Polymer thin film stability has important fundamental and technological implications. Recently, we established that poly(vinyl alcohol) (PVOH) spontaneously adsorbs to polydimethylsiloxane (PDMS) substrates from aqueous solution. The stability of the PVOH thin films can be controlled by the substrate mobility or PDMS molecular weight/thickness. The dewetting patterns vary from conventional droplets to unique fractal features. They are irregular, however, due to the non-uniform drying across the thin film samples. In this research, adsorptive spin casting is evaluated as a new method that combines the spontaneity of polymer adsorption and controlled directional drying. Specifically, PVOH thin film morphologies are evaluated under various conditions, including adsorption/contact time, PVOH drop size, and spin rate. Ordered fractal morphologies are produced within a confined drop as the result of directional drying in a circular geometry and in the runoff region as the result of directional drying in a linear geometry. Fractal morphology is imaged using optical microscopy. Sectional images are then merged into an image of the entire sample using either Photomerge in Photoshop or Autopano Giga. Fractal dimension and lacunarity of each image are determined using the Fraclac plugin in ImageJ. The formation of the fractal morphology appears to be in the reverse direction of diffusion limited aggregation.

Poly(vinyl alcohol) thin film dewetting on polydimethylsiloxane surfaces by directional drying

255th National Meeting (2018)

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