Films of the conjugated polydiacetylenes (PDAs) can function as chromatic temperature, chemical and stress sensors, and can be prepared by spin-coating from monomer solutions followed by polymerization using UV-or γ-irradiation. PDAs thus have the potential for advanced applications as sensors Nanocomposite ZnO: PDA and ZnO/ZrO2: PDA thin films have been prepared and their structural properties have been characterized by a variety of techniques including Fourier transform infrared spectroscopy, Raman spectroscopy, differential thermal calorimetry (DSC) and extended x-ray absorption fine structure (EXAFS) measurements. We have conducted testing and calibration of the thermal and stress sensing properties of the composite films using optical density measurements. It was also observed that the fluorescent red phase transforms to a non-flourescent blue phase in the presence of trace amounts of chemical vapors. Results on the sensing of trace amounts of vapors of tri-nitrotoluene (TNT) and dinitrotoluene (DNT) by optical densitometry and fluorescence, and efforts to enhance the chemical sensitivity of TNT detection by addition of single wall carbon nanotubes to the polydiacetylene (PDA), will also be discussed.