Silica‐coated vesicles have been produced by the deposition of silica onto unilamellar vesicles from aqueous solution for the first time. The quaternary ammonium surface of the surfactant vesicles is receptive to silica and facilitates deposition of up to 5–10 nm of it. The “petrified” vesicles are stable to dehydration and can be visualized by conventional TEM (see Figure) without additional staining agents.

The influence of organized media on polymerization reactions results in many cases in interesting morphologies of the polymeric material. In the present study, vesicle bilayers were used as ordered medium for the free radical polymerization of styrene. Cryo-electron microscopy gives evidence that the polymerization induces phase-separation phenomena leading to parachute-like morphologies. On the basis of general knowledge about vesicles and polymerizations in heterogeneous media, explanations for the observed phenomena are given. Bearing in mind that vesicles are outstanding models for membrane mimetic chemistry, it becomes evident that these findings can be relevant to the investigation of, for example, membrane-protein interactions.

The solubilization of styrene in large unilamellar DODAB vesicles is investigated at a styrene to DODAB molar ratio of 2:1. The combination of various vesicle characterization methods allows a simultaneous look at vesicle morphology (cryo-TEM, DLS) and molecular interactions (micro-DSC, various fluorescence techniques) and gives a complete picture of the DODAB vesicles before and after the addition of styrene. Cryo-TEM and DLS results reveal that the addition of styrene does not break up the DODAB vesicles as an entity, but the peculiar angular DODAB vesicle morphology becomes smoother and the geometries tend to be more curved. The change in morphology is explained by an enhanced bilayer fluidity and the drastic depression of the phase transition temperature as determined from calorimetry and fluorescence experiments. Moreover, micro-DSC scans and fluorescence experiments with two different pyrene probes suggest a nonhomogeneous distribution and partial demixing of solute and bilayer for temperatures below ∼27 °C. Above this temperature, the solute appears uniformly distributed and facilitates molecular motion in the amphiphile aggregate. The diffusion coefficient for the lateral diffusion of an amphiphilic probe is then increased by a factor of 2 compared to the pure DODAB vesicles. The observed solubilization phenomena are rationalized by interactions of the solute with both the hydrocarbon part and the polar headgroup region of the bilayer.

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.