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

Previous studies have shown that spun-cast films of unentangled synthetic p olymers commonly dewet inorganic or organic substrates, leading to technolo gically detrimental results for many applications. We illustrate two strate gies for influencing polymer film dewetting on inorganic and organic substr ates. First, the addition of small amounts of C-60 fullerene nanoparticles to the spin-casting polymer solutions of model synthetic polymers [polystyr ene (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 dewetti ng 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 hyperg raft (a comb polymer) and a G2 hyper-graft (resembling a spherical 'micro-g el' particle). The late stage of dewetting in the G2 films, however, differ s significantly from the low generation films because of an inhibition of h ole coalescence in the intermediate stage of film dewetting. This behavior resembles previous observations of dewetting in 'entangled' polystyrene fil ms. Thus, the viscoelasticity of the polymer film can have an inhibitory ef fect 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.