Scaling Exponent and Effective Interactions in Linear and Cyclic Polymer Solutions: Theory, Simulations, and Experiments

TE Gartner and FM Haque and AM Gomi and SM Grayson and MJA Hore and A Jayaraman, MACROMOLECULES, 52, 4579-4589 (2019).

DOI: 10.1021/acs.macromol.9b00600

Cyclic polymers have garnered increasing attention in the materials community as lack of free-chain ends in cyclic polymers results in significant differences in structure, thermodynamics, and dynamics compared to their linear counterparts. Yet, key open questions remain about how cyclic polymer chain conformations and effective interactions in solution change as a function of solvent quality, ring closure chemistry, and the presence/absence of common synthetic impurities. We use coarse-grained molecular dynamics simulations, polymer reference interaction site model theory, and small-angle neutron-scattering experiments on polystyrene in d-cyclohexane to demonstrate how linear and cyclic polymer chain configurations, scaling, and effective interactions are influenced by solvent quality and polymer concentration. We find that the balance between the available intraversus interchain contacts in solution dictate the trends in cyclic polymer size scaling and effective polymer-solvent and polymer-polymer interactions; these results are largely insensitive to the ring closure chemistry and the presence of linear or cyclic dimer impurities. This study provides the broader polymer science and engineering community fundamental insights into how synthesis, purification, and assembly of cyclic polymers in solvent(s) impact the resulting chain structure and polymer solution thermodynamics.

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