Preparation of Ultrathin Silsesquioxane Nanofilms via Polymer Langmuir−Blodgett Films
journal contributionposted on 2008-07-08, 00:00 authored by Masaya Mitsuishi, Feng Zhao, Yeji Kim, Akira Watanabe, Tokuji Miyashita
This Article describes a unique approach to building silsesquioxane nanoassemblies based on the Langmuir−Blodgett (LB) technique. Poly(N-dodecylacrylamide-co-3-methacryloxypropyl-T8-heptatrifluoropropyl (or heptaphenylpropyl) POSS)s (p(DDA/SQ)s) were synthesized through free radical copolymerization using propyl methacrylate-substituted polyhedral oligomeric silsesquioxane (POSS) monomers containing seven nonreactive trifluoropropyl or phenyl groups (R7(Si8O12)(CH2CH2CH2OCOCH3CCH2) (where R is either trifluoropropyl (SQF) or phenyl (SQPh)) and amphiphilic copolymers. The p(DDA/SQ)s formed stable monolayers at the air/water interface. The monolayers were transferred onto solid substrates as Y-type LB films using a vertical dipping method. The polymer LB films had a well-defined layer structure and a surface flatness (rms values < 1 nm in 1 μm2). The high heat-resistant properties of the p(DDA/SQ) LB films were demonstrated using UV−vis spectroscopic reflectometry and FT-IR. The refractive index and the thickness of the p(DDA/SQ) LB films were measured as functions of temperature. Upon heating, the refractive index of the p(DDA/SQPh) LB films increased from 1.43 (200 °C) to 1.49 (270 °C), whereas that of poly(N-dodecylacrylamide) (pDDA) decreased from 1.38 (200 °C) to 1.28 (220 °C), indicating a densely packed configuration of silsesquioxane units in thin films. A control experiment with pDDA LB films showed domain structures at temperatures greater than 200 °C, although the p(DDA/SQ) LB films remained uniform and smooth after heating to 320 °C. This bottom-up approach is promising for coating with organic and inorganic nanomaterials for optoelectric nanodevice applications.
silsesquioxane unitspDDA LB films1 nmSQFoptoelectric nanodevice applicationspolymer LB filmsPOSSUVbuilding silsesquioxane nanoassembliesUltrathin Silsesquioxane Nanofilmscontrol experimentamphiphilic copolymerslayer structurerms valuessurface flatnessdomain structuresnonreactive trifluoropropylphenyl groups