Shear-Induced Formation of Multilamellar Vesicles (“Onions”) in Block Copolymers

Zipfel, J.; Lindner, Peter; Tsianou, Marina; Alexandridis, Paschalis; Richtering, Walter

doi:10.1021/la981666y

Cited by 120 publications

(90 citation statements)

References 30 publications

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“…Experiments on a variety of systems which differ significantly in their microscopic details show nevertheless striking similarities in their macroscopic behavior under shear. The systems under investigation include block copolymers [1,2,3,4,5,6], low molecular weight (LMW) liquid crystals [7,8,9], lyotropic lamellar phases (both LMW [10,11,12] and polymeric [13]), and liquid crystalline side-chain polymers [14,15]. These experiments use either a steady shear (typically for the low viscosity systems e.g.…”

Section: Introductionmentioning

confidence: 99%

Shear-induced instabilities in layered liquids

2002

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Motivated by the experimentally observed shear-induced destabilization and reorientation of smectic A like systems, we consider an extended formulation of smectic A hydrodynamics. We include both, the smectic layering (via the layer displacement u and the layer normalp) and the director n of the underlying nematic order in our macroscopic hydrodynamic description and allow both directions to differ in non equilibrium situations. In an homeotropically aligned sample the nematic director does couple to an applied simple shear, whereas the smectic layering stays unchanged. This difference leads to a finite (but usually small) angle betweenn andp, which we find to be equivalent to an effective dilatation of the layers. This effective dilatation leads, above a certain threshold, to an undulation instability of the layers. We generalize our earlier approach [Rheol. Acta 39 (3), 15] and include the cross couplings with the velocity field and the order parameters for orientational and positional order and show how the order parameters interact with the undulation instability. We explore the influence of various material parameters on the instability. Comparing our results to recent experiments and molecular dynamic simulations, we find a good qualitative agreement.

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Section: Introductionmentioning

confidence: 99%

Shear-induced instabilities in layered liquids

2002

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“…[25] For block copolymer EO 20 PO 70 EO 20 with a relatively longer hydrophilic chain, only multilamellar polymer vesicles were observed. [26] Until now, there has been no report that this block copolymer may form unilamellar vesicular structures. We propose that in our experiments, the polymer/siliceous composites cooperatively assemble into organized shapes at different temperatures similar to the structure evolution in dilute block-copolymer solutions.…”

Section: Full Papermentioning

confidence: 99%

Siliceous Unilamellar Vesicles and Foams by Using Block‐Copolymer Cooperative Vesicle Templating

Wang

Zhou

et al. 2007

Adv Funct Materials

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By employing commercial poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) block copolymers as templates in near‐neutral aqueous solutions in the absence of organic cosolvents, unilamellar siliceous vesicles and nanofoams with ultrahigh pore volumes (> 3 cm3 g–1) are successfully synthesized. At controlled pH, a tubular micelle → unilamellar vesicle → nanofoam structural transformation is observed by increasing the reaction temperature. It is proposed that the siliceous vesicles are synthesized via a co‐operative block‐copolymer vesicle templating approach, while the siliceous nanofoams are obtained by the fusion of vesicles at increased ionic strength. Compared to literature methods to synthesize siliceous vesicles and foams, our method is convenient, cheap, and produces a high yield. Siliceous nanofoams synthesized by using our approach show superior bioimmobilization capacity over other porous materials for biomolecules with large molecular weight.

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“…Schillen et al 70 100 ) copolymers in butanol/water systems. 71,72 Valentini et al 73 formed 15-250 nm vesicles from poly(propylene sulfide)-block-poly(ethylene glycol). They were able to determine the border between the hydrophobic and hydrophilic junctions in the polymeric vesicles with various NMR techniques, this being important for pinpointing water penetration.…”

Section: Copolymer Systems Producing Vesiclesmentioning

confidence: 99%

Preparation of block copolymer vesicles in solution

Soo

Eisenberg

2004

J Polym Sci B Polym Phys

366

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Block copolymer vesicles can be prepared in solution from a variety of different amphiphilic systems. Polystyreneblock-poly(acrylic acid), polystyrene-block-poly(ethylene oxide), and many other block copolymer systems can produce vesicles of a wide range of sizes; those in the range of 100 -1000 nm have been explored extensively. Different factors, such as the absolute and relative block lengths, the presence of additives (ions, homopolymers, and surfactants), the water content in the solvent mixture, the nature and composition of the solvent, the temperature, and the polydispersity of the hydrophilic block, provide control over the types of vesicles produced. Their high stability, resistance to many external stimuli, and ability to package both hydrophilic and hydrophobic compounds make them excellent candidates for use in the medical, pharmaceutical, and environmental fields.

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Shear-Induced Formation of Multilamellar Vesicles (“Onions”) in Block Copolymers

Cited by 120 publications

References 30 publications

Shear-induced instabilities in layered liquids

Shear-induced instabilities in layered liquids

Siliceous Unilamellar Vesicles and Foams by Using Block‐Copolymer Cooperative Vesicle Templating

Preparation of block copolymer vesicles in solution

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