Interplay of Substrate Surface Energy and Nanoparticle Concentration in Suppressing Polymer Thin Film Dewetting

Abstract

It is known that dewetting of a polystyrene (PS) thin film on a silicon substrate gets completely suppressed upon addition of small amount of C 60 nanoparticles (NP). 1 The NPs migrate to the film−substrate interface and forms an enriched surface layer of the particles that eventually stabilizes the film by apparent pinning. In this article we quantitatively highlight the unexplored effect of substrate surface energy (γ S ) on the migration of the NPs to the film−substrate interface and their contribution on dewetting suppression. Depending on the relative magnitudes of NP concentration (C NP ) and γ S , we identify three distinct stability regimes. In regime 1 (C NP < 0.2%) there is no suppression of dewetting and the final polygonal arrangement of droplets closely resemble dewetted structures in particle free films. However, the size of the polygons becomes smaller in NP containing films when γ S < γ C60 (NP surface energy) and larger as γ S exceeds γ C60 . In regime 2 (0.3% < C NP < 0.75%) the films dewet partially, and the extent of dewetting is seen to strongly dependent on the relative magnitudes of γ C60 and γ S . While dewetting proceeds up to the stage of partial hole growth and coalescence when γ S < γ C60 , some random isolated holes are seen to form when γ S > γ C60 . On the basis of direct AFM imaging, we show that in both regimes 1 and 2 the NPs migrate to the substrate−film interface only when γ S > γ C60 . We show complete suppression of dewetting in regime 3 (C NP > 1.0%), where the particles are seen to migrate to the substrate for all values of γ S . The work highlights that entropy driven migration of particles takes place on substrates with any γ S only above a critical NP concentration (C NPC ) and only on substrates with γ S > γ C60 when C NP < C NPC . The findings, apart from dewetting suppressing, can guide potential design criteria for applications such as electron extracting layer in organic photovoltaic.

Fabrication of Biomimetic Micropatterned Surfaces by Sol–Gel Dewetting

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Design and application of discontinuous resin distribution patterns for semi-pregs

“…The film is then heated, causing resin to recede from the nucleation sites. The resin recession is driven by the surface tension between the low surface energy substrate (the silicone-coated backing paper) and the resin [14][15][16][17]. The dewetted resin is transferred onto a fiber bed by briefly pressing the constituents in a hydraulic press.…”

Liquid–liquid interfacial slip induced layer instability in a thin polymer bilayer

“…Thin polymer film can become unstable and spontaneously rupture whenever the intermolecular disjoining pressure increases with increased film thickness [6][7][8][9][10][11][12][13][14][15][16][17] . The dewetting of thin polymer film progresses with the formation and growth of randomly placed holes with a certain mean length scale.…”