Self-healing and dewetting dynamics of a polymer nanofilm on a smooth substrate: strategies for dewetting suppression

Abstract

The self-healing and dewetting dynamics of a polymer nanofilm on a smooth, partial wetting surface are explored by many-body dissipative particle dynamics. Three types of dewetting phenomena are identified, (i) spinodal decomposition, (ii) nucleation and growth, and (iii) metastable self-healing. The outcome depends on the surface wettability (θ_Y), the polymer film thickness (h₀), and the radius of the dry hole (R₀). The phase diagram of the dewetting mechanism as a function of θ_Y and h₀ is obtained for a specified R₀. As the surface wettability decreases (increasing θ_Y), the critical film thickness associated with the nucleation/self-healing crossover (h_c) grows so that the metastability of the film can be retained by the self-healing process. In addition to θ_Y and R₀, h_c depends on the polymer length (N) as well. It is found that a longer polymer requires a thicker nanofilm to avoid dewetting by nucleation. Two strategies for dewetting suppression are proposed. The metastability of a film of polymers with a large molecular weight can be promoted either by the addition of short polymers or by employing compact polymers such as star polymers. In the latter approach, the increment of the arm number enhances the nanofilm stability.