically transformed into amine-modified NFC by amidation. The formation of graded nanopapers was accomplished by successive filtration of NFC dispersions with varying charge nature and/or concentration. The extent of bending was controlled by the charge concentration and the nanopaper thickness. The direction of bending was tuned by the layer composition (carboxylic ...Continue Reading

References

Sep 10, 2003·Biomacromolecules·Denilson da Silva PerezMichel R Vignon
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Methods Mentioned

BETA
amidation

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