| Summary: | 博士 === 國立交通大學 === 應用化學系 === 92 === The goal of this research is to study the synthesis and optical properties of aromatic conjugated polyazomethines and poly(p-phenylene vinylene) related homopolymers and copolymers, as well as their application in chemosensors. In chapter one, a series of eight soluble conjugated aromatic polyazomethines containing p-phenylene, m-phenylene, m-terphenylene, 1,2,4-terphenylene and bicarbazylene - linkages in the backbone and various side-group substitutions have been synthesized by solution polycondensation of related aromatic diamines with armotic dialdehydes. These polyazomethines have been characterized and studied to understand the effects of the structure and the photoelectrical property relationship. In chapter two, six alkykthio group containing soluble homopolymers and copolymers of poly(phenylene vinylene) in meta- and para-linkages were synthesized by the Gilch, Witting, Knoevenagel and condensation polymerization. The conjugation lengths of the polymers were adjusted by substitutents and kink linkages. Thus, the photoluminescence spectra of the polymers can be tuned by the kink linkage and substitutent effects, emitting green to orange-red light. In chapter three , cyano substitution at α- and β-positions of light emitting monomers, i.e., 2,5-Bis( 2-thienyl-1-cyanovinyl -1-( 2’-ethylhexyloxy ) -4-methoxybenzene (α-TPT) and 2,5-Bis( 2-thienyl-2-cyanovinyl )-1-( 2’-ethylhexyloxy )-4-methoxybenzene (β-TPT), were synthesized by the Knoevenagel condensation reaction. Two corresponding polymers based onα-TPT andβ-TPT, i.e., poly[2,5-Bis(2-thienyl-1-cyanovinyl)-1- (2’-ethylhexyloxy)-4-methoxybenzene] (P1) and poly[2,5-Bis( 2-thienyl-2-cyanovinyl )-1-( 2’-ethylhexyloxy )-4-methoxy-benzene] ( P2 ) were obtained through FeCl3-oxidative polymerization. Theoretical calculations of the semi-empirical AM-1 level were carried out on model compounds (α-TPT and β-TPT), and the calculated torsion angles are in agreement with the electronic spectra data. The structures and the optical properties of the monomers and polymers were characterized by the FTIR, 1H-NMR, Mass, UV-Vis, and photoluminescence (PL). The thienyl-cyanovinylene-phenylene copolymers (P1and P2) containing high affinity thiophene unit and cyano substituted derivatives in the main chain lower the HOMO-LUMO gap and lead to bathochromic shift in the luminescence emission. Concentration quenching was observed in solid polymer films. Photoluminescence efficiency is strongly enhanced whenα-TPT and β-TPT are blended in a host polymer matrix like poly(N-vinyl carbozole) (PVK) or poly(methyl metacrylate) (PMMA). In addition, the PL intensities for polymer films ( P1 and P2 ) were weaker than the polymer blends; while the PL maximum peak wavelength for polymer films (P1 and P2 ) was red-shifted when compared with the polymer blends.
In chapter four, three prototypical light emitting conjugated polymers, two poly(p-phenylene vinylenes) (MEH-PPV and DP10-PPV) and a poly(diphenylaceylene), were examined for chemosensor applications to detect explosive compounds such as 2,4,6-trinitrotolene (TNT) and 2,4- and 2,6-dinitrotoluene (DNT). All polymer thin films showed high fluorescence quenching sensitivity towards TNT and DNT, indicating that a wide range of emissive conjugated polymers are potentially useful chemosensor materials for detecting landmines. The relative sensitivity of fluorescence quenching of the polymers has been rationalized in terms of the vapor pressure of the analytes, the solubility parameters of the polymers and the analytes, and the relative energy levels of the polymers.
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