Flow Effects in Supramolecular Chirality

There are an increasing number of reports on the emergence of circular dichroic signals when solutions of J‐aggregates are vortex‐stirred. Some authors claim that the transfer of chirality from the macroscopic stirring vortex occurs at the level of electronic transitions. Others argue that the signal observed is not due to true circular dichroism (CD), but rather that it is an artifact due to combinations of linear polarization contributions. For both interpretations it is necessary to assume that the alignment by effect of flows dominates over the Brownian dynamics. Therefore, the topic belongs to supramolecular chemistry because the alignment in current flows can only occur for relatively large particles with an appropriate shape. The phenomenon is detected by CD spectroscopy, which itself is also the main hindrance, even controversial, in its study and interpretation. However, modern Mueller matrix polarimetry can solve some of the problems. The phenomenon has been explained using different scenarios; however, in some of the systems the experimental evidence only supports the model in which deformation (folding/torsion) of elastic soft‐matter yields true CD. Here we discuss the role of the gradient of shear rates in the deformation of nano particles of soft matter to give chiral supramolecular structures, as the first step to explaining the phenomenon.