MOLECULAR DYNAMICS STUDY OF THE DISRUPTION OF H-BONDS BY WATER MOLECULES AND ITS DIFFUSION BEHAVIOR IN AMORPHOUS CELLULOSE

Abstract

Hydrolysis is an important component of the aging of cellulose, and it severely affects the insulating performance of cellulosic materials. The diffusion behavior of water molecules in amorphous cellulose and their destructive effect on the hydrogen bonding structure of cellulose were investigated by molecular dynamics. The change in the hydrogen bonding structure indicates that water molecules have a considerable effect on the hydrogen bonding structure within cellulose: both intermolecular and intramolecular hydrogen bonds decreased with an increase in ingressive water molecules. Moreover, the stabilities of the cellulose molecules were disrupted when the number of intermolecular hydrogen bonds declined to a certain degree. Both the free volumes of amorphous cells and water molecule-cellulose interaction affect the diffusion of water molecules. The latter, especially the hydrogen bonding interaction between water molecules and cellulose, plays a predominant role in the diffusion behavior of water molecules in the models of which the free volume rarely varies. The diffusion coefficient of water molecules has an excellent correlation with water molecule-cellulose interaction and the average hydrogen bonds between each water molecule and cellulose; however, this relationship was not apparent between the diffusion coefficient and free volume.

Changes in the hygroscopic behavior of cellulose due to variations in relative humidity

“…Structurally, it is estimated that there is a thin layer of non-crystalline cellulose on the surfaces of fibrils (Atalla et al 2008;Fernandes et al 2011;Leppänen et al 2009;Salmén and Bergström 2009;Weatherwax 1977) that could be prone to hornification and interfibrillar hydrogen bonding to either cellulose or hemicellulose (Leppänen et al 2009;Mohan et al 2012). Modeling studies on a molecular level have also suggested that intrafibrillar restructuring can take place within the first molecular layers (Heiner et al 1998;Matthews et al 2006;Maurer et al 2013), however, the nature and extent of such restructuring depend on the amorphous fraction and crystal structure of the surface (Kulasinski et al 2017;Liao et al 2012;Yamane et al 2006). Figure 1 shows the possible changes including surface irregularities and hydrogen bond changes (red lines) from inter-chain (bulk cellulose, Fig.…”

Cosmography and the redshift drift in Palatini $$f({{\mathcal {R}}})$$ f ( R ) theories

“…While constraints from the combination of large-scale structure, CMB data and SNIa observations could reduce the allowed space-parameter to a small region around the ΛCDM cosmology (β ≈ 10 −3 ) [13,42], other analyses combining CMB and BAO data yield (n, β) = (0.027 +0.42 −0.23 , 4.63 +2.73 −10.6 ) [8]. These values were later improved with combinations of CMB, SNIa and BAO data, along with Hubble parameter estimations [55][56][57], as well as data coming from strong lensing analysis [14,58]. Cosmographic constraints were obtained from the examination of the deceleration parameter [48] and the so-called statefinder diagnostic [46].…”

“…A cosmographic approach. The geometric and kinematic properties of the metric (14) are characterised by the so-called kinematic parameters, defined as the coefficients of the series expansion of the scale factor around t 0 . In particular,…”

“…The dependence of the function f with the scalar curvature R introduces a set of constants, characterising a particular family of f (R)-cosmologies. The particular form of f as well as a range of suitable values for the constants must be chosen taking into account several criteria, such as the appropriate sequence of cosmological eras [8], the correct dynamics of cosmological density perturbations [9], as well as the correct weak-field limit at both the Newtonian and post-Newtonian levels [10], the well-posedness of the Cauchy problem [11], and the correct fit of cosmological observables [12][13][14]. 1 Among the observable quantities with the potential of discriminating between f (R)-models and those based on GR, particular attention was recently given to the time variation of the cosmological redshift z due to the variation of the expansion rate of the universe, namely the redshift drift (RD).…”

Revisiting the coincidence problem in f(R) gravitation

“…42 −0.23 , 4.63 +2.73 −10.6 ) [58]. These estimates were further upgraded with amalgamations of BAO, SNIa, CMB data, coupled with Hubble parameter evaluations [71,72], and strong lensing analysis [73,74]. From the investigation of deceleration parameter and statefinder diagnostics, cosmographic constraints were reported in [59,61].…”