The Use of Polyurethane Composites with Sensing Polymers as New Coating Materials for Surface Acoustic Wave-Based Chemical Sensors—Part II: Polyurethane Composites with Polylaurylmetacrylate, Polyisobutene, and Poly(chlorotrifluoroethylene-co-vinylidene Fluoride): Coating Results, Relative Sensor Responses and Adhesion Analysis

Abstract

This work presents the application of the methodology for the sensitization of surface acoustic wave-based sensors (SAW), developed in the first part of this work. The strategy of the method is the obtention of sensing layers with tailored chemical environments by taking advantage of the wide variety of chemical composition of the organic polymers, which have been used as sensing polymers, and combining them with polyurethane (PU) to form polymeric composites that show enhanced properties as sensing materials for the SAW sensor technology. In the first part of this work, the ultrasonic and adhesion characterization was correlated to the sensor responses of PU-polybutylmethacrylate (PBMA) composites of different relative concentrations of the sensing polymer (PBMA) and PU. The resulting coating layers obtained with the PU polymer composites improved the chemical and mechanical properties of the sensing layer without interfering with the quality of their sensor responses in comparison to those with the pristine polymer as the sensing material. In this second part of this work, three new polyurethane polymeric composites were analyzed. The new sensing materials were produced using polylaurylmetacrylate (PLMA), polyisobutene (PIB), and poly(chlorotrifluoroethylene-co-vinylidene fluoride) (PCTFE) as the sensing polymers combined with PU. The results of the new PU polymer composites showed consequently different properties depending on the type of sensing polymer used, reproducing, however, the previous features achieved with PU and polybutylmetacrylate (PBMA) composites, like the improvements in the adhesion and the resistance against an organic solvent and preserving, in each case, the sensor response characteristic of each sensing polymer used, as was also observed for the PU-PBMA polymeric composites. The results obtained with the new sensing materials validated the strategy and confirmed its generalization as a very suitable methodology for the sensitization of SAW sensors, strongly indicating the applicability and reliability of the method, which makes possible the choice of virtually any chemical environments for the sensitization of SAW sensor systems.