Dewetting of Stable Thin Polymer Films Induced by a Poor Solvent: Role of Polar Interactions

Abstract

We investigate the room temperature instability and dewetting of ultrathin (<100 nm) stable polystyrene (PS) films induced by a poor solvent, such as acetone, on a higher energy silicon substrate without an oxide layer. Instability behavior is contrasted for thermal annealing and acetone-vapor annealing and by immersion under liquid acetone. The PS films that are stable under thermal annealing are rendered unstable to dewetting when contacted by acetone, notwithstanding the stabilizing apolar van der Waals interactions in all the three systems. Relatively high molecular weight films dewet only in the liquid acetone, but low molecular weight films dewet on contact with both vapor and liquid acetone. These findings indicate the role of polar interactions engendered by acetone in the film instability modified possibly by nanophase separation aided by the substrate and nucleative mechanisms. Liquid acetone greatly enhances the instability so that the number density of holes produced in liquid acetone is about 2 orders higher than in acetone vapor. In both of these cases, the scaling (N ∼ H n ) of the number of holes per unit area, N, with the film thickness, H, is found to be clearly different (n ∼ 2.5–2.7) from that seen in most of the previous studies on thermal dewetting (n ∼ 4). From the kinetics of hole growth, the slippage effect of PS chains can be observed in the solvent vapor-induced dewetting process but not in the dewetting under liquid acetone.

Polymer Film Dewetting by Water/Surfactant/Good‐Solvent Mixtures: A Mechanistic Insight and Its Implications for the Conservation of Cultural Heritage

“…The interaction between NSFs and polymer thick films involves dewetting . It is known that dewetting of thin polymer films (<100 nm) can be induced by thermal annealing, exposure to vapors of the solvents, immersion in poor solvents, in water/solvent mixtures or, finally, in non‐solvents . We observed that the presence of amphiphiles in a water/good‐solvent mixture can be key for dewetting thick polymer films from surfaces.…”

Swelling, dewetting and breakup in thin polymer films for cultural heritage

“…The tendency to de-wet is clearly set by the unstable nature of the system concerning short-range wetting forces: The SiO 2 covered substrate is partially hydrophilic and it would be energetically more favorable to be covered by water rather than the hydrophobic LA. The role of polar forces in de-wetting of thin polymer films by immersion in poor solvents 64 or non solvent/poor solvent mixtures 65 was already pointed out with polystyrene films supported by silicon wafers. If the size of these defects is smaller than the in-plane neutron coherence length the NR spectra will still fit reasonably to a 3 slab polymer model but additionally diffuse scattering might appear if the SLD contrast and the surface coverage are big enough.…”

Enhanced Self-Organized Dewetting of Ultrathin Polymer Blend Film for Large-Area Fabrication of SERS Substrate

“…We have earlier shown that owing to closely matched van der Waals properties of PS and organic solutions, the net apolar van der Waals force in such systems is negligible or even slightly stabilizing53. The genesis of thin polymer film instability is thus traced to the polar interactions induced by the presence of organic solvent.…”