Molecular Modeling of the Solvent Structuring of DMSO around Cellulose Triacetate

Abstract

Abstract Molecular dynamics simulations of cellulose triacetate (CTA) were performed with explicit DMSO molecules in order to investigate the solvent structuring of DMSO around the CTA polymer. A hexamer unit of CTA was used as a model instead of polymer CTA. The molecular dynamics trajectory was started from a minimum conformation, which was found from an analysis of the adiabatic potential-energy surface obtained for glycosidic dihedral angles of φ and ψ. It showed that most of the time the trajectory stayed in their initial conformation in DMSO solvent. A distance analysis between the acetyl methyl residues of CTA showed that they are in good accordance with the NMR-NOESY data obtained by Tezuka.1 In order to elucidate the solvation structure of DMSO around the solute molecules, the site-specified radial distribution function, the orientation and the time courses of the DMSO movement were analyzed precisely. The results showed that some DMSO molecules strongly interact with CTA at specific sites, such as acetyl methyl residues and H1 ring protons. Moreover, it was found that those DMSO molecules frequently interact to CTA, not with one site, but with two or more sites simultaneously. These DMSO molecules would play an important role in the conformation of CTA in this solvent.