Stability and Dewetting of Metal Nanoparticle Filled Thin Polymer Films: Control of Instability Length Scale and Dynamics

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• 作者：Rabibrata Mukherjee ; Soma Das ; Anindya Das ; Satinder K. Sharma ; Arup K. Raychaudhuri ; Ashutosh Sharma
• 刊名：ACS Nano
• 出版年：2010
• 出版时间：July 27, 2010
• 年：2010
• 卷：4
• 期：7
• 页码：3709-3724
• 全文大小：690K
• 年卷期：0
• ISSN：1936-086X

文摘

We investigate the influence of gold nanoparticle addition on the stability, dewetting, and pattern formation in ultrathin polymer−nanoparticle (NP) composite films by examining the length and time scales of instability, morphology, and dynamics of dewetting. For these 10−50 nm thick (h) polystyrene (PS) thin films containing uncapped gold nanoparticles (diameter ∼3−4 nm), transitions from complete dewetting to arrested dewetting to absolute stability were observed depending on the concentration of the particles. Experiments show the existence of three distinct stability regimes: regime 1, complete dewetting leading to droplet formation for nanoparticle concentration of 2% (w/w) or below; regime 2, partial dewetting leading to formation of arrested holes for NP concentrations in the range of 3−6%; and regime 3, complete inhibition of dewetting for NP concentrations of 7% and above. Major results are (a) length scale of instability, where λ_H ∼ hⁿ remains unchanged with NP concentration in regime 1 (n ∼ 2) but increases in regime 2 with a change in the scaling relation (n ∼ 3−3.5); (b) dynamics of instability and dewetting becomes progressively sluggish with an increase in the NP concentration; (c) there are distinct regimes of dewetting velocity at low NP concentrations; (d) force modulation AFM, as well as micro-Raman analysis, shows phase separation and aggregation of the gold nanoparticles within each dewetted polymer droplet leading to the formation of a metal core−polymer shell morphology. The polymer shell could be removed by washing in a selective solvent, thus exposing an array of bare gold nanoparticle aggregates.