Helical transition and growth of supramolecular assemblies of chiral discotic molecules

It has recently been established experimentally that the supramolecular ass emblies formed by a particular class of chiral discotic molecules in soluti on exhibit a helical transition. To rationalize the experimental data, we a pply the standard theory of linear self-assembly modified by a simple two-s tate model for the molecules in the aggregates, based on the Zimm-Bragg the ory for the helical transition in conventional polymers. The theory provide s a description of the amount of material in aggregates as well as their me an size and state of helicity as a function of the concentration of dissolv ed material, two binding strengths, and a parameter measuring the cooperati vity of the helical transition. By fitting to the experimental data, all th e model parameters are determined. It emerges that the helical transition i s highly cooperative and that the growth spurt the aggregates exhibit at lo w temperatures is largely due to coupling of the self-assembly to the helic al transition.