Enhancing the stability of polystyrene ultrathin films by using star-shape polymers as dewetting inhibitors

This contribution introduces a new class of materials for improving the stability of polystyrene (PS) ultrathin films. Two types of three-arm polystyrenes (TA-PS) with different arm lengths are added into PS thin films with thicknesses of 7 and 23 nm. Concentration of the TA-PS additives is varied from 0 to 40 wt%. The morphological change of PS films upon annealing above its glass transition temperature is followed by utilizing optical and atomic force microscopy. Our results show that the addition of TA-PS into PS films leads to significant improvement of the film stability. The dewetting rate of PS film containing only 5 wt% of TA-PS is 3 times slower than that of the pure PS film. The increase of TA-PS concentration results in systematic decrease of the dewetting rate. We also observe that the dewetting-suppression efficiency of the TA-PS depends significantly on its arm length.