Phase equilibrium in mixtures of flexible and stiff polymers studied by Monte Carlo simulation

Abstract

We present computer simulations of dense polymer mixtures composed of flexible and semiflexible chains. It is found that a demixing transition takes place below a certain degree of flexibility, even without introducing repelling interactions between the two polymers except the excluded volume condition. Computing the equilibrium concentration of phases for various temperatures, a phase diagram for the binary mixture is found. The results show qualitative agreement with the Flory lattice theory of stiff chains.

Phase Separation and Nematic Order in Lyotropic Solutions: Two Types of Polymers with Different Stiffnesses in a Common Solvent

“…Phase equilibria in solutions of chains in the limit where the contour lengths of both types of chains are much larger than their persistence lengths have already been studied by Semenov and Subbotin, by extending the Khokhlov–Semenov–Odijk approach. − Since this region of extremely long polymer chains is out of consideration here, we do not discuss the details of that work. Phase equilibria in binary mixtures of completely rigid and flexible molecules have been actively studied theoretically, both via various mean-field approaches ,,,,− and by computer simulations. ,, Escobedo and de Pablo studied a binary mixture of semiflexible and fully rigid 16-mers via MC simulations in the expanded Gibbs ensemble at constant pressure P = 0.14 k B T /σ 3 , which corresponds to the pressure reduced with respect to the I–N coexistence pressure of the rigid component equal to P / P B coex = 1.3. They have constructed the corresponding isobaric phase diagram in the plane of the inverse stiffness parameter of the semiflexible component A, κ A –1 , vs the mole fraction of the rigid component B, X B .…”

“…Phase equilibria in binary mixtures of completely rigid and flexible molecules have been actively studied theoretically, both via various mean-field approaches 15,16,30,31,52−55 and by computer simulations. 33,56,57 Escobedo and de Pablo 33 studied a binary mixture of semiflexible and fully rigid 16-mers via MC simulations in the expanded Gibbs ensemble at constant pressure P = 0.14k B T/σ 3 , which corresponds to the pressure reduced with respect to the I−N coexistence pressure of the rigid component equal to P/P B coex = 1.3. They have constructed the corresponding isobaric phase diagram in the plane of the inverse stiffness parameter of the semiflexible component A, κ A −1 , vs the mole fraction of the rigid component B, X B .…”

Expansion of Intrinsically Disordered Proteins Increases the Range of Stability of Liquid–Liquid Phase Separation

“…That rigidification of extended IDR states that increases the stability of their condensates may also help explain what drives the liquid-gel transitions which are implicated in the formation of pathological aggregates [ 3 , 16 , 17 , 18 ]. Moreover, subtle effects in polymer stiffness and conformation has also been shown to drive demixing of polymer mixtures into two-phase equilibrium [ 109 ].…”

Interfacial Properties of Flexible and Semiflexible Polymers

“…The stiffness disparity is a truly polymeric feature, as the length scale is between the local, monomeric size and the radius of gyration. Gauger and Pakula [3] have investigated a mixture of flexible and very stiff chains in the canonical ensemble and used the sub-block method to analyze their simulation data. Due to the stiffness and the excluded volume constraints, they found evidences for a separation into a pure phase of stiff chains and a phase of mixed composition.…”