Effect of hydration on the H-bond dynamics of adsorbed water in cellulose/polyethyleneimine nano-sponges probed by 2D-COS and PCMW2D two-dimensional FTIR correlation spectroscopy

In this work, generalized (2D-COS) and perturbation-correlation moving window (PCMW2D) two-dimensional correlation analyses were applied on a set of hydration-dependent Fourier Transform Infrared Spectroscopy in Attenuated Total Reflectance Geometry (FTIR-ATR) data of cellulose nano-sponges (CNSs) consisting of TEMPO-oxidized cellulose nanofibrils (TOCNF) as three-dimensional scaffolds, and branched polyethyleneimine (bPEI) as cross-linker. The aim was to get insights, starting from the computation of synchronous (SCMs) and asynchronous (ACMs) 2D-COS and PCMW2D correlation maps, into the effect of hydration on the hydrogen bond (H-bond) dynamics of water molecules closely attached to the cellulose nanofibrils (interfacial water), based on the assessment of the complex sequence of events affecting the O-H modes of the CNS material at different bPEI:TOCNF (w/w) ratios. The possibility to highlight the time-dependent dynamical evolution exhibited by complex cellulose-based materials, not accessible through conventional 1D FTIR-ATR analysis, can provide useful notions for the development and optimization of CNSs-based devices for different applications, including water remediation, drug-delivery and heterogeneous catalysis.