TEMPO oxidized cellulose thin films analysed by QCM-D and AFM

2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO) oxidized cellulose has quickly become a highly utilized material in the production of nanofibrillar cellulose (NFC) and a functionalization strategy for cellulosic materials. In this study we have prepared oxidized cellulose films by TEMPO oxidation and used a quartz crystal microbalance with dissipation monitoring to analyse changes in the film properties. Oxidation was performed at different pH values and reaction times for amorphous and NFC surfaces were also varied. By varying TEMPO oxidation conditions the carboxylation efficiency, stability, and topographical sensitivity of TEMPO oxidation can be optimized for production of a required functionalization level without causing unwanted damage to the cellulosic material. The topographical changes on oxidized cellulose films were further characterized by AFM. Although both surfaces reacted in a similar manner to oxidation, the NFC film was found to be more stable during the oxidation than amorphous cellulose film. The results in this article can be utilized for the functionalization of cellulosic materials in a more controlled manner and for tuning the required carboxylation levels without causing permanent changes to the functionalized cellulosic material.