(640i) Nanoscopic Wrinkled Morphology of Polyelectrolyte Multilayer Films on Poly(Dimethylsiloxane) Substrates Induced by Thermal Crosslinking

Layer-by-layer assembly of polyelectrolyte multilayer (PEM) thin films can be used to significantly alter surface properties and control the chemical functionality of a surface. The alternate adsorption of oppositely charged poly-ion molecules creates an ultra thin film that has different properties than the substrate surface. Nanoscopic morphology of PEM thin films assembled on top of poly(dimethylsiloxane) (PDMS) substrates can be irreversibly controlled with a permanent buckling instability induced by thermal crosslinking. The buckling instability is caused by a thermal expansion mismatch between the PEM film and PDMS substrate and resulted in a wavelike PEM film morphology that is not observed on glass or silicon substrates. The effect of altering the film morphology (i.e. thickness and porosity) before thermal crosslinking was also studied. The multilayer samples were characterized using optical microscopy, atomic force microscopy and spectroscopic ellipsometry. Using the strain-induced elastic buckling instability for mechanical measurements technique the Young's modulus of the PEM films was ascertained.