Polymer / Compatibilizer / Multi - Walled Carbon Nanotube Ternary Conductive Composite Material Preparation, Film Assembly And Characterization

Conductive materials are a cutting-edge research subject in the field of materials science, and an important research orientation of functional polymer materials. Conductive polymer composite materials (CPCs) have characteristics of light quality, high performance cost ratios and adjustable resistivity in a broad range, especially they are easy to be processed and assembled into solid state thin films required in most applications. Thus, they have widely used as electromagnetic shielding materials, fuel cells, and over current protection elements, especially chemical gas sensor materials. Most of polymers are insulative and conductive fillers need to be added. Carbon nanotubes (CNTs) possess nanoscale size, high length-diameter ratio, excellent electrical properties, mechanical properties and some surface adsorption performances, and thus become ideal conductive fillers. However, the van der waals forces of CNTs have affected its dispersion in the matrices and the interface binding between CNTs and matrices, which restrict their wide applications. Though the nitroxide-mediated controlled free-radical polymerization can get the CPCs with controlled molecular weight, low molecular weight distribution and good dispersion, the improvement of CNTs dispersion in the matrices and interface adhesive properties of CNTs and polymers is not remarkable. This study builds a bridge between CNTs and polymers by introducing compatibilizer in order to get stable multiphase conductive composite materials with good dispersion. This work includes the following two aspects:1. Polystyrene-block-poly(tert-butyl methacrylate)/multiwall carbon nanotubes (PS-b-P/BMA/MWNTs-COOH) conducting nanocomposites based on a compatibilizer, MWNTs-COOH graft PS-b-PtBMA, were prepared via a solution blending method. The PS-b-P/BMA and MWNTs-b-PtBMA-b-PS were synthesized by nitroxide-mediated controlled free-radical polymerization. The chemical structure and system composition were characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance (1H NMR), Raman spectroscopy and thermogravimetric analysis (TGA). The effect of the compatibilizer MWNTs-g-P/BMA-b-PS on the dispersion behavior and morphology of MWCNTs in the composite systems were investigated by UV-vis, scanning electron microscope (SEM) and transmission electron microscopy (TEM) etc.2. The conductive composite materials were fabricated into the thin films as sensing elements, and the response of the ternary conducting nanocomposite thin films to chloroform vapor was studied. The effect of the compositional ratios of MWNTs-COOH and MWNTs-g-PtBMA-b-PS, and the analyte concentrations on response patterns were investigated. The reusability of the ternary conductive gas sensitive thin films was examined in the same chloroform vapor concentration, and compared with the conductive gas-sensitive materials without compatibilizer. The experimental results showed that the response patterns were influenced by the compositional ratios of MWNTs-COOH and MWNTs-g-PtBMA-b-PS and the analyte concentrations. The conducting nanocomposite film sensors with compatibilizer exhibited excellent response, reproducibility and stability compared with that devoid of compatibilizer, and consequently they can be employed as a prospective candidate of chemical resistors or electronic noses for detection of chloroform vapor.