Study of the aggregation behaviour of three primary reactive dyes via molecular dynamics simulations

The aggregation behaviours of three primary reactive dyes in water were determined by molecular dynamics simulations. The aggregation equilibrium time period was determined by SASA analyses. The maximum aggregation sizes for the seven systems were not greater than that of a pentamer. For single dye solutions, the aggregation trend followed the order Y176 > B194 > R239. For two-colour mixed dye solutions, the aggregation compatibilities followed the order Y176-B194 > Y176-R239 > B194-R239. Overall, the three dyes had satisfactory aggregation compatibilities. The dye-dye and dye-water molecule interactions were analysed by RDG and aRDG methods. The results graphically showed the place, strength and type of the interactions. The main interactions between the dye anions were the VdW and π-π stacking interactions. Most parts of the dyes showed VdW interactions with water. The aggregation tendency may be affected by the number and the position of the water-soluble groups of the dyes, the molecular weight of the dye molecules and whether or not the configuration of the dyes was beneficial to the formation of π-π stacking interactions.