Polythiophene emission

A similar approach for detecting the presence of specific proteins has also been reported by Nilsson and coworkers [26]. In this study, a complex between a calmodulin, a small calcium-binding protein, and the zwitter-ionic polythiophene POWT was used to detect the presence of calcineurin. The interaction between the POWT-camodulin complex and calcineurin changed the emission profile from POWT, and no observable changes were observed upon exposure of the complex human serum albumin, suggesting that the complex could be used for the specific detection of calcineurin. 

Fig. 17 (a) Chemical structure of polythiophene poly((3,3"-di[(S)-5-amino-5-carbonyl-3-oxapen-tyl]-[2,2 5 2"])-5-,5"-terthiophenylene hydrochloride), PONT, (b) Emission spectra of 6.5 pM PONT—HC1 (on a chain basis) in 25 mM HC1 (black spectrum), 25 mM HC1 with 5.0 pM of native bovine insulin (blue spectrum), 25 mM HC1 with 5.0 pM fibrillar bovine insulin (red spectrum). The emission spectra were recorded with excitation at 400 nm [31]... 

The inclusion of 5 wt% PCBM [l-(3-methoxycarbonyl)propyl-l-phe-nyl-[6,6]C6i] in the spin-coating solutions resulted in efficient polymer emission quenching for all the polythiophenes studied. The transient absorption spectra of the amorphous poly(541)/PCBM blend film. At 10 ps exhibited an absorption peak around 700 nm, similar to that observed for the poly(541) pristine film. The shape of the transient spectrum varied with time, with the absorption peak shifting from 700 nm at 10 is to 900 nm for time delays >100 (is, demonstrating the formation of two distinct transient species in the blend film. The monoexponential lifetime was t = 8 (is under Ar atmosphere and significantly shortened under 02 atmosphere. Monoexponential phase is therefore assigned to the decay of poly(541) triplet excitons. 

A second major class of emissive polymer is based on polythiophene [8], Again, substitution in this case at the -3- position of the thiophene ring is used to solubilize the polymer and to time the emission wavelength [9]. Other heterocyclic conjugated polymers are represented by polypyridine [10] and polypyridi-nevinylene [11]. Since each of these contains electron-deficient aromatic groups, they lend to be better electron transporters than their phenylene analogs. They emit primarily in the blue. 

The chiral polythiophene, poly(3- (.S )-5-amino-5-carboxyl-3-oxapcntyl -2,5-thiophenylene) hydrochloride, l-POWT, ring-functionalized with the amino acid L-serine, has been synthesized by Inganas and coworkers,69,168 and was found to exhibit pH-dependent UV-visible, fluorescence emission, and CD spectra. At a pH equal to the isoelectric point of the amino acid, the poly thiophene chains separate and adopt a nonplanar right-handed helical conformation. Increasing the pH leads to a more planar conformation of the backbone and aggregation of the polymer chains. 

By 1995 one finds that the main actors are different polymers, a change which can be partly attributed to the recent interest in semiconductor properties, especially light emission. In the field of conduction, polyacetylene has given its place to polyaniline, a polymer with a fascinating rich chemistry and a promise of good processability. In the semiconductor arena, the most studied polymer of the past decade is polythiophene, or rather its soluble derivatives which lend themselves very well to various fabrication processes. Another polymer, one which was only mentioned briefly in the 1986 Handbook, is competing with polythiophene for application in semiconductor devices poly(pura-phenylene vinylene). These three polymers received very little interest before 1985 no crystallographic studies had been published at that time. 

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