Cosolute partitioning in polymer networks: Effects of flexibility and volume transitions

Abstract

We study the partitioning of cosolute particles in a thin film of a semi-flexible polymer network by a combination of coarse-grained (implicit-solvent) stochastic dynamics simulations and mean-field theory. We focus on a wide range of solvent qualities and cosolute-network interactions for selected polymer flexibilities. Our investigated ensemble (isothermal-isobaric) allows the network to undergo a volume transition from extended to collapsed state while the cosolutes can distribute in bulk and network, correspondingly. We find a rich topology of equilibrium states of the network and transitions between them, qualitatively depending on solvent quality, polymer flexibility, and cosolute-network interactions. In particular, we find a novel `cosolute-induced' collapsed state, where strongly attractive cosolutes bridge network monomers albeit the latter interact mutually repulsive. Finally, the cosolutes' global partitioning `landscape', computed as a function of solvent quality and cosolute-network interactions, exhibits very different topologies depending on polymer flexibility. The simulation results are supported by theoretical predictions obtained with a two-component mean-field approximation for the Helmholtz free energy that considers the chain elasticity and the particle interactions in terms of a virial expansion. Our findings have implications on the interpretation of transport processes and permeability in hydrogel films, as realized in filtration or macromolecular carrier systems.

Macromolecules (2017)

References in corpus (3)

• Catalyzed bimolecular reactions in responsive nanoreactors
• Swelling of ionic microgel particles in the presence of excluded-volume interactions: a density functional approach
• Interactions of neutral semipermeable shells in asymmetric electrolyte solutions

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• Cross-linker effect on solute adsorption in swollen thermoresponsive polymer networks
• Phenol release from pNIPAM hydrogels: Scaling Molecular Dynamics simulations with Dynamical Density Functional Theory
• Feedback-controlled solute transport through chemo-responsive polymer membranes