Tunable Cylindrical Brushes
Prof. Sergei Egorov (Department of Chemistry, University of Virginia)

We present a self-consistent field theoretical study of the microstructure of concave cylindrical brushes as a function of the cylinder radius, grafting density, grafted chain length, and the solvent quality. We show that the results for the radial monomer density profile and the distribution of the free ends are in good agreement with the corresponding molecular dynamics results.
In addition, we consider conformational behavior of a free macromolecule in a cylindrical brush. The central result is the observed non-monotonous variation of the size of a free chain in a brush-coated tube when the tube radius is systematically changed. An interpretation of this behavior is given by considering the overlap between the free polymer and the grafted chains as a function of the tube radius.
In the second part of the talk, we present a self-consistent field theoretical study of phase separation in binary polymer brushes physisorbed on cylindrical surfaces. In agreement with earlier simulation and experimental work, we find that macrophase separation occurs for two immiscible polymers of the same length, while chain length mismatch between two polymer types promotes microphase separation, with ring-shaped alternating stripes forming perpendicular to the cylinder axis. We observe that the width of the stripes increases with increasing immiscibility, increasing substrate curvature, decreasing mismatch in the chain length, and decreasing amount of adsorbed polymer.
We rationalize these observations by analyzing entropic and energetic contributions to the Helmholtz free energy of the system.