Polymer Brush — Steric Repulsion

Brush height H: — Grafting σ: — Confinement: free

Chain length N 20

Grafting density σ 8 chains

Wall separation D free

χ (solvent quality) good

Polymer brushes (Alexander-de Gennes theory): H ∝ N·σ^(1/3) for good solvent. Steric repulsion: f(D) ∝ (H/D)^5/4 − (D/H)^7/4 per unit area. Drag the wall (top slider) toward the brush and watch the repulsion force grow.