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We investigate the behavior of a single chain condensate formed through polymer-assisted condensation (PAC) [Sommer, J.-U.. Macromolecules2022, 55, 4841–4851]under the influence of an external force using molecular dynamics simulations and mean-field theory. By pulling at the chain ends we observe a first-order phase transition at a critical force, characterized by the coexistence of the condensate and stretched segments of the chain at a fixed deformation. We develop a free energy model capable of accommodating the deformed droplet state and the overstretched chain segments. This enables us to calculate the condensation free energy and the surface tension of the condensate formed by phase separation of the two-component solution induced by the polymer, across various compositions of the solvent mixture. We demonstrate the feasibility of matching a Flory–Huggins-type mean field model to Lennard-Jones fluid simulations. A numerical analysis of this Lennard-Jones equivalent model reveals the scaling behavior of the condensation free energy of the PAC-droplet with respect to the chemical potential of the cosolvent and the interaction energy between the cosolvent and the monomers. We discuss the calculated surface tension for a protein model of the cosolvent. This study is poised to advance our understanding of the physical properties exhibited by biomolecular condensates, particularly those formed on DNA under external tension, by considering DNA-binding proteins as cosolvent particles.

Using molecular dynamics simulations, we study the properties of liquid state polymer–nanoparticle composites confined between two parallel substrates, with an attractive polymer–substrate interaction. Polymers are in the semidilute regime at concentrations far above the overlap point, and nanoparticles are in good solvent and without enthalpic attraction to the substrates. An increase of temperature then triggers the crystallization of nanoparticles on one of the two substrate surfacesa surprising phenomenon, which is explained in terms of scaling theory, such as through competing effects of adsorptionand correlation blobs. Moreover, we show that the first, closely packed layer of nanoparticles on the substrate increases the depletion attraction of additional nanoparticles from the bulk, thereby enhancing and stabilizing the formation of a crystalline phase on the substrate. Within the time frame accessible to our numerical simulations, the crystallization of nanoparticles was irreversible; that is, their crystalline phase, once created, remained undamaged after a decrease of the temperature. Our study leads to a class of thermoreactive nanomaterials, in which the transition between a homogeneous state with dissolved nanoparticles and a surface-crystallized state is triggered by a temperature jump.