Polymer-grafted nanopores are used in several nanotechnological applications which demand control of structural and hydration properties of the grafted polymers. By means of atomistic molecular dynamics simulations, we systematically investigate the chain length and grafting density effects on the conformation and hydration of poly(ethylene oxide) (PEO) grafted to gold nanopores of different radii. We find that if the pore size exceeds the polymer length, increasing the grafting density or chain length for a given pore results in conformational changes of the polymer from pancake-like shapes to well-hydrated overlapping mushrooms to a denser less hydrated polymer brush. We demonstrate that an increase of pore curvature results in considerable polymer crowding within the pore, which translates into an increase of the effective grafting density, σ eff , which has to be taken into consideration when concave nanopores and planar and convex surfaces are compared. We show that for a given polymer grafting density and chain length, a decrease in the pore radius R results in an increased radial orientation, and for a low grafting density, there is a slight increase of the grafted layer height H until the polymer chains fill the pore (R ∼ H) and start folding near the pore surface, conforming into a cone-shape with a further brush height decrease until the high-density limit is reached. The properties of polymer-grafted nanopores, such as water exchange and gating capability, depend on the polymer conformation and hydration, which are strongly influenced by the polymer grafting density and differ for polymer-filled and open nanopores.

Bottlebrush polymers (BBPs) of different architecture are of considerable interest for a broad range of applications, including nanomedicine, electronics, and self-healing materials. Using atomistic molecular dynamics simulations, we investigate and compare the structural and hydration properties of cyclic and linear poly(vinyl alcohol)-graft-poly(ethylene oxide) (PVA-g-PEO N sc ) BBPs in aqueous solution as functions of PEO side-chain length, N sc. We find that overall cyclic BBPs are smaller than the corresponding linear BBPs and their shape changes from donutlike to disklike to starlike with increasing side-chain length, while linear BBPs vary in shape from an expanded coil to a rod/cylinder. The radius of gyration of cyclic BBPs increases with an increase of the side-chain length at a somewhat slower rate than the linear BBPs but follows the same scaling R g ∼ N sc 0.58 in the limit of long side chains. For short grafts, we determine that the persistence length, l p, for both cyclic and linear BBPs increases in a similar manner following an l p ∼ N sc 0.54 dependence. In the long side-chain limit, the persistence length (l p) of cyclic BBP saturates, while for linear BBPs l p strongly increases following the expected scaling relation l p ∼ N sc 15/8. We propose a scaling model that shows that the fraction of side-chains located inside the cyclic BBPs depends on the radius of the backbone ring and significantly decreases with an increase of graft length. For both cyclic and linear BBPs, the hydrogen bonding between PEO side chains and water is somewhat reduced near the backbone, where local chain stretching is observed, while reaching full hydration on the periphery. Overall, the hydration shell within 1 nm of the cyclic BBP backbone is found to be more dynamically stable compared to linear BBPs.