| Carbon nanotubes have demonstrated a wealth of exceptional structure, mechanical and electronic properties, which have made them potentially useful for application in nano-composites. The hybrid materials based on carbon nanotubes have become an area of significant interest in rectent years.Water soluble multiwall carbon nanotube (MWNT) was prepared via chemical oxidation. Hydrogels composed of acrylic acid, acrylamide and MWNT were in-situ synthesized. The sensitivities of the hydrogels to pH, temperature, ionic strength and were investigated. The weight of wet hydrogel in pure water is about 200 times to the weght of dry hydrogel. And the SR of the hydrogel in alkaling weak solution is about 20 times to it in acidic solution. On the other hand, the bending characteristics of hydrogels were studied under the d.c.electric fields. The mechanism of the MWNT combining with the copolymer of acrylic acid and acrylamide was discussed. The weak intermolecular adsorption may play an important role in the combination between the MWNT and the copolymer.Composite multilayer films of the oxidized MWNTs and poly (ethyleneimine) (PEI) were fabricated through the layer-by-layer (LbL) assembly approach. The LbL assembly process of the multilayer films was monitored with a UV-vis spectrophotometer. The surface and section morphologies of the films were observed under a Schottky field emission scanning electron microscope. On the thin films of 12x25 mm, two parallel metal electrodes of 2x20 mm with a spacing of 2 mm were vapor deposited. The resistance between the two electrodes was measured at different relative humidity levels at room temperature. The data show that the resistance increases with relative humidity over the range of 5%~97% RH and that, in the range of 5%~85% RH, the resistance increases almost linearly. The experimental data also show that the humidity sensitive multilayer films have response and recovery times of about 2 s and 30 s respectively.
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