Single-Chain Conformations in Symmetric Binary Polymer Blends:  Quantitative Comparison between Self-Consistent Field Calculations and Monte Carlo Simulations

Müller, Marcus

doi:10.1021/ma9807973

Cited by 33 publications

(48 citation statements)

References 70 publications

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“…Upon decreasing the temperature close to the critical temperature, the chains shrink by about 3%. The asymptotic expression overestimates the 26) effect slightly, while the full SCF calculations yield an improved estimate. The composition dependence of the chain conformations in the one phase region is investigated in Fig.…”

Section: X3mentioning

confidence: 88%

“…Monte Carlo simulations suggest 47) that one possible mechanism of conformational changes in blends is associated to exchanging energetically unfavorable intermolecular contacts for attractive intramolecular contacts upon reducing the molecule's spatial extension. Attributing this shrinking of the minority component to a balance between the entropy loss due to deviations from the unperturbed conformations and the energy gain upon shrinking, we can estimate the magnitude of conformational changes 26) : Flexible chains are describable by the Gaussian chain model. Within this framework a deviation from the unperturbed chain extension R 0 gives rise to an entropic force of the form…”

Section: X12mentioning

confidence: 99%

“…However, the overestimation of the critical temperature is smaller than for chain length N = 16. The dashed line shows a mean field estimate 26) , which includes composition fluctuations on the length scale of a small cluster which consists of n c = 14 polymers, but treats long range composition fluctuations in a mean field fashion. Of course, this theory also yields a parabolic shape of the binodals, but results in an improved estimate of the critical temperature.…”

Section: Symmetric Blendsmentioning

confidence: 99%

“…From ref. 26) mainly determined by packing and approximately decouples from the chain conformations. For long chains, the conformational changes merely result in an exchange of inter-and intramolecular contacts.…”

Section: Single Chain Conformationsmentioning

confidence: 99%

“…A more detailed self-consistent field (SCF) theory for single chain conformations in dense blends has been developed in ref. 26) In the framework of the SCF calculations the statistical mechanics of a cluster of n c neighboring polymers is solved. Interactions inside the cluster are treated exactly, whereas interactions between the n c members of the cluster and polymers outside the cluster are treated in a mean field approximation.…”

Section: X3mentioning

confidence: 99%

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Miscibility behavior and single chain properties in polymer blends: a bond fluctuation model study

Müller¹

1999

Macromol. Theory Simul.

106

113

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SUMMARY: Computer simulation studies on the miscibility behavior and single chain properties in binary polymer blends are reviewed. We consider blends of various architectures in order to identify important architectural parameters on a coarse grained level and study their qualitative consequences for the miscibility behavior. The phase diagram, the relation between the exchange chemical potential and the composition, and the intermolecular pair correlation functions for symmetric blends of linear chains, blends of cyclic polymers, blends with an asymmetry in cohesive energies, blends with different chain lengths, blends with distinct monomer shapes, and blends with a stiffness disparity between the components are discussed. For strictly symmetric blends the Flory-Huggins theory becomes quantitatively correct in the long chain length limit, when the v parameter is identified via the intermolecular pair correlation function. For small chain lengths composition fluctuations are important. They manifest themselves in 3D Ising behavior at the critical point and an upward parabolic curvature of the v parameter from small-angle neutron scattering close to the critical point. The ratio between the mean field estimate and the true critical temperature decreases like v p aqb 3 for long chain lengths. The chain conformations in the minority phase of a symmetric blend shrink as to reduce the number of energeticaly unfavorable interactions. Scaling arguments, detailed self-consistent field calculations and Monte Carlo simulations of chains with up to 512 effective segments agree that the conformational changes decrease around the critical point like 1a N p . Other mechanisms for a composition dependence of the single chain conformations in asymmetric blends are discussed. If the constituents of the blends have non-additive monomer shapes, one has a large positive chain-length-independent entropic contribution to the v parameter. In this case the blend phase separates upon heating at a lower critical solution temperature. Upon increasing the chain length the critical temperature approaches a finite value from above. For blends with a stiffness disparity an entropic contribution of the v parameter of the order 10 -3 is measured with high accuracy. Also the enthalpic contribution increases, because a back folding of the stiffer component is suppressed and the stiffer chains possess more intermolecular contacts. Two aspects of the single chain dynamics in blends are discussed: (a) The dynamics of short non-entangled chains in a binary blend are studied via dynamic Monte Carlo simulations. There is hardly any coupling between the chain dynamics and the thermodynamic state of the mixture. Above the critical temperatures both the translational diffusion and the relaxation of the chain conformations are independent of the temperature. (b) Irreversible reactions of a small fraction of reactive polymers at a strongly segregated interface in a symmetric binary polymer blend are investigated. End-functionalized homopolymers of different...

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Section: X3mentioning

confidence: 88%

Section: X12mentioning

confidence: 99%

Section: Symmetric Blendsmentioning

confidence: 99%

Section: Single Chain Conformationsmentioning

confidence: 99%

Section: X3mentioning

confidence: 99%

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Miscibility behavior and single chain properties in polymer blends: a bond fluctuation model study

Müller¹

1999

Macromol. Theory Simul.

106

113

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Phase Transformation

Binder

Müller

2003

Encyclopedia of Polymer Science and Technology

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This article briefly summarizes some key theoretical concepts about phase transformations, discusses the extent to which they differ from related phenomena in other materials, and mentions a few typical experiments to introduce the main techniques used to study such phase transitions. Phase transformations of polymeric materials, such as unmixing of a polymer solution or polymer blend, or the crystallization of a polymer melt or its glass transition into an amorphous structure, are very common phenomena and have important applications. Polymers in the solid state rarely reach full thermal equilibrium. Of course, all amorphous materials can be considered as frozen fluids, whereas polymers typically are semicrystalline, where amorphous regions alternate with crystalline lamellae, and the detailed structure and properties are history‐dependent. Such out‐of‐equilibrium aspects are out of the scope of the present article, which rather emphasizes general facts of the statistical thermodynamics of phase transitions and their applications to polymers in fluid phases.

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Phase Transformation

Binder¹,

Müller²

2016

Encyclopedia of Polymer Science and Technology

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This article briefly summarizes some key theoretical concepts about phase transformations, discusses the extent, to which they differ from related phenomena in other materials, and mentions a few typical experiments to introduce the main techniques used to study such phase transitions. Phase transformations of polymeric materials, such as unmixing of polymer solutions or polymer blends, or the self‐assembly of copolymer materials into spatially modulated structures are very common phenomena and have important applications. This article focuses on the bulk thermodynamics, phase behavior and critical phenomena, interface and surface properties, and basic principles of structure formation (spinodal demixing and nucleation) in fluid polymer systems. Polymers in the solid state, that is, glassy or semicrystalline systems, rarely reach full thermal equilibrium and properties are history dependent. Such out‐of‐equilibrium aspects are beyond the scope of the present article, which rather emphasizes general aspects of the statistical thermodynamics of phase transitions and their applications to polymers in fluid phases.

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Single-Chain Conformations in Symmetric Binary Polymer Blends: Quantitative Comparison between Self-Consistent Field Calculations and Monte Carlo Simulations

Cited by 33 publications

References 70 publications

Miscibility behavior and single chain properties in polymer blends: a bond fluctuation model study

Miscibility behavior and single chain properties in polymer blends: a bond fluctuation model study

Phase Transformation

Phase Transformation

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