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.