title: Role of Naphthenic Acids in Controlling Self-Aggregation of a Polyaromatic Compound in Toluene.
abstract: In this work, a series of molecular dynamics simulations were performed to investigate the effect of naphthenic acids (NAs) in early stage self-assembly of polyaromatic (PA) molecules in toluene. By exploiting NA molecules of the same polar functional group but different aliphatic/cycloaliphatic nonpolar tails, it was found that irrespective of the presence of the NA molecules in the system, the dominant mode of π-π stacking is a twisted, offset parallel stacking of a slightly larger overlapping area. Unlike large NA molecules, the presence of small NA molecules enhanced the number of π-π stacked PA molecules by suppressing the hydrogen bonding interactions among the PA molecules. Smaller NA molecules were found to have a higher tendency to associate with PA molecules than larger NA molecules. Moreover, the size and distribution of π-π stacking structures were affected to different degrees by changing the size and structural features of the NA molecules in the system. It was further revealed that the association between NA and PA molecules, mainly through hydrogen bonding, creates a favorable local environment for the overlap of PA cores (i.e., π-π stacking growth) by depressing the hydrogen bonding between PA molecules, which results in the removal of some toluene molecules from the vicinity of the PA molecules.
authors.forename: Robel B
authors.initials: RB
authors.lastname: Teklebrhan
authors.forename: Cuiying
authors.initials: C
authors.lastname: Jian
authors.forename: Phillip
authors.initials: P
authors.lastname: Choi
authors.affiliation: Institute of Nuclear and New Energy Resources, Tsinghua University , Beijing 100084, China.
authors.forename: Zhenghe
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Department of Chemical Engineering, Ugelstad Laboratory, Norwegian University of Science and Technology (NTNU) , Trondheim NO 7491, Norway.
authors.forename: Johan
authors.initials: J
authors.lastname: Sjöblom