Equilibrium Chain Exchange Kinetics of Diblock Copolymer Micelles:  Tuning and Logarithmic Relaxation

Lund, Reidar; Willner, Lutz; Richter, D.; Dormidontova, Elena E.

doi:10.1021/ma060328y

Cited by 162 publications

(297 citation statements)

References 39 publications

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“…In contrast, the exchange rate is significantly faster at higher temperatures. These results resemble observations on self-assembled polymeric micelles, in which monomer expulsion and insertion is the rate-determining step of system dynamics (20,21). Moreover, monomer polymerization and depolymerization are reported to be the main exchange mechanism of supramolecular polymers in organic solvents (22).…”

Section: Resultssupporting

confidence: 82%

Spatiotemporal control and superselectivity in supramolecular polymers using multivalency

Albertazzi

Martínez-Veracoechea

Leenders

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

116

171

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Multivalency has an important but poorly understood role in molecular self-organization. We present the noncovalent synthesis of a multicomponent supramolecular polymer in which chemically distinct monomers spontaneously coassemble into a dynamic, functional structure. We show that a multivalent recruiter is able to bind selectively to one subset of monomers (receptors) and trigger their clustering along the self-assembled polymer, behavior that mimics raft formation in cell membranes. This phenomenon is reversible and affords spatiotemporal control over the monomer distribution inside the supramolecular polymer by superselective binding of single-strand DNA to positively charged receptors. Our findings reveal the pivotal role of multivalency in enabling structural order and nonlinear recognition in watersoluble supramolecular polymers, and it offers a design principle for functional, structurally defined supramolecular architectures.self-assembly | simulations | energy transfer O ne of the most fascinating features of living matter is the precise control over biological activity in space and time.The cell membrane provides a remarkable example of such highfidelity spatiotemporal control in a complex biological setting, wherein thousands of different components, namely lipids and proteins, self-assemble into a 2D fluid mosaic (1). To perform the functions that the cell requires, lipids and proteins are heterogeneously distributed and specific biomolecules are segregated in active nanometer-sized domains often referred to as rafts (2). This distribution is highly dynamic, such that these platforms can be rapidly assembled and disassembled (3). The principles that underlie control over the molecular composition of the cellular microenvironment in space and time are the subject of great scientific debate as they are of crucial importance for cell functioning, signaling, growth, and division (4).One of the main goals of supramolecular chemistry is the noncovalent synthesis of functional molecular architectures through weak and reversible interactions (5). In this framework, a key challenge is the design of molecular building blocks that are able to self-organize hierarchically and in a cooperative fashion (6), thus mimicking the dynamic and structural complexity of living systems as well as their functionality. Various modular multicomponent systems have been successfully developed (7), but the spatiotemporal control of the localization of distinct components within synthetic supramolecular assemblies has yet to be realized. Mastering the spatial distribution of assembled molecules in a noncovalent synthesis is as crucial for their functionality as regio-selectivity impacts the molecular properties of organic molecules synthesized in a classical covalent manner. An interesting supramolecular polymer, where multiple components coassemble cooperatively in water, is based on 1,3,5-benzenetricarboxamide derivatives (BTAs) (8).Of particular relevance for the present work, is the fact that reversible interactions between ...

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Section: Resultssupporting

confidence: 82%

Spatiotemporal control and superselectivity in supramolecular polymers using multivalency

Albertazzi

Martínez-Veracoechea

Leenders

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

116

171

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“…DOI: 10.1103/PhysRevLett.102.188301 PACS numbers: 82.35.Jk, 61.05.cf, 82.35.Lr, 82.70.Uv An archetypical example and a model system for self assembly is the family of amphiphilic A-B diblock copolymers that undergo micellization in aqueous solutions [1,2]. In such systems where the interfacial energy is usually large, the structure formation may be influenced by prominent kinetic barriers leading to a variety of trapped metastable states unable to reach their global equilibrium [3][4][5][6][7][8]. Despite recent progress on manipulation of nonequilibrium structures via kinetic control, such as by sophisticated mixing protocols [6,9,10], a complete understanding of the physical mechanisms of the self-assembly process is still lacking.…”

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confidence: 99%

“…Extensive previous studies have shown that these asymmetric PEP-PEO diblock copolymers form well-defined starlike micelles in water-dimethylformamide (DMF) solvent mixtures [7,8,21,22]. This solvent pair provides a strong selectivity for PEO; however, since water and DMF have very different interfacial tensions towards the insoluble PEP block ( % 46 and 8 mN=m respectively) [21], the interfacial energy can be easily tuned by varying the composition.…”

mentioning

confidence: 99%

“…This solvent pair provides a strong selectivity for PEO; however, since water and DMF have very different interfacial tensions towards the insoluble PEP block ( % 46 and 8 mN=m respectively) [21], the interfacial energy can be easily tuned by varying the composition. This tuning parameter intimately controls equilibrium unimer exchange rates [7,8]. Very importantly, in pure DMF only single chains (unimers) are present; but as soon as some water is added, the block copolymers spontaneously aggregate into micelles.…”

