Effect of polystyrene molecular weight and zinc oxide concentration on dewetting behavior of polymeric thin films

Abstract

The separation between ultra-thin polymer film on metal oxide substrate is called dewetting. Dewetting causes the polymer films to loss their stability and other important properties, for example, the films may short circuit or reduce their transparency. Therefore, the stability of polymer thin films on substrate need to be improved. Addition of nanoparticles is one of the most popular technique used to increase the stability of polymer thin films. The correlation between the different of molecular weight and ZnO concentration on dewetting behavior was studied in this research. The appropriate concentration of ZnO on dewetting suppression in each molecular weight was examined. Furthermore, the variation of dewetting pattern in each molecular weight system was analyzed. In this research, PS (13K and 30K) solutions mixed with ZnO suspension in toluene were prepared. The concentrations of ZnO in PS solution were 0-1.0 wt%. All composite thin films were coated by spin-casting technique and annealed at a temperature of 100°C in a vacuum oven to induce dewetting behavior. The topographies of annealed thin films were studied by using Optical microscope (OM) and Scanning electron microscope (SEM). The thicknesses of thin films were examined by Atomic force microscope (AFM). The surface energies of PS and PS-ZnO composite films were measured and calculated by using contact angle measurement. From the results, we found that addition of ZnO nanoparticles at concentrations 0.7 and 1.0 wt% are the optimum concentration for dewetting inhibition of PS13K and PS30K films, respectively.