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Macromolecular ‘size’ and ‘hardness’ drives structure in solvent-swollen blends of linear, cyclic, and star polymers

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Abstract

In this paper, we apply molecular simulation and liquid state theory to uncover the structure and thermodynamics of homopolymer blends of the same chemistry and varying chain architecture in the presence of explicit solvent species. We use hybrid Monte Carlo (MC)/molecular dynamics (MD) simulations in the Gibbs ensemble to study the swelling of ∼12 000 g mol−1 linear, cyclic, and 4-arm star polystyrene chains in toluene. Our simulations show that the macroscopic swelling response is indistinguishable between the various architectures and matches published experimental data for the solvent annealing of linear polystyrene by toluene vapor. We then use standard MD simulations in the NPT ensemble along with polymer reference interaction site model (PRISM) theory to calculate effective polymer–solvent and polymer–polymer Flory–Huggins interaction parameters (χeff) in these systems. As seen in the macroscopic swelling results, there are no significant differences in the polymer–solvent and polymer–polymer χeff between the various architectures. Despite similar macroscopic swelling and effective interaction parameters between various architectures, the pair correlation function between chain centers-of-mass indicates stronger correlations between cyclic or star chains in the linear–cyclic blends and linear–star blends, compared to linear chain–linear chain correlations. Furthermore, we note striking similarities in the chain-level correlations and the radius of gyration of cyclic and 4-arm star architectures of identical molecular weight. Our results indicate that the cyclic and star chains are ‘smaller’ and ‘harder’ than their linear counterparts, and through comparison with MD simulations of blends of soft spheres with varying hardness and size we suggest that these macromolecular characteristics are the source of the stronger cyclic–cyclic and star–star correlations.

Graphical abstract: Macromolecular ‘size’ and ‘hardness’ drives structure in solvent-swollen blends of linear, cyclic, and star polymers

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Publication details

The article was received on 08 Nov 2017, accepted on 12 Dec 2017 and first published on 18 Dec 2017


Article type: Paper
DOI: 10.1039/C7SM02199B
Citation: Soft Matter, 2018, Advance Article
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    Macromolecular ‘size’ and ‘hardness’ drives structure in solvent-swollen blends of linear, cyclic, and star polymers

    T. E. Gartner and A. Jayaraman, Soft Matter, 2018, Advance Article , DOI: 10.1039/C7SM02199B

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