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confidence: 99%

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Structural Observation and Kinetic Pathway in the Formation of Polymeric Micelles

et al. 2009

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The route by which amphiphilic molecules self-assemble into micelles is still not fully understood. In this Letter, we present direct structural information on the birth and growth of block copolymer micelles by means of synchrotron x-ray scattering with millisecond time resolution. Using a quantitative model, we show that the self-assembly process can be viewed as a nucleation and growth type process where the elemental growth mechanism is an exchange of single molecules. DOI: 10.1103/PhysRevLett.102.188301 PACS numbers: 82.35.Jk, 61.05.cf, 82.35.Lr, 82.70.Uv An archetypical example and a model system for self assembly is the family of amphiphilic A-B diblock copolymers that undergo micellization in aqueous solutions [1,2]. In such systems where the interfacial energy is usually large, the structure formation may be influenced by prominent kinetic barriers leading to a variety of trapped metastable states unable to reach their global equilibrium [3][4][5][6][7][8]. Despite recent progress on manipulation of nonequilibrium structures via kinetic control, such as by sophisticated mixing protocols [6,9,10], a complete understanding of the physical mechanisms of the self-assembly process is still lacking. Therefore, a more fundamental approach to control and design such nanostructures is still a very challenging task.Concerning micellization kinetics in particular, theories predict various growth mechanisms. Some theories exclusively favor the classical Aniansson-Wall mechanism [11]-a step-by-step insertion mechanism of single molecules (unimers) [3,[12][13][14], while others emphasize the role of fragmentation or recombination mechanisms, i.e., fusion and fission of individual micellar entities [15,16]. Experimentally, appropriate data are scarce to find and what do exist are indirect in the sense that the structural evolution is not probed [17][18][19][20]. This is primarily due to the lack of experimental techniques having the correct spatial and temporal resolution with the combination of a suitable well-defined model system. In addition, there is a prominent lack of detailed physical modeling of the data. Thus, so far, results remain largely inconclusive.Here we show that the required nanoscale spatial and millisecond temporal resolution for an in situ investigation of micellization can be reached by using synchrotron x-ray scattering. The self-assembly process of a model amphiphilic block copolymer was triggered by an interfacial tension jump experiment by rapidly changing the solvent quality for one of the blocks. Using a detailed quantitative model, we further demonstrate that the kinetic pathway proceeds by unimer exchange where only single chains are added or removed at a time.As a model system, we employ a well-defined amphiphilic poly(ethylene-alt-propylene)-poly(ethylene oxide) (PEP1-PEO20, numbers indicate the approximate molecular weight in kg=mole) block copolymer [21]. Extensive previous studies have shown that these asymmetric PEP-PEO diblock copolymers form well-defined starlike micelles in w...

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“…Relatively polar copolymers and surfactants that readily dissolve in water form rather dynamic micelles with unimeric exchange rates up to the microsecond time scale [29,30]. Encapsulated compounds in such micelles will also be released rapidly because usage as drug delivery systems is always accompanied with significant dilution.…”

Section: Introductionmentioning

confidence: 99%

Controlled block copolymer micelle formation for encapsulation of hydrophobic ingredients

et al. 2013

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Abstract. We report on the formation of polymeric micelles in water using triblock copolymers with a polyethylene glycol middle block and various hydrophobic outer blocks prepared with the precipitation method. We form micelles in a reproducible manner with a narrow size distribution. This suggests that during the formation of the micelles the system had time to form micelles under close-to-thermodynamic control. This may explain why it is possible to use an equilibrium self-consistent field theory to predict the hydrodynamic size and the loading capacity of the micelles in accordance with experimental finding. Yet, the micelles are structurally quenched as concluded from the observation of size stability in time. We demonstrate that our approach enables to prepare rather hydrophobic block copolymer micelles with tunable size and loading.

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Equilibrium Chain Exchange Kinetics of Diblock Copolymer Micelles: Tuning and Logarithmic Relaxation

Cited by 162 publications

References 39 publications

Spatiotemporal control and superselectivity in supramolecular polymers using multivalency

Spatiotemporal control and superselectivity in supramolecular polymers using multivalency

Structural Observation and Kinetic Pathway in the Formation of Polymeric Micelles

Controlled block copolymer micelle formation for encapsulation of hydrophobic ingredients

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