Vesicle-polymer hybrid architectures: A full account of the parachute architecture

We have previously reported that polymerization of styrene in dioctadecyldimethylammonium bromide (DODAB) vesicles leads to so-called parachute-like morphologies where a polymer bead is attached to a vesicle. To learn the constructive principles of these novel polymer colloids, we present here a full characterization study. The dual nature of these particles, combining intrinsic Vesicle features with polymer colloid properties, requires characterization methods that address both the morphology (cryo-TEM, AFM, DLS) and the typical Vesicle characteristics (micro-DSC, fluorescence techniques, surfactant lysis). It is found that the vesicle characteristics after polymerization are virtually unchanged when compared to the bare vesicles. This observation can be fully accounted for by the putative complete phase separation between polymer and surfactant bilayer matrix. Several methods to release the polymer bead from its parental vesicle are presented. In a second part we investigate the relation between polymerization reaction conditions (i.e., temperature, mode of initiation, molecular weight of the polymer) and the resulting vesicle-polymer hybrid morphology. Unexpectedly, slight modifications in the reaction conditions prove to exert great influence on the produced morphology, resulting in novel vesicle-polymer architectures. It turns out that these variations in morphology are governed by intrinsic vesicle properties. As a general phenomenon, we find that polymerization of styrene in DODAB vesicles-independent of process parameters-inevitably leads to microphase separation between the amphiphilic bilayer matrix and polymer.