In Nature, cellulose and water coexist in plants. The living wood is water saturated and the water along with the cellulose play a key role for its mechanical properties. On the other hand, in man-made cellulosic materials such as nanocellulose composites, moisture at the interface makes it poor and decreases the material's mechanical performance. In both cases, a fundamental understanding of the interface between cellulose and water is desirable. Experimental tools such as Nuclear Magnetic Resonance (NMR) and vibrational spectroscopy have been used for investigation but many questions remains. Water is attracted to the cellulose surface but how its structure and dynamics is affected is not clear. The vibrational spectrum of cellulose/water in the region of O-H stretching is hard to resolve experimentally due to overlapping of many different signals from both cellulose and water. Despite this, many experimental studies are focused on the changes of cellulose/water vibrational spectrum with moisture and several techniques have been applied in order to deconvolute and assign the signals to specific motions in the system. One common assignment is to address one peak at ~3200 cm-1 to strongly bound and at ~3600 cm-1to weakly bound water. The basis of this assignment is on the other hand not clear.  In order to reveal details of the cellulose/water interface we calculated vibrational spectrum from molecular dynamics simulations. The water O-H stretching signal was clearly affected by the presence of a cellulose surface. We compare modeling and experimental results, investigate the effect of moisture saturation and also what happens when the water is confined by cellulose.

Vibrational spectrum of the cellulose-water interface investigated by atomistic simulations

247th National Meeting (2014)

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