Watching cellulose grow – Kinetic investigations on cellulose thin film formation at the gas–solid interface using a quartz crystal microbalance with dissipation (QCM-D)

The conversion of trimethylsilyl cellulose (TMSC) to cellulose films via acid vapor hydrolysis is investigated at the gas solid interface in situ, in real time and under ambient conditions using the QCM-D technique. For this purpose, a permanent flow of gaseous HCl is employed which reacts with TMSC spun on QCM sensors to form cellulose films. The kinetics behind this reaction is elucidated and reveals first order. This desilylation reaction proceeds via a fast first phase (k = 3.01 × 10−3 s−1) and a second slower phase (k = 6.29 × 10−5 s−1) where less accessible silyl groups are cleaved off. Besides kinetics, film thicknesses have been determined using the QCM method. Moreover, the influence of the acid concentration on the kinetics and layer thickness was studied. A comparison between the materials synthesized in the QCM chamber with those obtained by classical vapor phase hydrolysis does not show any differences in the surface characteristics and composition as proven by X-ray photoelectron spectroscopy, atomic force microscopy, and wettability studies.