Slip behavior in polymethylmethacrylate films in dependence of self-assembled monolayer wettability

The slip behavior of polymethylmethacrylate (PMMA) films prepared on self-assembled monolayers (SAM) supported by Si substrate was investigated according to the wettability of the SAM. To this end, the dewetting of thermally annealed PMMA films was measured varying the surface energies of underlyed SAM. Total surface energy (γt) of SAM increased with increasing UV exposure time. At surface energy of <31.3 mJ/m2, the PMMA films showed slip behavior; radius of holes (R) ∝ t0.68−0.72, where t is dewetting time. The slip behavior seems to be dominated by the viscous friction between the PMMA films and the SAM. As t increased, slip behavior disappeared, R ∝ t0.34−0.39. At surface energy of >42.0 mJ/m2, the PMMA films did not show slip behavior, R ∝ t0.45. It means that interface effects between PMMA films and SAM layers increase with increasing of γ of SAM layers, and then the molecular interaction in the PMMA films increases. The spreading coefficient (S) of the PMMA films approached positive number for UV exposure times between 0 s and 300 s. We concluded that the stability of the PMMA films can be simply controlled by UV-ozone treatment on the SAM layers.

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