Chemical modification-induced improvement in the electrical characteristics of radiation-functionalized polypropylene sheets

Abstract

The development of conducting or semiconducting polymers is a highly interesting area due to the urgent need for new materials that combine several unique properties to be applied in a great variety of electrochemical devices. Polypropylene sheets were functionalized by radiation-induced grafting of acrylonitrile to import reactive nitrile groups into the inert polymer sheets. To improve the electrical characteristics, such as electrical conductivity, of the radiation-grafted sheets, a conjugated structure was developed via the repetition of the two-step condensation polymerization of p-phenylenediamine and glyoxal using the grafted nitrile groups as starting point. The grafted and treated polypropylene sheets were characterized using Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). FTIR spectra confirmed the occurrence of the grafting as well as the treatment of the grafted cyanide groups with p-phenylenediamine and reaction with glyoxal. TGA traces showed an improvement in the thermal stability of the grafted sheets by grafting and a reduction of such stability by chemical treatment. The electrical characteristics of the grafted and treated sheets were evaluated and compared with those of untreated polypropylene. The effects of degree of grafting and conjugated chain length on the electrical characteristics of the grafted sheets were also investigated. The results showed that the development of a conjugated chemical structure in the polypropylene sheets increases the conductivity by about five orders of magnitude. The electrical conductivity of polypropylenewas significantly increased as a result of the chemical development of a conjugated double-bond chain structure in the radiation-functionalized form. © 2009 Society of Chemical Industry.