Conformation of a polymer chain near the solvent critical region. I. The integral equation theory

Vasilevskaya, V. V.; Khalatur, Pavel G.; Khokhlov, Alexei R.

doi:10.1063/1.477125

Cited by 27 publications

(26 citation statements)

References 39 publications

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“…In the critical region of solvent, the conformational behavior of macromolecule is governed by the long-range solvent density fluctuations which induce the indirect ͑solvent-mediated͒ intrachain attraction. It should be noted that this result is in line with the predictions of the self-consistent integral-equation calculations 29 which have been discussed in paper I.…”

Section: ͑2͒supporting

confidence: 90%

“…To study the conformational behavior of flexible-chain polymers immersed in a critical monoatomic solvent, we have used the reference interaction site model ͑RISM͒ formalism and hybrid self-consistent method MC/RISM ͑see preceding paper, 29 hereafter referred to as paper I͒. Some results of this study will be compared to the results of MC simulations described in the present paper.…”

Section: Introductionmentioning

confidence: 99%

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Conformation of a polymer chain near the solvent critical region. II. Monte Carlo simulation

Vasilevskaya

Khalatur

Khokhlov

1998

The Journal of Chemical Physics

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The conformation of hard-sphere polymers in hard-sphere solution calculated by single-chain simulation in a many-body solvent influence functional Using the Monte Carlo ͑MC͒ calculations, we study the conformational behavior of a two-dimensional ͑2D͒ single flexible-chain polymer dissolved in a monoatomic solvent. It is shown that near the solvent critical region the polymer chain can contract. Such a behavior is observed if the radius of fluctuations of solvent density is smaller than the natural size of the N-unit chain with excluded volume interaction ͓RϳN , where Ϸ3/(dϩ2) is the Flory-Edwards exponent͔. On the other hand, the chain goes back to the initial swollen state when the solvent correlation length becomes larger than R. Under these conditions, the polymer chain is effectively confined in a large solvent droplet. We find that the strongly fluctuating solvent can induce significant conformational changes only if there is a rather strong attraction between polymer segments and solvent particles. In this case, the average chain size is a nontrivial function of polymer-solvent attraction: At rather weak affinity of polymer and solvent, the average chain size grows with the increase of this attraction; with further increase of affinity of polymer and solvent, the chain begins to contract. Thus, in the case of high affinity of polymer and solvent, the polymer chain can undergo the complex coil-globule-coil transition. In general, the results of the MC simulations are in reasonable agreement with those obtained from the self-consistent integral-equation calculations.

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Section: ͑2͒supporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Conformation of a polymer chain near the solvent critical region. II. Monte Carlo simulation

Vasilevskaya

Khalatur

Khokhlov

1998

The Journal of Chemical Physics

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“…͑12͒ is consistent with the approach taken in other PRISM studies of polymers in solution that have employed molecular models that only have short-range repulsive site-site interactions. [20][21][22][23] The authors of Refs. 24 and 25 studied a polymer-solvent system with attractive ms and ss interactions and employed a novel closure relation that was a combination of MSA and HNC closures.…”

Section: A Prism Theorymentioning

confidence: 99%

“…[19][20][21] They studied the static properties of repulsive Lennard-Jones chains in a monomeric solvent and found them to be quantitatively consistent with explicit-solvent molecular dynamics ͑MD͒ simulation results for low and moderate solvent densities ͑ ഛ 0.7͒. 19 In addition, they also observed other interesting effects, such as an entropy-driven collapse transition for an athermal polymer/solvent system under certain conditions, 20 as well as collapse of a Lennard-Jones chain in a solvent near the critical point for sufficiently strong monomer-solvent attraction.…”

Section: Introductionmentioning

confidence: 99%

“…19 In addition, they also observed other interesting effects, such as an entropy-driven collapse transition for an athermal polymer/solvent system under certain conditions, 20 as well as collapse of a Lennard-Jones chain in a solvent near the critical point for sufficiently strong monomer-solvent attraction. 21 Mendez et al also applied the hybrid MC/PRISM method to study the properties of polymer solutions for arbitrary polymer density using both simple 22 and atomistic 23 polymer/solvent models. More recently, Livadaru and Kovalenko introduced an alternative approach to study polymer solutions which combines the PRISM formalism with the polymer Green's function method.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical study of solvent effects on the coil-globule transition

Polson

Opps

Risk

2009

The Journal of Chemical Physics

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The coil-globule transition of a polymer in a solvent has been studied using Monte Carlo simulations of a single chain subject to intramolecular interactions as well as a solvent-mediated effective potential. This solvation potential was calculated using several different theoretical approaches for two simple polymer/solvent models, each employing hard-sphere chains and hard-sphere solvent particles as well as attractive square-well potentials between some interaction sites. For each model, collapse is driven by variation in a parameter which changes the energy mismatch between monomers and solvent particles. The solvation potentials were calculated using two fundamentally different methodologies, each designed to predict the conformational behavior of polymers in solution: (1) the polymer reference interaction site model (PRISM) theory and (2) a many-body solvation potential (MBSP) based on scaled particle theory introduced by Grayce [J. Chem. Phys. 106, 5171 (1997)]. For the PRISM calculations, two well-studied solvation monomer-monomer pair potentials were employed, each distinguished by the closure relation used in its derivation: (i) a hypernetted-chain (HNC)-type potential and (ii) a Percus-Yevick (PY)-type potential. The theoretical predictions were each compared to results obtained from explicit-solvent discontinuous molecular dynamics simulations on the same polymer/solvent model systems [J. Chem. Phys. 125, 194904 (2006)]. In each case, the variation in the coil-globule transition properties with solvent density is mostly qualitatively correct, though the quantitative agreement between the theory and prediction is typically poor. The HNC-type potential yields results that are more qualitatively consistent with simulation. The conformational behavior of the polymer upon collapse predicted by the MBSP approach is quantitatively correct for low and moderate solvent densities but is increasingly less accurate for higher densities. At high solvent densities, the PRISM-HNC and MBSP approaches tend to overestimate, while the PRISM-PY approach underestimates the tendency of the solvent to drive polymer collapse.

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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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Conformation of a polymer chain near the solvent critical region. I. The integral equation theory

Cited by 27 publications

References 39 publications

Conformation of a polymer chain near the solvent critical region. II. Monte Carlo simulation

Conformation of a polymer chain near the solvent critical region. II. Monte Carlo simulation

Theoretical study of solvent effects on the coil-globule transition

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

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