Molecular Modeling of the Solvent Structuring of Chloroform around Cellulose Triacetate

A molecular dynamics simulation of the hexamer units of cellulose triacetate (CTA) in chloroform was performed to investigate the solvent structuring and dynamics behavior of chloroform molecules around the CTA polymer. During the simulation, a large fluctuation in the main chain conformation of CTA was observed in this solvent. Moreover, ring puckering of the glucose unit was also observed. In order to investigate the solvent structuring of chloroform around the solute molecule, the site-specified radial distribution function and the average velocity of the solvent atoms were precisely analyzed as a function of the distance from the CTA site. The results were compared with that obtained in our previous simulation of CTA in DMSO. The comparison showed that some DMSO molecules were strongly attracted by CTA sites, such as acetyl methyl residue, while the chloroform molecules were weakly attracted by the carbonyl oxygen of CTA. These differences affect the stability of the conformation of CTA in different solvents. In chloroform, the conformation of acetyl residues, especially at the 6 position, were rotating widely in every monomer unit, which caused a large fluctuation on the main-chain conformation. On the other hand, all acetyl side chains maintained a stable conformation in DMSO because of the strong association of DMSO molecules to the acetyl residue of CTA. The role of the solvent effects on the conformation of the polymer in solution was considered at the molecular level in this work.