The preparation and vapor-induced response of a conductive nanocomposite based on poly(methyl acrylic acid)/expanded graphite by in situ polymerization

摘要

A poly( methyl acrylic acid)/expanded graphite (PMAA/EG) conductive nanocomposite was prepared by means of in situ intercalation polymerization using expanded graphite (EG) as conductive fillers and acrylic acid (MAA) as a monomer. The electrical resistance response of the model material was investigated upon exposure to several solvent vapors. The crystalline, morphology and functional group changes on the graphite surface were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The experimental results showed that the electrical resistance increases as the model material is exposed to such solvent vapors as tetrahydrofuran (THF), N, N-dimethylformamide (DMF), chloroform and acetone. In particular, PMAA/EG intercalation composite film displays an optimal responsiveness to chloroform vapor, exhibiting a selective positive vapor coefficient effect ( PVC). Expanded graphite with more polar groups, micropores and large basal spacing is in favor of the diffusion and absorption in organic solvent vapors. Meanwhile graphite nanosheets with a large aspect ratio ( ratio of diameter to thickness) are more propitious to the formation of PMAA/EG composite conductive networks. The existence of an ionic bond between the graphite and the chloroform molecules, and a hydrogen bond between the PMAA and the chloroform molecules as well as the charge repulsion interaction are all responsible for improving the responsiveness of the PMAA/EG intercalation composite film to chloroform vapor.