Oxygen conjugated polymers

In recent years further concepts have been developed for the construction of polymer-based diodes, requiring either two conjugated polymers (PA and poly(A-methyl-pyrrole) 2 > or poly(A-methylpyrrole in a p-type silicon wafer solid-state field-effect transistor By modifying the transistor switching, these electronic devices can also be employed as pH-sensitive chemical sensors or as hydrogen or oxygen sensors 221) in aqueous solutions. Recently a PPy alcohol sensor has also been reported 222). 

Although the exact mechanism of the fluorenone formation is not known, it is believed that the monoalkylated fluorene moieties, present as impurities in poly(dialkylfluorenes), are the sites most sensitive to oxidation. The deprotonation of rather acidic C(9)—H protons by residue on Ni(0) catalyst, routinely used in polymerization or by metal (e.g., calcium) cathode in LED devices form a very reactive anion, which can easily react with oxygen to form peroxides (Scheme 2.26) [293], The latter are unstable species and can decompose to give the fluorenone moiety. It should also be noted that the interaction of low work-function metals with films of conjugated polymers in PLED is a more complex phenomenon and the mechanisms of the quenching of PF luminescence by a calcium cathode was studied by Stoessel et al. [300],... 

Polyacetylene is very susceptible to attack by oxygen. The polymer loses its metallic lustre and becomes brittle when exposed to air. However, other conjugated polymers were found. Polypyrrole, polythiophene, polyaniline, polyphenylenevinylene (Figure 6.4), and others are conjugated polymers whose bonding and con-... 

Long-lived photoluminescence, at 826 nm, is reported (t 15 (is) for thin films of the processable, -conjugated polymer, poly(3-hexylthio-phene) (93JA8447). Excitation of the n—n transition with 518 nm light (So >S ) yields only very weak luminescence of 826-nm light, even at 18 K. The emission is enhanced, to point where it can be observed at room temperature, when the excitation wavelength is 250 nm, but it is completely quenched by oxygen. Prompt fluorescence decays within... 

The newest series of polymers based on a phosphorus-carbon backbone are poly(meth-ylenephosphines) of structure [-P(R)-CR2-] , produced by the polymerization of phospha-alkenes, P(R)=CR2.47a These polymers react with oxygen to form species of type [-P(R)(0)-CR2-] . A related polymer with phenyl rings in the backbone has also been described.47b This is a pi-conjugated polymer with P=C bonds in the main chain. 

Conjugated polymers are very susceptible to degradation when exposed to atmospheric gases, causing the conductivity to vary with time. Exposure of as-prepared conjugated polymers to oxygen can lead to an initial increase in... 

The electrical conductance of carbon nanotubes is sensitive to the chemical environment of the tubes. A large difference in the electrical conductance is observed for the carbon nanotubes in the presence of air and oxygen atmosphere. " " It is possible to tune the electrical conductance of carbon nantubes reversibly using adsorbent gas molecules. The carbon nanotubes were also used to increase the conductance of a conjugated polymer for the development of electroluminescence polymer-nanocomposites. " ... 

In Fig. 4 the after-pulse growth of the PR-TRMC transients due to positive ion scavenging by different Tt-bond conjugated polymers in oxygen saturated benzene is illustrated. From kinetic fits to the transients, using the known free-ion yield in benzene, the intrachain hole mobility could be determined and the values were found to vary from a low of 0.02 cm /Vs for the polythiophene to a high of 0.74 cm /Vs for the polyfluorene derivative. Mobility values in the... 

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