Relationships among Resonant Frequency Changes on a Coated Quartz Crystal Microbalance, Thickness Changes, and Resistance Responses of Polymer−Carbon Black Composite Chemiresistors

The relationships among frequency changes on a film-coated quartz crystal microbalance, thickness changes, and dc resistance changes have been investigated for carbon black−insulating polymer composite vapor detectors. Quartz crystal microbalance (QCM) measurements and ellipsometry measurements have been performed simultaneously on polymer films that do not contain carbon black filler to relate the QCM frequency change and the ellipsometrically determined thickness change to the analyte concentration in the vapor phase. In addition, quartz crystal microbalance measurements and dc resistance measurements on carbon black composites of these same polymers have been performed simultaneously to relate the QCM frequency change and dc electrical resistance response to the analyte concentration in the vapor phase. The data indicate that the dc resistance change is directly relatable to the thickness change of the polymers and that a variety of analytes that produce a given thickness change produce a constant resistance change for each member of the test set of polymers investigated in this work.