Conjugated polymers chromophores

C1.5.4.5 CONJUGATED POLYMERS, CHROMOPHORE AGGREGATES, AND MICROHETEROGENEOUS MATERIALS... 

An important challenge in the design of novel conjugated polymers is the synthesis of materials with tailor-made solid-state electronic properties. This section outlines the synthesis of the most significant classes of poly(para-phenylenevinylene)s (PPVs), poly(para-phenylene)s (PPPs), and related structures. Furthermore, this review demonstrates that the chromophoric and electronic properties of conjugated rr-systems are sensitive to their molecular and supra-molecular architecture. 

Schlindler F, Lupton JM, Feldmann J, Scherf U (2004) A universal picture of chromophores in 7i-conjugated polymers derived from single-molecule spectroscopy. Proc Natl Acad Sci 101 14695-147000... 

Gaylord BS, Heeger AJ, Bazan GC (2003) DNA hybridization detection with water-soluble conjugated polymers and chromophore-labeled single-stranded DNA. J Am Chem Soc 125 896-900... 

Pu KY, Pan SYH, Liu B (2008) Optimization of interactions between a cationic conjugated polymer and chromophore-labeled DNA for optical amplification of fluorescent sensors. J Phys Chem B 112 9295-9300... 

Ley and Schanze have also examined the luminescence properties of the polymers Pq, Pio> P25> and P50 in solution at 298 K, and in a 2-methyltetrahydro-furan solvent glass at 77 K. These spectroscopic studies reveal that fluorescence from the 71,71" exciton state is observed at Amax=443 nm, 2.80 eV in the polymers P0-P50 at 298 and 77 K, but the intensity and lifetime of the fluorescence is quenched as the mole fraction of Re in the polymers is increased. This indicates that the metal chromophore quenches the 71,71" state. The quenching is inefficient even when the mole fraction is large, suggesting that interchain diffusion of the 71,71" exciton is slow compared to its lifetime [70]. Phosphorescence from the 71,71" state of the conjugated polymer backbone is observed at > max=b43 nm, 1.93 eV in P10-P50 at 77 K, and emission at Amax=690 nm, 1.8 eV is assigned to the d7i(Re) 7i oiy MLCT transition. 

Color. All aromatic azopolymers are colored owing to the strongly chromophoric azogroup. Even the azoblock copolymer derived from a phenyl oxide-isophthalamide backbone (discussed earlier) which has only one azogroup per repeat unit of a molecular weight of 3500 is bright yellow. Naturally, the shade of color of individual polymers depends on the structure of the repeat unit as expected, fully conjugated polymers... 

Conjugated polymers (CP) are highly chromophoric systems, which makes Raman spectroscopy and in particular its resonance excitation version a very attractive tool to investigate vibronic properties and electronic structures. IR spectroscopy has been used mainly to study the doping process and structural phase transitions. 

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