Free radical polymerization of styrene in dioctadecyldimethylammonium bromide vesicles

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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“…Attention has been focused on the unusual electronic [2,3] and mechanical [4,5] properties predicted for these materials.…”

Section: Methodsmentioning

confidence: 99%

A Topology Map for Novel Vesicle-Polymer Hybrid Architectures

et al. 2000

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“…No separate monomer phase could be detected and the vesicle dimensions remained constant within experimental accuracy during the swelling and subsequent polymerization. [8,9] From this it was concluded that the polymerization really occurred in the interior of the bilayer and under retention of the vesicle structure. Kinetic studies on a similar system revealed that the free-radical polymerization (of alkylacrylates) in vesicles is a very fast reaction: [10] the monomers are present locally, within the bilayer, at a rather high concentration and, perhaps, also have a favorable orientation for the chain reaction.…”

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confidence: 97%

“…Therefore, their lateral mobility, the phase behavior, and even the permeability of such membranes have been found to be not significantly changed by the presence of the polymer. [8,9] An interesting possibility for studying the properties of these polymer-stabilized membranes in more detail is to use planar lipid bilayers, so-called black lipid membranes (BLMs), as model systems.…”

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confidence: 99%

Polymer Particles by Templating of Vesicles

Hotz¹,

Meier

1998

Adv. Mater.

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Template‐directed synthesis is an elegant approach to defined nanostructured materials. Vesicles or liposomes have already been used in the synthesis of small inorganic particles, but their use as a template for polymer synthesis is rare. Despite this, direct templating of vesicles offers interesting new possibilities for the formation of defined nanostructured polymers. While the polymer morphology is determined by the size and shape of the templates, the polymer framework can be modified by conventional chemical reactions. The authors envisage applications in separation processes or drug delivery.

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“…Successful intrabilayer swelling of vesicles with hydrophobic monomers and subsequent radical polymerization have been reported. [16][17][18][19][20] temperatures. These studies indicate that rearrangement of the amphiphilic molecules is possible and brought on by phase separation upon swelling which leads us to believe that more drastic morphological transformations of (polymer) vesicles can be induced.…”

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Morphological transitions in polymer vesicles upon bilayer swelling with small hydrophobic molecules in water

et al. 2013

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We show that when unilamellar polymer vesicles dispersed in water made from a blockcopolymer, in this case poly((ethylene oxide)45-block-(methyl methacrylate)164), poly((ethylene oxide)45-block-(methyl methacrylate)170), or poly(n-butyl methacrylate)81-block-(2-(dimethylamino)ethyl methacrylate)20, are exposed to small hydrophobic molecules, here methyl methacrylate as well as n-butyl methacrylate, they can undergo morphological transitions. Upon swelling, the polymersomes lose their original simple bilayer morphology and transform into more complex coil-like and patchy colloidal structures, as investigated experimentally by cryogenic electron microscopy (cryo-EM). Dissipative particle dynamics (DPD) simulations on a model flat bilayer indeed show that transitions can occur upon bilayer swelling, which is accompanied by a change in the mechanical bilayer properties. The transition involves the formation of water pockets in the interior regions of the bilayer. Co-existence of the various morphologies in the experiments suggests an activation barrier towards morphological changes and a possibility of multiple meta-stable states. The latter indeed is supported by the existence of multiple minima in the surface tension as a function of bilayer area, as found in the simulations

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Free radical polymerization of styrene in dioctadecyldimethylammonium bromide vesicles

Cited by 61 publications

References 19 publications

A Topology Map for Novel Vesicle-Polymer Hybrid Architectures

A Topology Map for Novel Vesicle-Polymer Hybrid Architectures

Polymer Particles by Templating of Vesicles

Morphological transitions in polymer vesicles upon bilayer swelling with small hydrophobic molecules in water

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