Predicting the Flory-Huggins χ Parameter for Polymers with Stiffness Mismatch from Molecular Dynamics Simulations

Polymers

Scott T. Milner¹  Daniel J. Kozuch¹  Wenlin Zhang¹ 

[1] Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802, USA;

关键词: polymers;    Flory–Huggins theory;    bead-spring chain;    molecular dynamics;    coarse grain;    chain stiffness;   

DOI  :  10.3390/polym8060241

来源: DOAJ

【 摘 要 】

The Flory–Huggins χ parameter describes the excess free energy of mixing and governs phase behavior for polymer blends and block copolymers. For chemically-distinct nonpolar polymers, the value of χ is dominated by the mismatch in cohesive energy densities of the monomers. For blends of chemically-similar polymers, the entropic portion of χ, arising from non-ideal local packing, becomes more significant. Using polymer field theory, Fredrickson et al. predicted that a difference in backbone stiffness can result in a positive χ for chains consisting of chemically-identical monomers. To quantitatively investigate this phenomenon, we perform molecular dynamic (MD) simulations for bead-spring chains, which differ only in stiffness. From the simulations, we apply a novel thermodynamic integration to extract χ as low as 10- 4per monomer for blends with stiffness mismatch. To compare with experiments, we introduce a standardized effective monomer to map real polymers onto our bead-spring chains. The predicted χ agrees well with experimental values for a wide variety of pairs of chemically-similar polymers.

【 授权许可】

Unknown