External potential dynamic studies on the formation of interface in polydisperse polymer blends

Qi, Shuanhu; Zhang, Xinghua; Yan, Dadong

doi:10.1063/1.3314730

Cited by 13 publications

(16 citation statements)

References 27 publications

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“…At early times, weak maxima of A-monomer density appear in the A-polymer rich side right next to the interface, which then gradually move away and shrink. A similar phenomenon was reported from DDF studies of interfacial broadening in incompressible polymer blends [14,53]. Apart from this overshooting, the evolution of the interfacial density profiles is similar to that shown in Fig.…”

Section: A Interface Evolution In An A/b Polymer Blendsupporting

confidence: 87%

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Dynamic Density Functional Theories for Inhomogeneous Polymer Systems Compared to Brownian Dynamics Simulations

Schmid

2017

Macromolecules

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Dynamic density functionals (DDFs) are popular tools for studying the dynamical evolution of inhomogeneous polymer systems. Here, we present a systematic evaluation of a set of diffusive DDF theories by comparing their predictions with data from particle-based Brownian dynamics (BD) simulations for two selected problems: Interface broadening in compressible A/B homopolymer blends after a sudden change of the incompatibility parameter, and microphase separation in compressible A:B diblock copolymer melts. Specifically, we examine (i) a local dynamics model, where monomers are taken to move independently from each other, (ii) a nonlocal "chain dynamics" model, where monomers move jointly with correlation matrix given by the local chain correlator, and (iii,iv) two popular approximations to (ii), namely (iii) the Debye dynamics model, where the chain correlator is approximated by its value in a homogeneous system, and (iv) the computationally efficient "external potential dynamics" (EPD) model. With the exception of EPD, the value of the compressibility parameter has little influence on the results. In the interface broadening problem, the chain dynamics model reproduces the BD data best. However, the closely related EPD model produces large spurious artefacts. These artefacts disappear when the blend system becomes incompressible. In the microphase separation problem, the predictions of the nonlocal models (ii-iv) agree with each other and significantly overestimate the ordering time, whereas the local model (i) underestimates it. We attribute this to the multiscale character of the ordering process, which involves both local and global chain rearrangements. To account for this, we propose a mixed local/nonlocal DDF scheme which quantitatively reproduces all BD simulation data considered here.

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Section: A Interface Evolution In An A/b Polymer Blendsupporting

confidence: 87%

“…For comparison, we also study the strictly incompressible limit κN → ∞ as in Ref. [53] (denoted IEPD). As expected, the peak disappears.…”

Section: A Interface Evolution In An A/b Polymer Blendmentioning

confidence: 99%

Dynamic Density Functional Theories for Inhomogeneous Polymer Systems Compared to Brownian Dynamics Simulations

Schmid

2017

Macromolecules

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“…In the present study, the brush polymers were taken to be monodisperse. Real polymer brushes, however, are always polydisperse, and it has been demonstrated that polydispersity significantly alters both the equilibrium properties [52,53] and dynamical properties [54][55][56] of materials. Using a one-dimensional SCF theory, we have performed a preliminary study of a system with an adsorption-active chain embedded in a polydisperse brush with a continuous Schulz-Zimm length distribution.…”

Section: Conclusion and Remarksmentioning

confidence: 99%

Stimuli-Responsive Brushes with Active Minority Components: Monte Carlo Study and Analytical Theory

Klushin

Skvortsov

et al. 2015

Macromolecules

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Using a combination of analytical theory, Monte Carlo simulations, and three dimensional selfconsistent field calculations, we study the equilibrium properties and the switching behavior of adsorption-active polymer chains included in a homopolymer brush. The switching transition is driven by a conformational change of a small fraction of minority chains, which are attracted by the substrate. Depending on the strength of the attractive interaction, the minority chains assume one of two states: An exposed state characterized by a stem-crown-like conformation, and an adsorbed state characterized by a flat two-dimensional structure. Comparing the Monte Carlo simulations, which use an Edwards-type Hamiltonian with density dependent interactions, with the predictions from self-consistent-field theory based on the same Hamiltonian, we find that thermal density fluctuations affect the system in two different ways. First, they renormalize the excluded volume interaction parameter v bare inside the brush. The properties of the brushes can be reproduced by self-consistent field theory if one replaces v bare by an effective parameter veff, where the ratio of second virial coefficients Beff/B bare depends on the range of monomer interactions, but not on the grafting density, the chain length, and v bare . Second, density fluctuations affect the conformations of chains at the brush surface and have a favorable effect on the characteristics of the switching transition: In the interesting regime where the transition is sharp, they reduce the free energy barrier between the two states significantly. The scaling behavior of various quantities is also analyzed and compared with analytical predictions.

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“…31 Recently we generalized the EPD equations to study the polydispersity effect during the structure evolution by introducing the polydispersity dependent Onsager kinetic coefficient. 21 Benefitting from the comprehensive grand potential computed from the SCFT and the molecular structure dependent diffusion coefficient in the diffuse equation, we are certain that the EPD theory can illustrate the evolutionary dynamics in the entire metastable region well. One can find the detail derivation of EPD equations in Refs.…”

Section: B Nucleus Growth Dynamicsmentioning

confidence: 95%

Spinodal assisted growing dynamics of critical nucleus in polymer blends

Zhang

Yan

2012

The Journal of Chemical Physics

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In metastable polymer blends, nonclassical critical nucleus is not a drop of stable phase in core wrapped with a sharp interface, but a diffuse structure depending on the metastability. Thus, forming a critical nucleus does not mean the birth of a new phase. In the present work, the nonclassical growing dynamics of the critical nucleus is addressed in the metastable polymer blends by incorporating self-consistent field theory and external potential dynamics theory, which leads to an intuitionistic description for the scattering experiments. The results suggest that the growth of nonclassical critical nucleus is controlled by the spinodal-decomposition which happens in the region surrounding the nucleus. This leads to forming the shell structures around the nucleus.

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External potential dynamic studies on the formation of interface in polydisperse polymer blends

Cited by 13 publications

References 27 publications

Dynamic Density Functional Theories for Inhomogeneous Polymer Systems Compared to Brownian Dynamics Simulations

Dynamic Density Functional Theories for Inhomogeneous Polymer Systems Compared to Brownian Dynamics Simulations

Stimuli-Responsive Brushes with Active Minority Components: Monte Carlo Study and Analytical Theory

Spinodal assisted growing dynamics of critical nucleus in polymer blends

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