Molecular dynamic simulations of polyacrylonitrile in ethanol and water solvents

For some decades Polyacrylonitrile (PAN) fibers have been calling the attention of many researchers due to a large application of this polymer in several areas of science and industry. However, its structural characterization in different solvents is unclear. Thus, we have used molecular dynamic simulations to study the PAN in ethanol and water solvents. Our dihedral analysis show that the trans/gauche ratio is ∼25% lower than in solid state experiments, which can be attributed to the solvent effects in the PAN structure. From the radius of gyration analysis, our results show the PAN adopts a folded and unfolded conformation in ethanol and water solvents, respectively. The folded form is stabilized by the nitrogen-nitrogen intramolecular interaction, with two maximum peaks in the radial distribution function (RDF): one in 0.35 nm and the second in 0.60 nm. In addition, the –CH2 group from PAN is stabilized by the –CH3 group from the ethanol molecules. The results presented here provide new insight into the PAN structure, and our results are in agreement with experimental data.