Measurements of elastic properties of polymeric humdity-sensitive films at different temperatures

Chemically sorbent polymeric films are commonly coated on acoustic wave devices to realize gas or vapor sensors. Temperature variations, as well as analyte adsorption, lead to softening of the film, producing a perturbation in the acoustic wave/film interaction. To achieve a high level of sensor's performance, the chemically sensitive coating has to be characterized in terms of acoustic parameters temperature and frequency dependence. An acoustic wave device has been used as a probe of the storage and loss moduli of a thin viscoelastic film over a range of temperature (20 °C-150 °C) and of frequency (factor of more than 20). Using an equivalent circuit model of the acoustic wave/thin viscoelastic film interaction, the overmentioned moduli have been deduced as a function of temperature from the experimental data for Poly(bis-tributhylphosphine-Ni-diethynylbiphenyl), Ni-DEBP, coated acoustic device, previously tested as a sensitive layer for relative humidity detection.