Preparation, Characterization And Gas-sensitive Response Performance Of Sensitive Conductive Polymer Composites

Rapidly increasing environmental pollution has been recognized as a major concern,so human imminently requires a minimal analytical tool to assess the environmental impact of organic pollutants with the increasing number of volatile organic compounds(VOCs)in environments.Conductive polymer composites(CPCs)attract widespread attention in the field of the environmental gas/vapor detection because of their unique physical and chemical properties.The CPCs that can respond to environmental stimuli are called sensitive conductive polymer composites(SCPCs).This kind of vapor sensitive materials can be fabricated into gas/vapor sensors or electronic noses rapidly responding to organic solvents or their vapors,thus being capable of effectively detecting the leakage of various environmental pollutants.Therefore,it is highly necessary to develop new SCPCs for fabrication of sensors to lessen or avoid the harm of chemical species in the indoor and outdoor environments to human health.Inspired by this idea,the following two aspects of work has been done in this paper:(1)Novel multiwalled carbon nanotube@polypyrrole coated with hydroxyl-terminated poly(butadiene-co-acrylonitile)polyurethane conductive polymer nanocomposites(MWCNTs@PPY/HTBN PU)were prepared via in situ stepwise polymerization,while the MWCNTs@PPY nanocomposites were prepared through an oxidative polymerization of polypyrrole(PPY)in the presence of carboxylated MWCNTs(MWCNTs-COOH).The chemical structure and compositions were characterized by Fourier transform infrared spectroscopy,Raman spectroscopy,X-ray diffraction,and thermogravimetry techniques,and the morphologies and dispersion behavior were observed by UV-vis spectrophotometer,scanning electron microscope and transmission electron microscope.The MWCNTs@PPY/HTBN PU nanocomposites were fabricated into thin film sensors to examine their response to CHCl3 vapor.The influence of the compositional ratios of MWCNTs-COOH to PPY and/or MWCNTs@PPY to the final composites on the conductivity and responsivity towards CHCl3 vapor was investigated.The experimental results indicated that modulating the system compositions could endow the film sensor from the resulting nanocomposites with high response intensities,good restorability,repeatability and stability,and a good linear relationship between responsivity and the CHCl3 vapor concentration in a wide range from 50 to 3000 ppm.Therefore,the prepared nanocomposites were proved to be capable of being fabricated into gas sensing elements for detection of environmental gaseous pollutants.(2)A novel nanocomposite that consists of polystyrene-block-chain-extended hydroxyl terminated polybutadiene-block-polystyrene(PS-b-HTPB5-b-PS)and multiwalled carbon nanotubes(MWCNTs)was designed and prepared via noncovalent interactions.The nanocomposites were characterized by NMR,FTIR,Raman,GPC,XRD and TGA measurements.The experimental results indicated that the chain extension of HTPB overcame the fragility and improved tenacity of thin films.SEM and TEM observations showed that segregated networks of MWCNTs was formed due to the cladding of PS-b-HTPB2-b-PS,presenting a parallel-arrangement topology of the MWCNTs in a continuous PS-b-HTPB2-b-PS phase;this improved the dispersibility of MWCNTs.Explored the content of MWCNTs and the chain length of PS toward the influence of vapor response.The nanocomposites were fabricated into vapor sensing elements for monitoring and preventing the leakage and diffusion of VOCs,which exhibited excellent responsive sensitivity,reproducibility and a low limit of detection(LOD)of 1 ppm when exposed to CH2CI2 vapor.The responsivity could be optimized by adjusting the content of MWCNTs and the length of PS chains.