Atomistic Modeling of the Adsorption of Benzophenone onto Cellulosic Surfaces

Abstract

The interaction between cellulosic material and benzophenone was studied by molecular modeling. A model of the crystalline part of a native microfibril was built from previously published coordinates of the I allomorph. This model presents three faces, namely (200), (110), and (11 h0), of about the same surface area. The energetical and geometrical characteristics of the benzophenone adsorption onto this microfibril were studied with a Monte Carlo protocol. It was shown that the interaction does occur on the three faces and was stabilized by both van der Waals and electrostatic forces. On the hydrophobic (200) face, a large number of interacting sites without specific geometry were sampled by the adsorbing molecule. The hydrophilic surfaces, (110) and (11 h0), also have many interaction sites, but in contrast, the orientation of the adsorbed molecules is more strict. These two hydrophilic surfaces display equivalent behavior. Three surfaces (crystalline (11 h0) and (200) and amorphous) subjected to periodic boundary conditions were also generated to study the process of the benzophenone monolayer formation. The calculated data showed that locally the amorphous surface displayed very favorable topology for benzophenone adsorption in which both van der Waals and electrostatic interactions were maximized. After fulfillment of these optimal sites, the amorphous surface behaves like the crystalline surfaces for which the adsorption sites are nonspecific. Finally, the interface between cellulose/benzophenone monolayer and water was studied by molecular dynamics. The density profiles showed that the benzophenone molecules penetrated the amorphous phase while they remained at the surface in the crystalline models.

The xyloglucan–cellulose assembly at the atomic scale

“…44 The overall morphology of the microfibril was complex as it exposed the different crystalline surfaces that were previously recognized as important in the adsorption process of aromatic molecules. 20,32,33 The cellulose microfibril fragment together with its XG satellites was placed in a rectangular cell subjected to periodic boundary conditions with dimensions a ¼ 100 Å , b ¼ 100 Å , and c ¼ 42.154 Å . To model infinite chain length, the two border glucose residues of each cellulose chain were covalently bonded across the periodic box in the direction of the chain axis.…”

“…In fact, microfibril surfaces have various distinct topologies and consequently different physicochemical properties, which probably influence adsorption of other molecules. 20 Is there a highly specific site that repeats in space along the microfibril? If so, then the question of its location is of crucial importance.…”

“…20,[31][32][33] Our proposed models have the following features: (a) both partner molecules (cellulose fiber and XG in the present study) are explicitly present in the simulation medium; (b) interacting surface chains of cellulose and XG molecules are flexible; (c) no assumption is made about the organization of the complex, the two molecular axes do not need to be aligned; (d) the cellulose microfibril has (110), (1)(2)(3)(4)(5)(6)(7)(8)(9)(10), (010), and (100) crystal faces in realistic proportions; (e) we use periodic boundary conditions together with covalent links across the primitive cell, allowing us to model an infinite long cellulose fiber (in the direction of fiber axis) without end effects; (f) the procedure uses secondgeneration empirical force fields together with molecular dynamics for sampling the best geometries for the complex, conceptually the method of choice.…”

Modelling of Congo red adsorption on the hydrophobic surface of cellulose using molecular dynamics

“…These authors, however, did not consider the possibility of adsorption on the hydrophobic face of cellulose. In our continuing interest in modelling the surface interactions of cellulose with hydrophobic and hydrophilic chemicals (Mazeau and Vergelati 2002;Mazeau and Rivet 2008;Da Silva Perez et al 2004), this work was therefore devised to see whether stable interactions of CR on hydrophobic planes could also be found, using molecular dynamics simulations.…”

Molecular dynamics simulations of a guaiacyl β‐O‐4 lignin model compound: Examination of intramolecular hydrogen bonding and conformational flexibility

“…Surprisingly, very few computational studies have concerned lignin or lignocellulosic structures and their interactions. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Within a broad program dedicated to the study of wood cell wall polymers, we have undertaken a molecular modeling study of the three-dimensional characteristics of lignin. However, in regard to the complexity of the lignin network, it has appeared necessary to adopt a step-by-step approach.…”