Influence of nanoparticles and polymer branching on the dewetting of polymer films

Previous studies have shown that spun-cast films of unentangled synthetic polymers commonly dewet inorganic or organic substrates, leading to technologically detrimental results for many applications. We illustrate two strategies for influencing polymer film dewetting on inorganic and organic substrates. First, the addition of small amounts of C-60 fullerene nanoparticles to the spin-casting polymer solutions of model synthetic polymers [polystyrene (PS) and polybutadiene (PB)] leads to a significant inhibition of film dewetting on Si. This effect is associated with the formation of a diffuse fullerene layer near the solid substrate that frustrates the dewetting hole growth process. Next, we consider polymer branching effects on the dewetting of various generations of hypergraft polymer poly(2-ethyl-2-oxazoline) (PEOX) films cast on high molecular weight polystyrene substrates. The early stage of dewetting is found to be similar in a zeroth generation GO hypergraft (a comb polymer) and a G2 hyper-graft (resembling a spherical 'micro-gel' particle). The late stage of dewetting in the G2 films, however, differs significantly from the low generation films because of an inhibition of hole coalescence in the intermediate stage of film dewetting. This behavior resembles previous observations of dewetting in 'entangled' polystyrene films. Thus, the viscoelasticity of the polymer film can have an inhibitory effect on film dewetting, leading to changes in the dewetted film morphology rather than a suppression of film dewetting. (C) 2001 Elsevier Science B.V. All rights reserved.