FUNCTIONAL POLYMERS AND SUPRAMOLECULAR COMPOUNDS FOR CHEMICAL SENSORS

We present experimental data and theoretical concepts for the use of functional polymers and supramolecular compounds as layer materials of chemical sensors with high selectivities to monitor organic solvent molecules in air. Polysiloxanes and calixarenes, in particular, serve as model substances in this study. The bulk dissolution of solvent molecules into the polysiloxane layers leads to characteristic sensor signals of quartz microbalance, thermopile and interdigital capacitor transducers. Selectivities can be understood from a simple thermodynamic approach which correlates the partition coefficients of the solvents with the Gibbs enthalpy of dissolution. Surface effects of sensor signals from quartz microbalance transducers which have been coated with calixarene layers are studied as a function of temperature, partial pressure and thickness. Comparative results obtained from thermodesorption spectroscopy and force-field calculations show that specific key-lock interactions occur between calixarenes and solvent molecules.