Interfacial Properties of Fully Condensed Functional Silsesquioxane: A Langmuir Monolayer Study

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• 作者：Katarzyna Dopierala ; Anna Wamke ; Micha艂 Dutkiewicz ; Hieronim Maciejewski ; Krystyna Prochaska
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：October 23, 2014
• 年：2014
• 卷：118
• 期：42
• 页码：24548-24555
• 全文大小：398K
• ISSN：1932-7455

文摘

We have studied interfacial properties of fully condensed octakis[{2-(3,4-epoxycyclohexyl)etyl}dimethylsilyloxy]octasilsesquioxane (OE-POSS). The surface pressure鈥揳rea isotherm obtained in a Langmuir trough together with Brewster angle microscopy indicated formation of a stable, homogeneous liquid-like monolayer. For low molecular areas, the monolayer undergoes a stepwise collapse showing unusual multilayer morphology. A collapse mechanism is proposed to be a consequence of progressive decrease in the distance between silicon鈥搊xygen cages after reorganization of side groups. Hysteresis experiment showed incomplete respreading of small aggregates and successive decrease in molecular areas. Relaxation measurements indicated a slight impact of desorption and molecular rearrangements on the monolayer stability. Interfacial rheology was investigated for compressional deformation of the air/water interface. Both components of surface dilational modulus (elastic, E鈥? and viscous, E鈥? were determined by the oscillating barriers method. With increasing frequency, E鈥?decreased while E鈥?increased almost linearly. The loss angle tangent indicated elastic response of the monolayer in the range of low deformation rates and viscous behavior when subjected to fast deformation. The rheological behavior of the monolayer is also strongly affected by the collapse mechanism that begins at 20 mN/m.