Structural Evolution Of Thin Polystyrene Films In Solvent Atmospheres

Thin polymer films have a high application potential in lithography, protectivecoating, selective filter film, photo-electric apparatus, data storage, micro-reactor andso on. Thin polymer film is also an ideal mode system for the study of lowdimensional physics because of its low vapor pressure and low mobility, which ishelpful for the development of low dimensional condensed physics. In recent years,many scientists have widely investigated thin polymer films. However, the stability ofthin polymer film is an important factor to influence its application, the study of thestructural evolution of thin polymer film has an important significance on basic sciences andtechnological applications. In this work, we use spectroscopic ellipsometer, optical microscopyand atomic force microscopy to investigate the structural evolution of polystyrene thin films.We designed and constructed an ellipsometric solvent cell to trace the kineticprocess of structural evolution of polystyrene films under solvent/nonsolventtreatment. The results showed that there was almost no considerable change in thesurface morphology of polystyrene films in solvent/nonsolvent atmospheres. Thethickness of the films, however, showed a nonlinear increase with time. The swollenfilms therefore reverted to the initial state after treatment. This might due to the factthat the gas in the cell was a mixture and the partial pressure of the non-solvent wasnot high enough to induce the precipitation of the polystyrene chains.Based on the results of the ellipsometry online experiment, we used opticalmicroscopy to observe the in-situ structural evolution of the polystyrene films. Theresult showed that the films swelled gradually as time increase and finally reached astatic state, and experienced a dewetting phenomenon.