Molecular electronics is often limited by the poorly defined nature of the contact between the molecules and the metal surface. We describe a method to wire molecules into gaps in single-walled carbon nanotubes (SWNTs). Precise oxidative cutting of a SWNT produces carboxylic acid-terminated electrodes separated by gaps of =10 nanometers. These point contacts react with molecules derivatized with amines to form molecular bridges held in place by amide linkages. These chemical contacts are robust and allow a wide variety of molecules to be tested electrically. In addition to testing molecular wires, we show how to install functionality in the molecular backbone that allows the conductance of the single-molecule bridges to switch with pH.
Multiarmed, cardanol-based acrylate oligomers were prepared via the ring-opening reaction between cardanyl glycidyl ether (CGE) and polyacids, followed by epoxidization of the unsaturation in alkyl side chains of cardanol segments, and acrylation of the resulting epoxy groups. Biobased coatings were produced from UV-radiation-initiated curing of these acrylates; the coating properties were then characterized in detail. The acrylate oligomers were fully characterized using gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance ( 1 H NMR). The UV-curing behavior of these acrylates was determined using real-time IR. The results indicated that the conversion of acrylate unsaturation increased with increasing oligomer functionality. These oligomers were formulated into UV-curable coatings, and the coating properties were evaluated to determine hardness, adhesion, chemical resistance, gloss, and surface properties. The properties of cured thermosets were also studied using tensile testing, dynamic mechanical thermal analysis (DMTA), and thermogravimetric analysis (TGA). Compared to coating from benchmark biobased UV-curable oligomer, acrylated epoxidized soybean oil (ASBO), cardanol-based coatings showed higher hardness, excellent adhesion, and enhanced thermal and mechanical properties while maintaining reasonably high biorenewable contents. These improvements in coating performances can be contributed to their unique oligomer architectures that combined the structural features of rigid benzene ring, long flexible alkyl chains, and polar hydroxyl groups.
Colorless polyimides with excellent thermal and mechanical properties were developed from 2R,5R,7S,10S-naphthanetetracarboxylic dianhydride, and their properties were systematically compared with those based on 1S,2R,4S,5R-cyclohexanetetracarboxylic dianhydride.
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