Effect of reversible binding on self-assembly and phase separation in coacervate blends Zuzanna Jedlinska and Robert Riggleman University of Pennsylvania In this work, we investigate how reversible bonding modulates self-assembly and phase separation in polymer blends. We perform simulations of coarse-grained models of polymers using the Theoretically Informed Langevin Dynamics (TILD) method. The TILD method is a hybrid particle/field approach where explicit coordinates of the molecules are retained and used to calculate bonded interactions while non-bonded forces (e.g. electrostatics) are calculated by mapping the particles to a density field which leads to a significant speed-up compared to MD implementations. All simulations are performed using our in-house, GPU-accelerated software, MATILDA. FT [1], which is available open-source on GitHub (rar-ensemble/MATILDA.FT). We model polymers as discrete Gaussian chains, with only a fraction of monomers "active" monomers being capable of forming bonds. We study two types of systems - one having only one type of active monomers, and another with two active monomer species. Monomers which belong to different binding types cannot cross-bind, which enables the system to undergo orthogonal phase separation. We investigate the effect of the fraction of active monomers and the energy associated with bond making/breaking on the properties of the coacervates. We quantify the density of the resulting coacervate phases, analyze their connectivity (fraction of bonded monomers and the the number of unique binding partners), and the MSD of the polymer chains allows us to detect the onset of gelation. In addition, in the systems capable of orthogonal phase separation, we quantify the extent to which two phases separate. We study, how these quantities are affected when either excess salt is introduced into the system, or when monomer- monomer repulsion is varied. We anticipate that our results will be useful in the molecular design of orthogonal phase-separating materials, which could be particularly important in controlling the formation of biomolecular condensates. References 1. Jedlinska, Zuzanna M., Christian Tabedzki, Colin Gillespie, Nathaniel Hess, Anita Yang, and Robert A. Riggleman. “MATILDA.FT, a Mesoscale Simulation Package for Inhomogeneous Soft Matter.” arXiv, https://doi.org/10.48550/ arXiv.2302.02474.
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