A theory for compressible binary lattice polymers: Influence of chain conformational properties

Wang, Suxin; Nies, Erik; Cifra, Peter

doi:10.1063/1.477182

Cited by 5 publications

(7 citation statements)

References 32 publications

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“…These values were obtained by assuming value of γ l = 0.22 (i.e., a lattice coordination number of 9), and calculating γ s by a fit to critical point data, Values of γ s between 0.25 and 0.30 were obtained, consistent with simulations, given the difference in lattice coordination number . Furthermore, it was pointed out to us by one of the reviewers of this paper that Wang et al also accounted for intramolecular contacts in polymer blends and derived equations that are essentially identical to ours (their derivation is far more rigorous, we might add). These authors also calculated the fraction of intramolecular contacts for chains of different lengths, obtaining results that are consistent with those we obtained.…”

Section: Conformational Contributions To Self-concentrationsupporting

confidence: 66%

Self-Contacts, Self-Concentration, and the Composition Dependence of the Glass Transition Temperature in Polymer Mixtures

Painter¹,

Coleman²

2009

Macromolecules

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Self-concentration, a consequence of chain connectivity, is an important factor in determining the properties of polymer mixtures. It is proposed that self-concentration has two components. First, there is a "covalent connectivity effect", which manifests itself in the probability that a site adjacent to a chosen segment on a chain is occupied by a like or unlike segment; second, there is a "conformational connectivity effect" that is a consequence of a chain bending back on itself through both local and long-range factors that depend on the flexibility of the chain. This latter component is modeled using a contact point approach developed in previous work. If the covalent connectivity effect is treated using a lattice model, there is a cancelation of terms and noncovalent contacts do not contribute to self-concentration in calculating the average properties of polymer blends. Nevertheless, when covalent contacts are included together with conformational self-contacts in order to calculate the composition dependence of the glass transition temperature, an equation corresponding to the self-consistent form of the Lodge-McLeish model derived by Lipson and Milner is recovered. In the systems studied so far, this approach leads to consistent results, with values of self-concentration terms that correspond to what would be expected in terms of connectivity and self-contact parameters determined in previous work. This parameter appears to be a transferable constant that depends on the microstructure, conformation and to some degree the molecular weight of the polymer.

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Section: Conformational Contributions To Self-concentrationsupporting

confidence: 66%

Self-Contacts, Self-Concentration, and the Composition Dependence of the Glass Transition Temperature in Polymer Mixtures

Painter¹,

Coleman²

2009

Macromolecules

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“…Freed and coworkers reported that the quasi-chemical theory of Guggenheim gives very good agreement with the simulation data [ 51 , 58 ]. For not too large interaction energies, the Guggenheim theory reduces to the Huggins approximation; hence, the Huggins theory is in this case also in very good agreement with these simulation data [ 51 , 58 , 69 , 70 ].…”

Section: Discussionsupporting

confidence: 54%

Effect of End Groups on the Cloud Point Temperature of Aqueous Solutions of Thermoresponsive Polymers: An Inside View by Flory–Huggins Theory

Dang,

Nies

2024

Polymers

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In an effort to gain insight into the origin of the effects of end groups on the cloud point temperature (Tcp) as a function of the polymer molar mass of thermoresponsive polymers with lower critical solution behavior in dilute aqueous solutions, we use the Flory–Huggins (FH) theory amended for end groups. The theory was applied to available experimental data sets of poly(N-isopropylacrylamide) (PNIPAM), poly(4-vinylbenzyl methoxytris(oxyethylene) ether) (PTEGSt), and poly(α-hydro-ω-(4-vinylbenzyl)tetrakis(oxyethylene) ether) (PHTrEGSt). The theory relates the variations in TcpM,ϕcp for different end groups to the effective FH χ parameter of the end groups and explains the qualitative notion that the influence of the end groups is related to the hydrophobicity/hydrophilicity of the end groups relative to that of the so called intrinsic TcpM,ϕcp response of a polymer without end groups. The limits to the applicability of the FH theory are established, and a set of possible theoretical improvements is considered. The ultimate scrutiny of the simple FH theory and suggested improved theories must await the measurement of truly thermodynamic cloud points; the available cloud points are merely estimations of the thermodynamic cloud point, for which the deviation to the true cloud point cannot be established with sufficient accuracy.

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“…The density dependence of the chain conformations on the density has been investigated by Weinhold et al 92) and Wang et al 93) They derived the density dependence of the chain conformations due to the correlation between the intermolecular contacts and the extension of the chains. The comparison of their approach with Monte Carlo simulations exhibited reasonable agreement for short and intermediate chain lengths.…”

Section: X3mentioning

confidence: 99%

“…If the pure components exhibit a strong dependence of the density upon pressure and temperatures, this will also affect the conformations of the molecules and give rise to a composition dependence in a blend. The density dependence of the chain conformations on the density has been investigated by Weinhold et al 93 and Wang et al 94 . They derived the density dependence of the chain conformations due to the correlation between the intermolecular contacts and the extension of the chains.…”

Section: Single Chain Conformationsmentioning

confidence: 99%

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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A theory for compressible binary lattice polymers: Influence of chain conformational properties

Cited by 5 publications

References 32 publications

Self-Contacts, Self-Concentration, and the Composition Dependence of the Glass Transition Temperature in Polymer Mixtures

Self-Contacts, Self-Concentration, and the Composition Dependence of the Glass Transition Temperature in Polymer Mixtures

Effect of End Groups on the Cloud Point Temperature of Aqueous Solutions of Thermoresponsive Polymers: An Inside View by Flory–Huggins Theory

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

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