FTIR-ATR analysis of the H-bond network of water in branched polyethyleneimine/TEMPO-oxidized cellulose nano-fiber xerog
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ORIGINAL RESEARCH
FTIR-ATR analysis of the H-bond network of water in branched polyethyleneimine/TEMPO-oxidized cellulose nano-fiber xerogels Giuseppe Paladini . Valentina Venuti . Vincenza Crupi Andrea Fiorati . Carlo Punta
. Domenico Majolino .
Received: 2 May 2020 / Accepted: 7 August 2020 Ó Springer Nature B.V. 2020
Abstract The present paper reports a detailed experimental vibrational analysis, performed by Fourier transform infrared spectroscopy in attenuated total reflectance geometry (FTIR-ATR), of water confined in the pores of cellulose nano-sponges (CNSs), prepared using TEMPO oxidized and ultra-sonicated cellulose nano-fibers (TOUS-CNFs) as three-dimensional scaffolds, and branched polyethyleneimine (bPEI) as the cross-linking agent. The analysis was carried out by varying hydration and cross-linker amount, with the aim of achieving a deep understanding of how the hydrogen bond (H-bond)
G. Paladini V. Venuti D. Majolino Department of Mathematical and Computer Sciences, Physical Sciences and Earth Sciences, University of Messina, Viale Ferdinando Stagno D’Alcontres 31, 98166 Messina, Italy V. Crupi (&) Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno D’Alcontres 31, 98166 Messina, Italy e-mail: [email protected]
scheme developed by engaged water molecules can play a role in the water adsorption process already observed at macroscopic level, furnishing at the same time evidence of a nano-porous network for CNSs. In particular, the combined investigation of the FTIRATR spectra of CNSs hydrated with H2O and D2O allowed for the selective analysis of vibrational modes of entrapped water molecules, namely O–H stretching and HOH bending modes. As main result, a destructuring effect of hydration on the H-bond pattern of interfacial water molecules is revealed, associated to structural modifications of the bPEI/TOUS-CNFs network previously detected by small angle neutron scattering (SANS) technique. It turned out to be more relevant for low bPEI amounts. In addition, a supercooled behavior of entrapped water molecules is detected, supporting the idea of a nano-confinement for water in these systems. The obtained information can be very helpful in view of all the possible applications of bPEI-TOCNF sponges as efficient adsorbent materials, especially for water remediation.
A. Fiorati C. Punta Department of Chemistry, INSTM Local Unit, Materials, and Chemical Engineering ‘‘G. Natta’’, Politecnico di Milano, Via Mancinelli 7, 20131 Milan, Italy e-mail: [email protected] C. Punta C. N. R. Istituto di Chimica del Riconoscimento Molecolare (ICRM), Milan, Italy
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Cellulose
Graphic abstract
Keywords Cellulose nano-fibers TEMPO FTIRATR technique Nano-porous materials O–H stretching HOH bending
Introduction The development and characterization of ‘‘green’’ materials have gained, in recent years, a considerable attention due to the high demand to reduce, in a smart w
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