A Topology Map for Novel Vesicle-Polymer Hybrid Architectures

Abstract

Templating polymerizations in surfactant phases have proved versatile approaches in polymer chemistry to access novel materials possessing order on the nanometer scale. [1,2] The concept is to direct the growth of either organic or inorganic polymer material into the desired preestablished structure of a given surfactant phase. Vesicles, among many other surfactant phases, have attracted considerable interest during the last years as particularly attractive templating phases.[3±10] The polymerization in vesicles comprises the free-radical polymerization of small oil-soluble monomers which are solubilized within the hydrophobic part of a vesicle matrix built by non-functional lipids. Currently, two different types of morphologies are reported to result from polymerization in vesicles: Closed spherical polymer shells and so-called parachute-like morphologies. 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.[11] It could, however, be argued that the expected morphology of polymerization reactions in vesicles would depend on the mutual miscibility of monomer/polymer and surfactant matrix. [3] To investigate the relationship between the chosen surfactant/polymer combination, the applied reaction conditions and the final vesicle±polymer morphology, we performed the present study using a wide variety of polymers and surfactants. 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. Finally, exploiting this knowledge, we present here constructive guidelines for the synthesis of novel vesicle±polymer hybrid architectures. In a first set of experiments, we kept the vesicle-forming amphiphile (DODAB) constant and varied the monomer(s). We have earlier described that the polymerization of styrene in DODAB vesicles leads either to the so-called parachute or to the related Matrioshka architecture, depending on the initiator type. Assuming in the first place that the polymer separates from the bilayer matrix by polymer diffusion, one could attempt to immobilize the pol...

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“…Recently, DODAB vesicles were used as templates for growing silica from tetraethylortosilicate or tetramethylortosilicate so that petrified vesicles were obtained [81]. Also, monomers, such as styrene, isoprene, and others, were readily solubilized inside the vesicle bilayer and used to form vesicle-polymer hybrids upon initiator induced polymerization [82].…”

Interface Engineering in Multiphase Systems toward Synthetic Cells and Organelles: From Soft Matter Fundamentals to Biomedical Applications

“…Stable lipid domains in copolymer vesicular membrane can be obtained by carefully tuning the composition of heterogeneous membrane. [44,46,158,160,163,175,176,178] To expedite trafficking of ions and small molecules across the membrane, ionophores, ion channels and ATPases are integrated in the vesicular membrane (Figure 9a-d). [124,132,163,[261][262][263][264][265][266] These biomacromolecules have been successfully incorporated into vascular membranes of lipids, copolymers and lipidcopolymer hybrids.…”

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“…While polymerization of alkyl (meth)acrylates in dioctadecyl-ammonium chloride vesicles [42,43] or the reaction of lipofullerenes in dipalmitoyl-phosphatidylcholine vesicles [44] clearly leads to the formation of polymer hollow spheres, in the case of styrene/divinylbenzene in dioctadecylammonium bromide vesicles an intravesicular phase separation occurs during polymerization, thus leading to the formation of so-called parachute-like structures [41,47].…”