Minimum free-energy paths for the self-organization of polymer brushes

Gleria, Ignacio; Mocskos, Esteban; Tagliazucchi, Mario

doi:10.1039/c6sm02725c

Cited by 7 publications

(9 citation statements)

References 59 publications

(83 reference statements)

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“…Metastable structures cannot be described by the theory reported in this work, but it may be possible to study transitions between them in the future using the recently reported molecular theory/string method formalism. 45 The theory predicts the occurrence of a micelle→fiber→lamella transition when the size of the tail or linker blocks is increased, which is in qualitative agreement with experimental results for peptide amphiphiles [14][15][16][17] and long diblock copolymers. 38 This prediction is also consistent with Israelachvili's packing theory, 30,31 as we showed by calculating the packing parameter of Israelachvili's theory using our theory.…”

Section: Discussionsupporting

confidence: 82%

Self-assembly of model short triblock amphiphiles in dilute solution

et al. 2018

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In this work, a molecular theory is used to study the self-assembly of short diblock and triblock amphiphiles, with head-tail and head-linker-tail structures, respectively. The theory was used to systematically explore the effects of the molecular architecture and the affinity of the solvent for the linker and tail blocks on the relative stability of the different nanostructures formed by the amphiphiles in dilute solution, which include spherical micelles, cylindrical fibers and planar lamellas. Moreover, the theory predicts that each of these nanostructures can adopt two different types of internal organization: (i) normal nanostructures with a core composed of tail segments and a corona composed of head segments, and (ii) nanostructures with a core formed by linker segments and a corona formed by tail and head segments. The theory predicts the occurrence of a transition from micelle to fiber to lamella when increasing the length of the tail or the linker blocks, which is in qualitative agreement with the geometric packing theory and with experiments in the literature. The theory also predicts a transition from micelle to fiber to lamella as the affinity of the solvent for the tail or linker block is decreased. This result is also in qualitative agreement with experiments in the literature but cannot be explained in terms of the geometric packing theory. The molecular theory provides an explanation for this result in terms of the competition between solvophobic attractions among segments in the core and steric repulsions between segments in the corona for the different types of self-assembled nanostructures.

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Section: Discussionsupporting

confidence: 82%

Self-assembly of model short triblock amphiphiles in dilute solution

et al. 2018

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“…There is a free energy barrier expected between the two phases and the diblock copolymer nanogate could stay in a metastable state for a time scale that depends on the height of the energy barrier. For neutral homopolymer brushes grafted on flat surfaces, such a free energy barrier has been recently demonstrated by Gleria et al using a molecular theory combined with the improved string method . In this present study, we test the stabilities of the two phases at varying pHs and are able to estimate the boundaries of pH window for the coexistence as shown in Figure B.…”

Section: Resultsmentioning

confidence: 53%

“…For neutral homopolymer brushes grafted on flat surfaces, such a free energy barrier has been recently demonstrated by Gleria et al using a molecular theory combined with the improved string method. 67 In this present study, we test the stabilities of the two phases at varying pHs and are able to estimate the boundaries of pH window for the coexistence as shown in Figure 3B. The dashed curve in Figure 3B shows the free energy difference between the two phases ΔF = F center − F wall .…”

Section: Polymer Sequence Design and Gate Architecturementioning

confidence: 95%

Design of Multifunctional Nanogate in Response to Multiple External Stimuli Using Amphiphilic Diblock Copolymer

Huang

Szleifer

2017

J. Am. Chem. Soc.

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Nature uses the interplay between hydrophobic and electrostatic interactions of disordered proteins to orchestrate complicated molecular gates such as the nuclear pore complex to control the transport of biological masses. Inspired by nature, we here theoretically show that well-defined gate shape, sensitive response to pH and salt concentration, and selectivity in cargo transport can be simultaneously achieved by grafting amphiphilic diblock copolymers made of sequence-controlled hydrophobic and ionizable monomers on the inner surface of solid-state nanopore. As a result, multiple functions such as ionic gating and molecular filtering can be implemented into one single copolymer nanogate. The gate structure and thermodynamics is a result of the self-assembly of the sequence-designed copolymer in the confined geometry that minimizes the free energy of the system. Our theory further predicts a phase transition and discontinuous charge regulation of the confined copolymer that allows logical gating in biosensors and nanofluidic devices. As an example of application, a nanolocker with the potential of molecular pumping has also been designed with the cooperation of two amphiphilic copolymer gates. Our results highlight the importance of polymer sequence in nanogating, and these insights can be used to guide the rational design of polymer-coated smart nanopores.

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“…In previous studies of polymer brushes in poor solvent conditions, we have observed the possibility of having bistable systems in equilibrium, where the molecular theory predicted the existence of more than one local free-energy minima with very different morphologies. , In order to test whether bistability is present in the current system, we solved the molecular theory for increasing values of the applied potential until we obtained the conformational transition, and then we decreased the electric field back to the equilibrium condition ( E = 0). The results of this calculation (Figure ) show that for some values of E , two different structures can be obtained, which indicate that this system is bistable.…”

Section: Results and Discussionmentioning

confidence: 99%

Voltage-Triggered Structural Switching of Polyelectrolyte-Modified Nanochannels

2020

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Synthetic solid-state nanochannels modified with polyelectrolyte brushes are an important class of stimuli-responsive nanofluidic devices. This work theoretically addresses the design of a voltage-triggered nanomechanical gate using the collapse transition of a hydrophobic polyelectrolyte brush within a long nanochannel. In poor solvent conditions, a polyelectrolyte brush grafted to the inner surface of a nanochannel can either collapse to its walls or stretch toward its axis in order to form a central dense plug. An applied transmembrane potential favors polyelectrolyte chain conformations that are tilted in the direction of the electric field, and therefore, the transmembrane potential can trigger a transition from the collapsed-to-the-center state to the collapsed-to-the-wall state. This work studied this transition as a function of the length of the polyelectrolyte chains, the hydrophobicity of the polymer backbone, and the pH and ionic strength of the solution. The optimal conditions to achieve a sharp voltage-triggered transition between the collapsed-to-the-wall and the collapsed-to-the-center structures were identified. This work also explored the effect of the voltage-triggered collapse transition on the transport of probe particles of different sizes. It is shown that there is a balance between the permeability of the channel and the selectivity of the two different collapse states for the particle. In the particular system explored in this work, this balance makes the structural transition mostly effective to gate the transport of species with radii in the ∼1 nm range.

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Minimum free-energy paths for the self-organization of polymer brushes

Cited by 7 publications

References 59 publications

Self-assembly of model short triblock amphiphiles in dilute solution

Self-assembly of model short triblock amphiphiles in dilute solution

Design of Multifunctional Nanogate in Response to Multiple External Stimuli Using Amphiphilic Diblock Copolymer

Voltage-Triggered Structural Switching of Polyelectrolyte-Modified Nanochannels

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