Tuning the aggregation performance by varying the substituent position: comparative study of neutral bis-urea derivatives in aqueous medium

Abstract

A set of three neutral bis-urea derivatives has been purposefully chosen to investigate the consequences of positional isomers on the aggregation performance. The comparative analysis based on the spectral study proved that all three isomers 1, 2 and 3 exhibit substantial aggregation behavior while compound 2 is more potent in the formation and stabilization of aggregates. Variation in the aromatic core changes the directional property and steric effect, which causes diversity in the morphology of aggregated species of 1, 2 and 3, and this is further validated by FESEM images and a theoretical approach. Additional studies were also conducted to assess the influence of temperature, salt (NaCl), urea and pH on the aggregation properties to gain a deeper understanding of the relative aggregation aptitude and the results indicate the strong hydrogen bonding responsible for the aggregation phenomenon.