|M.Sc Student||Golany Ziv|
|Subject||Dewetting of Polymer Films in Non-Solvent-Solvent|
Environment: New Approach for Polymer Patterning
|Department||Department of Nanoscience and Nanotechnology||Supervisor||DR. Tamar Segal-Peretz|
|Full Thesis text|
Dewetting of polymers is a central phenomenon in polymer thin films which can affect films’ stability and morphology. In many polymers thin film application dewetting is undesired. However, dewetting can also be harnessed for patterning micro and nano features with controlled dimensions and order. Dewetting of polymer thin film occurs due to the film’s instability and typically begins with the film rupture and formation of holes; the holes continue to grow until they collapse and create small droplets. The phenomenon of dewetting induced by thermal treatment or solvent vapors has been studied extensively in a variety of polymers over the past years. Unlike these common dewetting paths, there is a knowledge gap in the field of dewetting of thin polymer films in an environment that combines both solvent and non-solvent. In this research, the dewetting process of polystyrene and poly(methyl methacrylate) thin films was studied after immersing the polymer films in a non-solvent, and exposure to solvent vapors, creating a solvent - non-solvent environment. In such systems, the non-solvent presence increases the destabilizing force and reduces the spreading parameter, causing changes in the dewetting rate and in the polymer's final morphology. In solvent - non-solvent environment the dewetting rate is extremely fast and ends with significantly lower dimensions of the polymer droplets compared to polymer film dewetting under solvent vapors or thermal treatment. In addition, the final contact angle of the polymer with the substrate is considerably higher, which gives the droplets a spherical structure. With the knowledge obtained on polymer dewetting in a solvent - non-solvent environment, a simple low-cost process was introduced to enable fabrication of long-range order polymer sphere patterns in macro- and nano-scales. The process, which is based on directed polymer solution evaporation to form polymer lines, followed by dewetting, is spontaneous and does not require any manipulation on the substrate surface. Sequential infiltration synthesis was then utilized to selectively grow inorganic materials within the polymer spheres, forming hybrid and inorganic structures, thereby giving functionality and stability to the aligned patterns.