Enhanced Delamination of Ultrathin Free-Standing Polymer Films via Self-Limiting Surface Modification

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• 作者：Salmaan H. Baxamusa ; Michael Stadermann ; Chantel Aracne-Ruddle ; Art J. Nelson ; Maverick Chea ; Shuali Li ; Kelly Youngblood ; Tayyab I. Suratwala
• 刊名：Langmuir
• 出版年：2014
• 出版时间：May 13, 2014
• 年：2014
• 卷：30
• 期：18
• 页码：5126-5132
• 全文大小：309K
• 年卷期：v.30,no.18(May 13, 2014)
• ISSN：1520-5827

文摘

Free-standing polymer thin films are typically fabricated using a sacrificial underlayer (between the film and its deposition substrate) or overlayer (on top of the film to assist peeling) in order to facilitate removal of the thin film from its deposition substrate. We show the direct delamination of extraordinarily thin (as thin as 8 nm) films of poly(vinyl formal) (PVF), polystyrene, and poly(methyl methacrylate). Large (up to 13 cm diameter) films of PVF could be captured on wire supports to produce free-standing films. By modifying the substrate to lower the interfacial energy resisting film鈥搒ubstrate separation, the conditions for spontaneous delamination are satisfied even for very thin films. The substrate modification is based on the electrostatic adsorption of a cationic polyelectrolyte. Eliminating the use of sacrificial materials and instead relying on naturally self-limiting adsorption makes this method suitable for large areas. We have observed delamination of films with aspect ratios (ratio of lateral dimension between supports to thickness) of 10⁷ and have captured dry, free-standing films with aspect ratios >10⁶. Films with an aspect ratio of 10⁵ can bear loads up to 10⁶ times the mass of the film itself. The presence of the adsorbed layer can be observed using X-ray photoelectron spectroscopy, and this layer is persistent through multiple uses. In the system studied, elimination of sacrificial materials leads to an enhancement in the failure strength of the free-standing thin film. The robustness, persistence, and the self-optimizing nature distinguish this method from various fabrication methods utilizing sacrificial materials and make it a potentially scalable process for the fabrication of ultrathin free-standing or transferrable films for filtration, MEMS, or tissue engineering applications.