New Vesicle−Polymer Hybrids:  The Parachute Architecture

Abstract

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.

A Topology Map for Novel Vesicle-Polymer Hybrid Architectures

“…The vesicle±polymer products are analyzed by cryo-transmission electron microscopy (cryo-TEM), which proved a powerful tool to study these structures since it visualizes ultra-structural details of both the polymer and the vesicle. [9] On the basis of our results, we conclude that the nanoscopic phase separation between surfactant matrix and polymer generally occurs for all common surfactant/polymer combinations. The individual morphology, however, depends on the specific interplay between vesicle-matrix and polymer.…”

“…Polymer shell structures are claimed by several research groups for diverse vesicle and polymer combinations. [3±8] In contrast, we have previously found that the polymerization of styrene in dioctadecyldimethylammonium bromide (DODAB) vesicles results in parachute-like morphologies [9] due to complete phase separation between the polymer and the vesicle-bilayer matrix. Additionally, we were able to demonstrate that the phase separation phenomenon in this particular system (DODAB vesicles and polystyrene) is largely independent of process parameters like the molecular weight of the polymer, the initiating chemistry and the polymerization temperature.…”

Polymer Particles by Templating of Vesicles

“…[14] However, it was only very recently that the structure of the polymer itself could successfully be visualized. While in a dioctadecyldimethylammonium bromide/polystyrene system cryogenic transmission electron microscopy investigations clearly show that a phase separation occurs, leading to a parachute-like structure, [15] in a similar dioctadecyldimethylammonium chloride/alkylmethacrylate mixture confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) investigations provide evidence for a homogeneously closed polymer hollow sphere morphology. [16] The differences between the two systems perhaps arise from the fact that the alkyl chain milieu within the bilayer is a poor solvent for polystyrene while the poly(alkylmethacrylate)s have a better compatibility.…”

“…Another point may concern the relative monomer concentrations: while the alkylmethacrylates in one investigation [16] were applied in a molar ratio of lipid to monomer that was smaller than 1:1, in another, using styrene, [15] this ratio was 1:2. A similar phase separation within the bilayer, leading to morphologies analogous to those reported by Jung et al, [15] has been observed upon solubilization of large amounts of toluene (up to a lipid-to-toluene ratio of »1:4) in dipalmitoylphosphatidylcholine vesicles. [17] As already mentioned before, one essential feature of the templating process is that the newly formed polymer has to be able to retain the characteristics of its template even after its isolation.…”

Chemistry in block copolymer nanocontainers : self-assembly, container properties and confined enzymatic reactions

“…48 A similar concept uses just the "skeleton" of the vesicular aggregates as a template. [49][50][51][52][53][54][55][56] 55,57 In this case the amphiphilic molecules just provide a geometrically restricted environment for dissolving and polymerizing conventional monomers. It is well known that vesicles or liposomes are able to solubilize hydrophobic substances to a certain degree.…”