Conjugation length poly

Fig. 2. A poly(phenylacetylene) dendrimer with an energy gradient across the conjugation length of the acetylene units from the periphery to the focal point...

The poly(cyclodiborazane)s containing the transition metals palladium and platinum in their backbone were prepared (scheme 26).39 These polymers exhibited an extension of ir-conjugation length via their transition metal and cyclodiborazane moieties. 

R. E. Martin, T. Mader, F. Diederich, Monodisperse Poly(triacetylene) Rods Synthesis of a 11.9 nm Long Molecular Wire and Direct Determination of the Effective Conjugation Length by UV/Vis and Raman Spectroscopies , Angew. Chem Int. Ed. Engl. 1999,38, 817-821. 

T. Ahn, M.S. Jang, H.-K. Shim, D.-H. Hwang, and T. Zyung, Blue electroluminescent polymers control of conjugation length by kink linkages and substituents in the poly(p-phenylene vinylene)-related copolymers, Macromolecules, 32 3279-3285, 1999. 

Y. Pang, J. Li, B. Hu, and F.E. Karasz, A highly luminescent poly[(m-phenylene vinylene)-a/t-(p-phenylene vinylene)] with defined conjugation length and improved solubility, Macromolecules, 32 3946-3950, 1999. 

F.-I. Wu, R. Dodda, D.S. Reddy, and C.-F. Shu, Synthesis and characterization of spiro-linked poly(terfluorene) a blue-emitting polymer with controlled conjugated length, J. Mater. Chem., 12 2893-2897, 2002. 

While the octamer 331 has Xmax = 458 nm, electrochemically generated poly(3-alkyl-a-thiophene)s have a noticeable smaller 7max value of 430-440 nm in solution. These data support the notion that the effective conjugation length in conjugated thiophene polymers may only be 6-7 monomer units long. 

The conjugation length of poly(3-alkylthiophene)s can be determined from the absorption maximum in the electronic spectrum. Whereas regioregular (i.e., head-tail) poy(3-octylthiophene) (POT) displays a maximum at 442 nm in CHCl3/Freon-113 solution, the absorbance maximum of 504 is blue shifted by 114 to 328 nm. This blue shift could arise from a particularly low molecular weight. 

The effect of molecular size, conjugation length, and competition with ex-cimer formation on ESIPT in conjugated polymers, in which the intramolecularly hydrogen-bonded moieties reside in the main domain, has been examined [204], The polymers were poly(5 -(2 -hydroxy)phenylenebenzobisoxazole (56) and poly(4 -(2 -hydroxy)phenylenebenzobisoxazole (57). A large extent of -rr-elec-tron delocalization is found to inhibit the ESIPT process. Excimer formation is found to be competitive with ESIPT in the polymers studied, whereas molecular size does not inhibit ESIPT. 

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