Fluctuation Effects in Semiflexible Diblock Copolymers

Mao, Shifan; MacPherson, Quinn; Spakowitz, Andrew J.

doi:10.1021/acsmacrolett.7b00638

Cited by 6 publications

(15 citation statements)

References 45 publications

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“…For example, we performed simulations for mono-6-2 and mono-9-3 at T sim = 493 K. Both are found to form homogeneous disordered phases, which leads to the conclusion that χ MF ( y = 4) > χ MF ( y = 3) (Table S5). Second, the effects of short chain length and semiflexibility are not taken into account in the fitting of mono- and di-oligomers data using the mean-field AB diblock copolymer model and the mean-field AB 2 star polymer model, respectively. , A recent computational work by Mao et al . has discussed the effects of finite chain length and semiflexibility on the order–disorder transition point χ N ODT for symmetric diblock polymers.…”

Section: Resultsmentioning

confidence: 99%

“…Second, the effects of short chain length and semiflexibility are not taken into account in the fitting of monoand di-oligomers data using the mean-field AB diblock copolymer model and the mean-field AB 2 star polymer model, respectively. 84,85 A recent computational work by Mao et al 85 has discussed the effects of finite chain length and semiflexibility on the order−disorder transition point χN ODT for symmetric diblock polymers. According to their results, 85 χN ODT differs by around 20% from the mean-field theory for symmetric diblock copolymers that have similar chain length and semiflexibility as HCBOs.…”

Section: Resultsmentioning

confidence: 99%

“…84,85 A recent computational work by Mao et al 85 has discussed the effects of finite chain length and semiflexibility on the order−disorder transition point χN ODT for symmetric diblock polymers. According to their results, 85 χN ODT differs by around 20% from the mean-field theory for symmetric diblock copolymers that have similar chain length and semiflexibility as HCBOs. Despite that the quantitative determination of χ is hampered by the lack of χN ODT (f) theory data for oligomeric semiflexible chains, our simulation data demonstrate that the χ MF values from the semiquantitative fitting in our manuscript are only for comparison purposes and not accurate reflections of only the interactions between the two blocks in standard block polymer models.…”

Section: Resultsmentioning

confidence: 99%

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Computational Design of High-χ Block Oligomers for Accessing 1 nm Domains

et al. 2018

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Molecular dynamics simulations are used to design a series of high-χ block oligomers (HCBOs) that can self-assemble into a variety of mesophases with domain sizes as small as 1 nm. The exploration of these oligomers with various chain lengths, volume fractions, and chain architectures at multiple temperatures reveals the presence of ordered lamellae, perforated lamellae, and hexagonally packed cylinders. The achieved periods are as small as 3.0 and 2.1 nm for lamellae and cylinders, respectively, which correspond to polar domains of approximately 1 nm. Interestingly, the detailed phase behavior of these oligomers is distinct from that of either solvent-free surfactants or block polymers. The simulations reveal that the behavior of these HCBOs is a product of an interplay between both "surfactant factors" (headgroup interactions, chain flexibility, and interfacial curvature) and "block polymer factors" (χ, chain length N, and volume fraction f). This insight promotes the understanding of molecular features pivotal for mesophase formation at the sub-5 nm length scale, which facilitates the design of HCBOs tailored toward particular desired morphologies.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Computational Design of High-χ Block Oligomers for Accessing 1 nm Domains

et al. 2018

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“…To find the effect of chain semiflexibility on the phase behavior of diblock copolymers, past studies use SCFT of wormlike chains [5,[15][16][17][18], neglecting concentration fluctuations. Simulations of semiflexible copolymers [19][20][21] provide insight into the role of polymer rigidity in the morphology and the ODT. In this work, we aim to account for the finite molecular weight effects of diblock copolymers by considering the effects of chain semiflexibility and concentration fluctuations.…”

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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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“…We quantify the extent of phase separation in the simulations via the magnitude of compositional fluctuations in a manner analogous to other simulation models of polymer phase separation . We first define a global number density of the i = A and B components, , where the quantity is the overall number of particles in the box volume V .…”

Section: Model and Methodsmentioning

confidence: 99%

Implicit Side-Chain Model and Experimental Characterization of Bottlebrush Block Copolymer Solution Assembly

et al. 2021

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Bottlebrush polymers are a class of macromolecules with linear backbones and densely grafted side chains, possessing unique physical properties due to strong steric interactions between the side chains. These interactions serve to both stiffen the molecular contour and impart a molecular width, leading to material properties distinct from linear counterparts. This is especially important for the case of diblock bottlebrush copolymers, where side-chain-induced stiffness leads to assembly on large length scales while simultaneously suppressing molecular entanglements that would otherwise hinder self-assembly. The resulting microphase-separated structure is thus ideal for photonic crystals, due to the formation of long-range order with features on length scales commensurate with the wavelength of visible light. Despite the usefulness of block copolymer bottlebrush materials, it remains challenging to model their self-assembly in solution due to the additional side-chain degrees of freedom, which are computationally expensive to resolve. In this paper, we develop a simulation model for bottlebrush block copolymer solution selfassembly that adapts a recently developed implicit side-chain model, accounting for the effect of side chains within a simplified, beadrod polymer model. We further extend this model by deriving an intermolecular interaction potential from scaling arguments and show that we can predict bottlebrush self-assembly over a range of block fractions and polymer concentrations. For all architectures studied, we observe an order−disorder transition to lamellar morphologies and regions of significant compositional fluctuations in the disordered phase. We compare computational predictions of self-assembly to experiments, using diblock bottlebrush copolymers synthesized with poly(norbornene) backbones and polystyrene side chains and poly(lactic acid) side chains on each block. We show that the simulation structure factors match well with experimental scattering and indicate the emergence of self-assembly at high concentrations.

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Fluctuation Effects in Semiflexible Diblock Copolymers

Cited by 6 publications

References 45 publications

Computational Design of High-χ Block Oligomers for Accessing 1 nm Domains

Computational Design of High-χ Block Oligomers for Accessing 1 nm Domains

Polymer Semiflexibility Induces Nonuniversal Phase Transitions in Diblock Copolymers

Implicit Side-Chain Model and Experimental Characterization of Bottlebrush Block Copolymer Solution Assembly

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