Universality between Experiment and Simulation of a Diblock Copolymer Melt

Beardsley, Tom; Matsen, Mark W.

doi:10.1103/physrevlett.117.217801

Cited by 31 publications

(31 citation statements)

References 31 publications

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“…The ODT is the point where the lamellar and disordered phases coexist and in our lattice models it is signified by an abrupt change in the average number of A-B contacts n AB [32,35,37,38]. Therefore, by running a series of parallel tempering replicas that span the lamellar and disordered phases, we can collect statistics for n AB and detect the transition.…”

Section: Monodisperse Order-disorder Transitionmentioning

confidence: 99%

Simple and Accurate Calibration of the Flory–Huggins Interaction Parameter

2020

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This paper improves upon a standard method of determining the Flory–Huggins χ parameter, whereby experimental order–disorder transitions (ODTs) of symmetric diblock polymer melts are fit to the mean-field prediction, (χN)ODT = 10.495. The improvement is achieved by switching to an accurate prediction of (χN)ODT from Glaser et al. (Phys. Rev. Lett. 2014, 113, 068302), supplemented with corrections for the small degrees of polydispersity and compositional asymmetry that inevitably exist in real diblock polymers. The first correction is evaluated by simulating polydisperse diblocks over a wide range of invariant polymerization indices, and the second correction is extracted from analogous simulations for compositionally asymmetric diblocks by Ghasimakbari and Morse (Macromolecules 2020, 53, 7399). The resulting calibration method is then demonstrated on 19 different chemical pairs, using previously published experimental data. It provides a considerable increase in accuracy, but yet is nearly as simple to apply as the original version.

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Section: Monodisperse Order-disorder Transitionmentioning

confidence: 99%

Simple and Accurate Calibration of the Flory–Huggins Interaction Parameter

2020

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“…Consequently, they can all be mapped onto the standard Gaussian chain model (GCM) [ 5 ], which is a minimal model that treats block copolymer systems as incompressible melts of thin elastic threads that interact by pairwise contact forces. At present, the most accurate method of performing the mapping is the Morse calibration [ 4 , 6 ], which has been well demonstrated for experiments [ 7 ] and particle-based simulations [ 8 , 9 , 10 , 11 , 12 ], as well as field-theoretic simulations [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

Field-Theoretic Simulations for Block Copolymer Melts Using the Partial Saddle-Point Approximation

Matsen

Beardsley

2021

Polymers

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Field-theoretic simulations (FTS) provide an efficient technique for investigating fluctuation effects in block copolymer melts with numerous advantages over traditional particle-based simulations. For systems involving two components (i.e., A and B), the field-based Hamiltonian, Hf[W−,W+], depends on a composition field, W−(r), that controls the segregation of the unlike components and a pressure field, W+(r), that enforces incompressibility. This review introduces researchers to a promising variant of FTS, in which W−(r) fluctuates while W+(r) tracks its mean-field value. The method is described in detail for melts of AB diblock copolymer, covering its theoretical foundation through to its numerical implementation. We then illustrate its application for neat AB diblock copolymer melts, as well as ternary blends of AB diblock copolymer with its A- and B-type parent homopolymers. The review concludes by discussing the future outlook. To help researchers adopt the method, open-source code is provided that can be run on either central processing units (CPUs) or graphics processing units (GPUs).

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“…Such observations are recently argued to be caused by chain polydispersity (i.e. a distribution of molecular weight) [13]. However, the dependence of the ODT on average molecular weight is not explored in this work, and the chain lengths that were simulated in Ref.…”

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confidence: 97%

“…However, the dependence of the ODT on average molecular weight is not explored in this work, and the chain lengths that were simulated in Ref. [13] are as short as N = 40. In this work, we demonstrate that at such lengths polymer semiflexibility also plays a significant role in the behavior.…”

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confidence: 99%

Polymer Semiflexibility Induces Nonuniversal Phase Transitions in Diblock Copolymers

2018

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The order-disorder phase transition and the associated phase diagrams of semiflexible diblock copolymers are investigated using the wormlike chain model, incorporating concentration fluctuations. The free energy up to quartic order in concentration fluctuations is developed with chain-rigidity-dependent coefficients, evaluated using our exact results for the wormlike chain model, and a one-loop renormalization treatment is used to account for fluctuation effects. The chain length N and the monomer aspect ratio α directly control the strength of immiscibility (defined by the Flory-Huggins parameter χ) at the order-disorder transition and the resulting microstructures at different chemical compositions f_{A}. When monomers are infinitely thin (i.e., large aspect ratio α), the finite chain length N lowers the χN at the phase transition. However, fluctuation effects become important when chains have a finite radius, and a decrease in the chain length N elevates the χN at the phase transition. Phase diagrams of diblock copolymers over a wide range of N and α are calculated based on our fluctuation theory. We find that both finite N and α enhance the stability of the lamellar phase above the order-disorder transition. Our results demonstrate that polymer semiflexibility plays a dramatic role in the phase behavior, even for large chain lengths (e.g., N≈100).

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Universality between Experiment and Simulation of a Diblock Copolymer Melt

Cited by 31 publications

References 31 publications

Simple and Accurate Calibration of the Flory–Huggins Interaction Parameter

Simple and Accurate Calibration of the Flory–Huggins Interaction Parameter

Field-Theoretic Simulations for Block Copolymer Melts Using the Partial Saddle-Point Approximation

Polymer Semiflexibility Induces Nonuniversal Phase Transitions in Diblock Copolymers

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