The structure and phase transitions in polymer blends, diblock copolymers and liquid crystalline polymers: The Landau‐Ginzburg approach

Hołyst, Robert; Vilgis, Thomas A.

doi:10.1002/mats.1996.040050401

Cited by 55 publications

(49 citation statements)

References 109 publications

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“…The study of the structure, phase behavior and interfacial properties of polymers has found longstanding and widespread interest. [1][2][3][4][5][6][7][8][9][10] Understanding the phase behavior of mixtures of different kinds of polymers is important scientifically 11 as well as practically. The scientific importance arises from the complex behavior polymer mixtures display, and the practical importance arises from the many industrial applications of these materials.…”

Section: Introductionmentioning

confidence: 99%

Phase separation in mixtures of flexible and semiflexible polymers

Adhikari

Straube

2011

Polym J

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Using off-lattice Monte Carlo simulations, the critical value of the Flory-Huggins parameter, v, for flexible-semiflexible (isotropic-isotropic) polymer systems as a function of the stiffness of the semiflexible components was estimated. The simulation data were compared with those of the mean field, and it was found that both agree very well. The interfacial tension and the width of the flexible-semiflexible polymer systems were also studied for strong and weak segregation limits. Polymer Journal (2011) 43, 751-756; doi:10.1038/pj.2011; published online 20 July 2011Keywords: isotropic-isotropic polymer; phase separation; semiflexible polymers; stiffness disparity INTRODUCTION Different kinds of polymers can be mixed into a single material in different ways, which can lead to a wide range of phase behaviors that directly influence the associated physical properties and applications of polymers. Two different polymers generally do not mix well. The factors that control polymer-polymer phase behavior are the choice of monomers, molecular architecture, composition, molecular size, interaction energies, specific interactions and the 'Equation of state effects' . The study of the structure, phase behavior and interfacial properties of polymers has found longstanding and widespread interest. 1-10 Understanding the phase behavior of mixtures of different kinds of polymers is important scientifically 11 as well as practically. The scientific importance arises from the complex behavior polymer mixtures display, and the practical importance arises from the many industrial applications of these materials. Polymer blends are generally structurally asymmetric, corresponding to species-dependent local intramolecular properties, such as monomer shape, branch content, and persistence length. Such asymmetries are expected to have a major impact on blend thermodynamics and phase diagrams and can give rise to non-Flory-Huggins miscibility behavior. The prediction of the phase behavior of semiflexible polymeric materials is an important step toward the full characterization of the structural and dynamic properties of liquid-crystalline polymeric materials. In polymer blends, it is important to know how the locations of various phases, isotropic and nematic, and their transitions depend on the properties of the two components, their rigidities, polymerization indices, interactions and so on.Differences in chemical structure may also lead to different spatial configurations of the chemical repeat units, corresponding to different persistence lengths, that is, stiffness disparities. 4 Such stiffness disparities may occur even in materials that are chemically very similar, for example, different polyolefins. Liu and Fredrickson 12 have calculated a

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Section: Introductionmentioning

confidence: 99%

Phase separation in mixtures of flexible and semiflexible polymers

Adhikari

Straube

2011

Polym J

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“…A consideration of the thermodynamic behavior of an incompressible melt of binary heteropolymers in the framework of the WSL theory [16][17][18][19][20] …”

Section: Microscopic Wsl Theorymentioning

confidence: 99%

“…, , Γ q q q % [16][17][18][19][20]. The chemical structure of a macromolecule is known to be completely characterized by the set of chemical correlators [21,22].…”

Section: Microscopic Wsl Theorymentioning

confidence: 99%

“…The variables 1 2 , , , l ξ ξ ξ Given the expressions for gfCC-l , one can obtain the vertex functions of expansion (1) by means of the following formulas [16][17][18][19][20] tensors is a sum of several items differing by order with respect to large parameter , which is specified by the number of coinciding points in the l -point correlator. At it is evidently possible to restrict oneself in expressions for…”

Section: Microscopic Wsl Theorymentioning

confidence: 99%

“…The results of the employment of general expressions (19), (20) in the particular cases and are presented in appendices A and B, respectively.…”

Section: Polymer Chains Of Finite Lengthmentioning

confidence: 99%

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Phase Behavior of Weakly-segregated Multiblock Copolymers with Two-scale Periodic Architecture

2006

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Abstract:The phase behavior of a melt of periodic two-scale multiblock copolymers has been theoretically studied in the framework of the Weak-Segregation Limit theory. The effect of the structural symmetry of the macromolecules on the vertex functions of the Landau free energy expansion is considered in detail. The existence of a thermodynamically stable mesophase with a two length-scale space periodicity has been revealed for a melt of monodisperse periodic heteropolymers.

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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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The structure and phase transitions in polymer blends, diblock copolymers and liquid crystalline polymers: The Landau‐Ginzburg approach

Cited by 55 publications

References 109 publications

Phase separation in mixtures of flexible and semiflexible polymers

Phase separation in mixtures of flexible and semiflexible polymers

Phase Behavior of Weakly-segregated Multiblock Copolymers with Two-scale Periodic Architecture

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

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