Precise analysis of coating defect formation on nanoparticles/polymer composite thin films

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17360371
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Properties in chemical engineering process/Transfer operation/Unit operation
• Research Institution: Osaka Prefecture University
• Principal Investigator: TSUKADA Takao Osaka Prefecture University, Graduate School of Engineering, Professor, 工学研究科, 教授 (10171969)
• Co-Investigator(Kenkyū-buntansha): ADSHIRI Tadafumi Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Professor, 多元物質科学研究所, 教授 (60182995) ; IMAISHI Nobuyuki Kyushu University, Institute for Materials Chemistry and Engineering, Professor, 先導物質化学研究所, 教授 (60034394)
• Project Period (FY): 2005 – 2006
• Keywords: nanoparticles / polymer / composite film / coating defect / precise analysis

Research Abstract

The ultimate aim of our work is to acquire correct understandings for the dewetting behavior of nanoparticles/polymer composite thin films in order to determine the optimum conditions for a defect-free and smooth coating of the films. In the present work, the following points were investigated as the first step.
The dewetting behavior of polystyrene (PS) thin films containing CeO_2 nanoparticles on a silica glass plate coated with octadecyltrietoxysilane was observed using a phase-shifting interference microscopy, a laser scanning confocal microscopy and an atomic force microscopy, where the PS film was spin coated on the silane-coated substrate, and then was annealed at 353 K. The surface of the CeO_2 nanoparticles used here were modified with decanoic acid through the organic-ligand-assisted supercritical hydrothermal process, and consequently, the nanoparticles obtained were cubic-shaped ones with average edge length of 4-6 nm and could be dispersed completely in organic solvents. Th e film thickness was approximately 20-30 nm. As a result, several holes, i.e., dry patches with a rim, caused by the dewetting process appeared on the PS film containing nanoparticles, expanded and approached one another. Then, the approaching holes became a bridging filament, and finally, broke and left behind isolated small droplets on the substrate. Also, it seemed that the dewetting process of the PS film containing nanoparticles was faster than that without nanoparticles, although we could not discuss quantitatively the comparison between the dewetting behaviors with and without nanoparticles because the dewetting behavior without nanoparticles at the initial stage could not be observed. It was found that the size of the small droplets left on the substrate became smaller when the nanoparticles were added.
In addition, numerical simulations of dewetting process based on the lubrication approximation were carried out, considering that the enhancement of dewetting by addition of nanoparticles was due to the variation of apparent Hamaker constant of the film.