Effect of Porogen Molecular Architecture and Loading on Structure of Porous Thin Films

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• 作者：Hae-Jeong Lee ; Christopher L. Soles ; Bryan D. Vogt ; Da-Wei Liu ; Wen-li Wu ; Eric K. LinHo-Cheol Kim ; Victor Y. Lee ; Willi Volksen ; Robert D. Miller
• 刊名：Chemistry of Materials
• 出版年：2008
• 出版时间：December 23, 2008
• 年：2008
• 卷：20
• 期：24
• 页码：7390-7398
• 全文大小：415K
• 年卷期：v.20,no.24(December 23, 2008)
• ISSN：1520-5002

文摘

The effects of molecular architecture and loading of a porogen material on the structural characteristics of methylsilsesquioxane (MSQ)-based porous films are examined using X-ray porosimetry (XRP) and small-angle neutron scattering (SANS). Either linear (NG) or star-shaped (TP) polymers are used as the porogen here and blended with the MSQ material at loadings from 20 to 50% by mass, resulting in porosities between 30 and 60% by volume, regardless of porogen architecture. This indicates that the MSQ matrix material contains approximately 10% by volume inherent microporosity. The average pore size increases with increased porogen loadings in a way that depends on the porogen architecture. The NG porogen tends to aggregate, more than tripling the average pore size as the porogen loading increases from 20 to 50% by mass (22 to 76 Å in diameter). By contrast, the TP porogen has less propensity to aggregate, leading to a smaller increase in terms of percent change in the average pore size for the same porogen loading range (76 to 132 Å in diameter). Changes in the porogen type or loading do not influence the wall density (1.47 ± 0.01) g/cm³ of the material between the pores, whereas the coefficient of thermal expansion (CTE) is approximately 1.5 times greater for the NG samples than for the TP samples at all porogen loadings.