Electrical and IR spectroscopic studies of peroxopolytungstic acid/organic-inorganic hybrid gels

We investigated the electrical and structural properties of an organic-inorganic hybrid (ICS-PPG), composed of 3-isocyanatopropyl-triethoxysilane (ICS) and poly(propylene glycol)bis-(2-amino-propyl ether) (2-APPG), mixed with peroxopolytungstic acid (W-PTA), (W-PTA/ICS-PPG for short). Impedance spectroscopic measurements done on ICS-PPG gels hydrolysed with 4 mol.% HCl revealed that proton conductivity is about 10(-5) S/cm and increases two times when temperature is increased from room temperature to 80 degrees C. ICS-PPG with the added W-PTA exhibits room temperature proton conductivities from 1.86 x 10(-6) S/cm (10 mol.% W-PTA) to 1.45 x 10(-3) S/cm (99.18 mol.% W-PTA) while the proton conductivity of W-PTA gels is 2.54 x 10(-3) S/cm, All samples are characterised with low electronic conductivity (similar to 10(-8)-10(-9) S/cm). Results revealed that the addition of ICS-PPG to W-PTA increases thermal stability of the composites ( < 80 degrees C). IR vibrational band shifts and the narrowness of the bands observed in IR spectra of the composites suggest that W-PTA is homogeneously dispersed in the ICS-PPG network acid that only weak interactions exist between the W-PTA units in the composites. (C) 1999 Elsevier Science B.V. All rights reserved.