In this work, water molecule interactions with nanocellulose and conductive nanocellulose films were studied. The conductive films consisted functionalized multi-walled carbon nanotubes (MWCNT) dispersed in a network of TEMPO-oxidized cellulose nanofibrils (TOCNF). For the first time, adsorption and desorption of water vapor into TOCNF and TOCNF-MWCNT thin films were studied in a climatic chamber equipped with a quartz crystal microbalance (QCM). Herein, the effect of film thickness on water-uptake and swelling was investigated at 30-60% relative humidity and temperature range 25-50 °C. Both films showed fast response to humidity variations by 10% (TOCNF) and 20% (TOCNF-MWCNT) of mass increase. Thus, MWCNT made the fibril network more accessible to water molecules. Besides, by increasing temperature from 25 to 50 °C, the water adsorption decreased by 13% at similar humidity conditions.<br/>Further, humidity sensing behavior was characterized by measuring resistance of the films printed on glass and paper substrates. It was observed both films behaved similarly that resistivity followed humidity variation in a cyclic manner from 20 to 60% humidity, i.e. the resistance increased by 12-14% with the increase of relative humidity (See figure). Thus, the paper substrate did not affect the humidity sensing compared to glass counterpart. Further, the effect of MWCNT concentration was analyzed and it was concluded that a humidity sensitive system was produced with films containing only 10% MWCNT. These humidity responsive conductive films provide a great potential to develop biobased humidity sensors for smart packaging applications to monitor conservation conditions of food and medicine products.

Water molecule interactions with nanofibrillated cellulose and its application in humidity sensing

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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