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Nanochannels modified with stimuli-responsive copolymer brushes offer a smart nanovalve mechanism. The potential application of these special nanovalves is wide-ranging and includes the areas of drug delivery and signal transduction, as well as molecular machines. In this study, molecular dynamics simulations were performed to study nanovalve systems that use thermo-responsive amphiphilic triblock copolymer brushes grafted onto the surface of the nanochannel. Varying the system temperature facilitated the extension/collapse transition of the copolymer brushes, which resulted in the opening/closing of the nanochannels. The results of the investigation of the effect of the grafting density and the composition of the copolymers on the conformational transition behavior showed that the composition of copolymer has a significant influence on the nanovalve system. A remarkable result is the effectiveness of the use of intermediate or relatively low grafting density in obtaining an ideal controlling effe...

A hybrid particle–continuum method is used to study the shear flow confined between two opposing walls, one of which is coated with polymer chains. Molecular dynamics (MD) is used in the particle region near the brush and Navier–Stokes (NS) equations are applied in the remaining region where the continuum assumption holds. The information exchange from the continuum region to the particle region is implemented using the constrained particle dynamics. Both Couette shear flow and oscillatory flow are considered in the present work. The effect of the shear flow on the conformational characteristics of polymer brushes is analyzed. In the overlap region, the velocities obtained from MD simulations are smoothly connected with those from NS equations. Our investigations demonstrate that the hybrid particle–continuum model is valid in exploring the shear behavior of polymer brushes.

Dissipative particle dynamics (DPD) is used to investigate solvent flow controlled by a cylindrical nanofluidic channel grafted with polymer brushes. Results for monomer and solvent beads density for different solvent quality were obtained, as well as the height and inclination angle of the polymer brushes in Poiseuille flow. The velocity profile and solvent permeability in Poiseuille flow for varying solvent quality were also examined. The polymer brushes expand and inhibit flow under good solvent conditions. However, under poor solvent conditions the chains collapse to open the channel. Additionally, the dependence of the permeability on the grafting density is given. The results indicate that the system is capable of changing the permeability and flow rate drastically upon changing the solvent quality.