Superhydrophobic Surfaces Formed Using Layer-by-Layer Self-Assembly with Aminated Multiwall Carbon Nanotubes

• Published in: Langmuir Vol. 24; no. 8; pp. 4245 - 4253
• Main Authors: Liao, Kang-Shyang, Wan, Albert, Batteas, James D, Bergbreiter, David E
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.04.2008
• Subjects: Chemistry; Colloidal state and disperse state; Emulsions. Microemulsions. Foams; Exact sciences and technology; General and physical chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Surface physical chemistry; Water; Self assembly; Atomic force microscopy; Polyethylene; Film; Nanoparticle; Acrylic acid; Surface layer; Thermogravimetry; Carbon nanotubes; Confocal microscopy; Contact angle; Powder; Thin film; Amine; Emulsion; Multiwalled nanotube; N,N-Dimethylformamide; Distribution; pH; Nanocomposite; Anchoring; Deposition
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la703730b

A convenient and simple route to functionalized multiwall carbon nanotubes (MWNTs) using the reaction of the amine (NH) groups of polyethyleneimine (PEI) with MWNTs in N,N-dimethylformamide (DMF) at 50 °C is described. The product functionalized MWNTs (MWNT-NH-PEI) contain 6−8% by weight PEI based on elemental analysis, thermal gravimetric analysis, and titration. The products form stable emulsions in water below pH 9 and can be derivatized to form alkylated MWNTs that are dispersible in organic media. Such MWNT-NH-PEI nanoparticles can also be used in covalent or ionic layer-by-layer assembly to form nanocomposite thin films on functionalized polyethylene (PE) films and powders. Such nanocomposite films were analyzed by contact angle analysis, atomic force microscopy (AFM), and confocal Raman microscopy. These analyses show that these superhydrophilic surfaces have micro/nanoroughness with a roughly uniform distribution of MWNT nanoparticles. Superhydrophobic PE films can be formed either from ionic layer-by-layer self-assembly of MWNT-NH-PEIs and poly(acrylic acid) or from covalent layer-by-layer self-assembly of MWNT-NH-PEIs and Gantrez if the final graft is acrylated with a mixed anhydride prepared from ethyl chloroformate and octadecanoic acid. The resulting octadecylated surface produced by five covalent layer-by-layer deposition steps has a water contact angle of 165° and a sliding angle of less than 5°. The corresponding surface produced by five ionic layer-by-layer deposition steps has a water contact angle of 155° but exhibits water pinning. The ionically assembled nanocomposite graft is labile under acidic conditions. The covalently assembled graft is more chemically robust.