| The overall objectives of this thesis are (i) to synthesize and characterize a fluorescent polymer having the rigid pentiptycene and bulky cholesteryl ester groups, (ii) to characterize and compare the sensing properties of fluorescent polymers using standard lab fluorimeter and optic-fiber probe, and (iii) to study the effect of film thickness and compositions on the sensing properties.The fluorescence quenching properties of polymer P1 thin films in response to vapor of 2,4-dinitrotulene (DNT) have been investigated by varying the film thickness, applying a undercoating of (3-aminopropyl)triethoxysilane (APTES) and blending with another polar polymer. A significant change in fluorescence intensity (51 % in 60-s) in response to DNT vapor exposure at ambient temperature was achieved when the polymer film coated on glass plate was about 2 nm in thickness. In comparison with the film of polymer alone, the film undercoated with 5-20 nm thick APTES and the film of polymer blend showed additional 18.5 % (in 20-s exposure) and 18.7 % (in 5-min exposure) decrease in fluorescence intensity, respectively. The use of polymer or polymer blend coated on optic-fiber tip for detection of DNT vapor has also been demonstrated. In comparison, an analogue polymer (P2) shows a larger fluorescence quenching percentage and faster response for a given time.Polymers P1 and P2 showed rapid fluorescence quenching response upon exposure to isocyanate vapor at ambient temperature, especially for aromatic isocyanates of industrial importance such as PPDI, TDI and NDI. Considering the synthesis and sensing performance, polymer P2 is the better candidate for isocyanate sensingA new conjugated polymer (P1) containing both the rigid pentiptycene and bulky cholesteryl ester groups was designed and successfully synthesized using the Sonogashira cross-coupling reaction. The monomers and the polymer were fully characterized by NMR and IR spectroscopy. Polymer P1 had the weight-average molecular weight of 100,000 relative to polystyrene standard, inherent viscosity of 0.92 dL/g at 30 °C and the onset temperature of 288 °C for 5 % weight loss in nitrogen. The thin film of P1 emits blue color with the maximum wavelength at 479 nm and the quantum yield of 0.30. |
