Suppression of Dewetting in Nanoparticle-Filled Polymer Films

Abstract

The perturbing influence of nanosize filler particles on the dewetting of spun-cast polymer films is investigated. Previous studies have shown that spun-cast films of unentangled polystyrene (PS) and polybutadiene (PB) dewet acid-cleaned silicon wafers when the films are annealed above their bulk glass transition temperature T g. It is also known that "impurity" particles tend to promote dewetting in thin polymer films. Here we demonstrate that the addition of a small amount of C60 fullerene nanoparticles to the spin-casting polymer solution leads to an inhibition of dewetting in thin (L < 100 nm) PS and PB films cast on both acid-cleaned and carbon-coated silicon wafer substrates. Neutron reflection measurements indicate that this effect is associated with the formation of a diffuse fullerene layer near the solid substrate. Evidently, the immobilized fullerene particles form an enrichment layer at the solid boundary and "pin" the contact line of the growing dewetted ("dry") regions so that hole growth in the filled films becomes arrested at a scale which diminishes with increasing filler concentration. Above a relative fillerpolymer mass fraction of 1%, we no longer observe hole formation by atomic force microscopy on the time scales of our measurements (typically on the order of hours), suggesting the existence of a critical filler surface coverage for the suppression of dewetting. The roughness of the fullerene layer probably also contributes to the modification of the surface wetting properties through a change in the surface energy of the substrate, as suggested by recent measurements on substrates "roughened" by other means such as irradiation of polymer film substrates, grafting of polymer chains, etc.

Ultrathin liquid films under alternating intermolecular potential fields and capillary force

“…While there has been no result reported on the formation of ultrathin liquid films that are stable, there have been several studies reported for the stability of thin polymer films, involving the use of grafting [20][21][22] and nanoparticles. 23 However, the film thickness is on the order of 100 nm, whereas the thickness of the stable film in this study is on the order of 1 nm.…”

Resolving fundamental limits of adhesive bonding in microfabrication.

“…Here, we show that the addition of fullerenes [15] (C 60 ) to both PECH and BSP3 inhibits dewetting of thin polymer films. In Figure 3 In Figure 3-3, fullerenes were added to the same solution of PECH as above and then spin-coated.…”

“…As a sample calculation, consider a chain with N = 20 sites of diameter σ = 6.65 Å (using N = M/m o , this corresponds to PS with molecular weight 2040, a fairly short chain but about the same length as those used by Barnes et al [20]), and nanoparticles with diameter 1.5 σ ≈ 10 Å, i.e. 1 nm.…”

Nanostructures in Physical Materials Chemistry: An Exploratory Laboratory

“…The syntheses of nanometersized components have extended beyond carbon [2,10,[16][17][18][19][20]. A drawback to the utilization of carbon nanotubes, based on conductivity, is the inability to control the chirality.…”

“…Poly(2-methoxy-5-ethylhexyloxy-1,4-phenylene vinylene) (MEH-PPV)/rutile-TiO 2 composite films were made by Kim [19] with various sizes from 7 to 23 nm and their electroluminescent characteristics were investigated. Barnes [20] investigated the perturbing influence of nanosize filler particles on the dewetting of spun-cast polymer films. Rotkin [21] developed a new heuristic model for the calculation of the formation energy of the carbon nanoclusters.…”