Influence of film structure on the dewetting kinetics of thin polymer films in the solvent annealing process

Abstract

On a non-wetting solid substrate, the solvent annealing process of a thin polymer film includes the swelling process and the dewetting process. Owing to difficulties in the in situ analysis of the two processes simultaneously, a quantitative study on the solvent annealing process of thin polymer films on the non-wetting solid substrate is extremely rare. In this paper, we design an experimental method by combining spectroscopic ellipsometry with optical microscopy to achieve the simultaneous in situ study. Using this method, we investigate the influence of the structure of swollen film on its dewetting kinetics during the solvent annealing process. The results show that for a thin PS film with low M_w (M_w = 4.1 kg mol⁻¹), acetone molecules can form an ultrathin enriched layer between the PS film and the solid substrate during the swelling process. The presence of the acetone enriched layer accounts for the exponential kinetic behavior in the case of a thin PS film with low M_w. However, the acetone enriched layer is not observed in the case of a thin PS film with high M_w (M_w = 400 kg mol⁻¹) and the slippage effect of polymer chains is valid during the dewetting process.