Dewetting dynamics in miscible polymer-polymer thin film mixtures

Area of Science:

• Materials Science
• Polymer Physics
• Thin Film Dynamics

Background:

• Thin polystyrene films on oxidized silicon substrates can become unstable and dewet upon heating above their glass transition temperature.
• Hole nucleation and growth driven by capillary forces are characteristic of dewetting in metastable thin films.
• Incorporating a second component, like a copolymer or miscible polymer, has been shown to enhance film stability and suppress dewetting.

Purpose of the Study:

• To investigate the effect of adding tetramethyl bisphenol-A polycarbonate (TMPC) on the dewetting behavior of thin polystyrene films.
• To analyze the hole growth dynamics and morphology in polystyrene/TMPC mixtures on SiOx/Si substrates.
• To elucidate the mechanisms responsible for dewetting suppression in these polymer blends.

Main Methods:

• Fabrication of thin films composed of polystyrene and TMPC mixtures on oxidized silicon substrates.
• Experimental observation and analysis of hole nucleation and growth dynamics.
• Rheological characterization through dewetting dynamics to determine viscosity and glass transition behavior.

Main Results:

• Hole growth velocity significantly decreased with increasing TMPC content.
• The suppression of dewetting velocity was attributed to reduced capillary driving forces and increased substrate-polymer interfacial friction.
• Viscosity, derived from hole growth, decreased with film thickness, correlating with a depression of the glass transition temperature.

Conclusions:

• Tetramethyl bisphenol-A polycarbonate effectively stabilizes thin polystyrene films against dewetting.
• The stabilization mechanism involves both thermodynamic (reduced capillary driving force) and kinetic (increased interfacial friction) factors.
• Film thickness influences viscosity and glass transition temperature, impacting overall film stability.