From vesicles to micelles: microphase separation of amphiphilic dendrimer copolymers in a selective solvent

Abstract

The microphase separation of amphiphilic dendrimer copolymers in a selective solvent with different excluded volume effects (α_S) is investigated using three-dimensional real space self-consistent field theory. The morphological transition of disorder-to-order and order-to-order is observed by systematically regulating the excluded volume effect parameter, interaction parameter of block species, and the spacer length of the second generation of the dendrimer. The ordered segregates of the dendrimer solution are observed with a stronger excluded volume effect due to the strong depletion effect of solvent on the dendrimer. The relative magnitude between hydrophobic block B and hydrophilic block C is very important for microphase separation: when they are equal (N_B = N_C), a structural shift from vesicles to micelles has been found upon increasing the interaction parameter, and the region of disordered morphology is controlled by the interfacial free energy (U_int); when N_B > N_C, the vesicular morphologies overwhelmingly appear in the ordered region and then N_C increases to close to N_B, and the ordered aggregates take a shift from vesicles to micelles. Furthermore, the amphiphilic block C of the dendrimer is intended to enlarge to N_C > N_B, the micellar morphology is dominant in the ordered regime with a stronger excluded volume effect, which contributes to the decrease in the hydrophobic block repulsion that is affected by the decrease in the entropic free energy (−TS). The knowledge obtained from the microphase separation of dendrimer solution induced by the excluded volume effect of selective solvent is full of referential significance in understanding the morphological transition from vesicles to micelles for the amphiphile in the field of soft matter.