Synthesis, characterization of PVC-graft-calixarene molecules and investigation of interactions of saw transducers with volatile organic compounds

In this thesis study, influence of surface coatings of PVC grafted t-butylcalix[6]arene on the sensitivity of surface acoustic wave sensors were investigated. For this purpose, PVC grafted p-tert-butylcalix[6]arene were chemically synthesized through the copper catalyzed azide-alkyne cycloaddition reactions. At the beginning of synthesis stage, PVC was functionalized by substitution reaction of chloride with azide groups and chemical structure was revealed by FTIR spectrometry. On the other side, p-tert-butylcalix[6]arene was alkylated with propargyl bromide using K2CO3 and characterizations which include NMR and FTIR have been carried out. Finally, these separately synthesized materials were reacted through the copper catalyzed azide-alkyne cycloaddition reactions. Chemical structure of PVC grafted t-butyl-calix[6]arene was characterized by using NMR and FTIR spectrometer. Coating solution was prepared by dissolving the synthesized material in DMF and it was coated on ST-cut SAW devices by electrospray coating technique. In order to observe effect of the coating thickness on sensor responses, three different SAW sensors which have different coating thickness were obtained by changing exposure time of solution. An experimental system has been designed to be used in this project in which examines the ability of the PVC-modified calixarenes to retain volatile organic compounds in nanogram concentrations. Sensitivity of the SAW sensors to volatile organic compounds was measured in this computer controlled gas flow and mixture system. Sensing properties of PVC grafted thin films were studied towards volatile organic compounds which were include acetone, ethanol, hexane, heptane, chloroform, toluene. Variation of the responses of the SAW sensors was investigated according to the coating layer thickness and interaction parameters between sensing layer and gas analyte. The influence of interaction of various functional groups with calixarene molecule to sensitivity has been analyzed, as well. In conclusion, it is aimed to study the effects of coated layers on the SAW transducer surface and the sensor properties of the SAW transducer. Therefore sensitivity, repeatability and detection performance of SAW sensors were measured by exposing of PVC grafted thin films towards VOC at variable concentration ratios.