Sensory materials

There have been a number of different synthetic approaches to substituted PTV derivatives proposed in the last decade. Almost all focus on the aromatic ring as the site for substitution. Some effort has been made to apply the traditional base-catalyzed dehydrohalogenation route to PTV and its substituted analogs. The methodology, however, is not as successful for PTV as it is for PPV and its derivatives because of the great tendency for the poly(u-chloro thiophene) precursor spontaneously to eliminate at room temperature. Swager and co-workers attempted this route to synthesize a PTV derivative substituted with a crown ether with potential applications as a sensory material (Scheme 1-26) [123]. The synthesis employs a Fager condensation [124] in its initial step to yield diol 78. Treatment with a ditosylate yields a crown ether-functionalized thiophene diester 79. This may be elaborated to dichloride 81, but pure material could not be isolated and the dichloride monomer had to be polymerized in situ. The polymer isolated... 

The dominant attribute that has driven interest in fluorescent conjugated polymers (CPs) sensory materials is their ability to produce signal gain in response to interactions with analytes. The increased sensitivity (amplification) is derived from the ability of a conjugated polymer to serve as a highly efficient transport medium of electronic excitation. Analyte specificity in CP-based sensors results from the covalent or physical integration of receptors, imprinting, and/or the CP s overall electrostatic and chemical characteristics. The observed amplification is a... 

Yang J-S, Swager TM (1998) Porous shape persistent fluorescent polymer films an approach to TNT sensory materials. J Am Chem Soc 120 5321-5322... 

Wang B, Wasielewski MR (1997) Design and synthesis of metal ion-recognition-induced conjugated polymers an approach to metal ion sensory materials. J Am Chem Soc 119 12-21... 

This relationship also conveys one of the reasons why the sensing of explosives can be so effective with this method. Most explosives, especially TNT and other nitroaromatic compounds, are highly electron deficient and have favorable reduction potentials. For instance, the reduction potential of TNT and DNT are only —0.7 and—1.0 V (versus SCE) respectively, quite favorable when compared with other electron acceptors, such as 1,4-dicyanobenzene (—1.7 V versus SCE). This means that if the sensory material emits hght, for example, at 460 nm, the oxidation... 

Another interesting application of Jt-conjugated systems is their use as chemosensors. For example, a modified dithienophosphole oxide 160 (see Scheme 49 for the synthesis of its precursor) that incorporates boryl-end caps is a very sensitive and selective sensory material for the fluoride ion (Scheme 126). Treatment of this derivative by fluoride induces a red shift of the emission maximum (160, 452 nm 373, 485 nm) that is visible to the naked eye. This shift in the fluorescence emission can even be detected down to micromolar concentrations of fluoride ion notably, the addition of other halides (CP, Br, P) does not affect the fluorescence in any way <20060L495>. 

As a result of their low vapour pressures, explosives detection in realtime using sniffer technologies presents significant detection challenges. A breakthrough that has enabled a paradigm shift toward explosive vapour detection came in 1998 when our group developed a sensory material with extraordinary sensitivity to TNT and DNT (trinitrotoluene and di-... 

T.M. Swager, Conjugated polymer sensory materials, Chem. Rev. 100 (2000) 2537-2574. 

E. Towers and V. Williams, Using novel fluorescent polymers as sensory materials for above-ground sensing of chemical signature compounds emanating from buried landmines, IEEE Trans, on Geoscience and Remote Sensing, 39 (2001) 1119-1128. 

POLYDIACm LENE-CONTAINING LIPOSOMES AS SENSORY MATERIALS... 

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