Poly ladder-type

Figure 9-1. Materials overview a few sclcclcd conjugated polymers and Ihcir properties have been compiled and ihe following abbreviations arc used DO-PPP...Poly(2-decyloxy-l,4-phcnylcnc), EHO-PPP...Poly(2-(2 -elhylliexyloxy)-l,4-phcnylenc), CN-PPP... Poly(2-(6 -cyano-6 -incthyl-licplyloxy)-l,4-phcnylene), m-LPPP... methyl-substituted ladder-type Poly( 1,4-phenylcne), and PLQY=phololuinincs-ecncc quanluni yield.

Figure 10-6. Chemical structure of the ladder-type poly(/xi/u-pheny-Icne). X represents u methyl-group and R and R are /i-hcxyl aud 1,4-dccylphcnyl, respectively.

S. Tasch, A. Niko, G. Leising, U. Scherf, Highly efficient electroluminescence of new wide band gap ladder-type poly(para-phenylenes), AppL Phys. Lett. 1996, 68, 1090. 

W. Graupner, G. Ccrullo, M. Lanzatti, M. Nisoli, E.J. W. List, G. Leising, S. De Silvcstri, Direct observation of ultrafast field-induced charge generation in ladder-type poly(para-phenylene). Phys. Rev. Lett. 1998, 81. 3259. 

Ladder-Type Poly(para-phenylene-czs-vinylene)s.216... 

Ladder-Type Poly(pflra-phenylene-cis-vinylene)s... 

In 1993, Scherf and Chmil described the first synthesis of a ladder-type poly(pflra-phenylene-czs-vinylene) (116) [138]. On the one hand, ladder polymer 116 represents, a planar poly(phenylene) containing additional vinylene bridges on the other hand, it is a poly(phenylenevinylene) with aryl-aryl linkages in the polymeric main chain. The target macromolecules, as fully aromatic ladder polymers, are composed of all-carbon six-membered rings in the double-stranded main chain (an example of angularly annelated poly(acene)s). 

E.J.W. List, L. Holzer, S. Tasch, G. Leising, M. Catellani, and S. Luzzati, Efficient, single layer yellow light emitting diodes made of a blend of a ladder-type poly(p-phenylene) and polyalkylthio-phene, Opt. Mater., 12 311-314, 1999. 

L. Romaner, G. Heimel, H. Weisenhofer, P.S. de Freitas, U. Scherf, J.-L. Bredas, E. Zojer, and E.J.W. List, Ketonic defects in ladder-type poly(p-phenylene)s, Chem. Mater., 16 4667-4674, 2004. 

G. Leising, S. Tasch, F. Meghdadi, L. Athouel, G. Froyer, and U. Scherf, Blue electroluminescence with ladder-type poly(p-phenylene) and p-hexaphenyl, Synth. Met., 81 185-189, 1996. 

XH Yang, D Neher, U Scherf, SA Bagnich, and H Bassler, Polymer electrophorescent devices utilizing a ladder-type poly(para-phenylene) host, J. Appl. Phys., 93 4413 -419, 2003. 

It was straightforward to apply the TRMC technique to study on-chain charge transport to ladder-type poly-phenylene (LPPP) systems because covalent bridging between the phenylene rings planarizes the chain skeleton, eliminates ring torsions, and reduces static disorder. One can conjecture that in these systems intra-chain motion should be mostly limited by static disorder and chain ends. To confirm this... 

Prins P, Grozema FC, Schins JM, Savenije TJ, Patil S, Scherf U, Siebbeles LDA (2006) Effect of intermolecular disorder on the intrachain charge transport in ladder-type poly (p-phenylenes). Phys Rev B 73 045204... 

Fig. 17. Proposed polymerization of a bisbenzocyclobutene to give a ladder type poly(o-xylylene) polymer 30...

Polythiophene derivative Ladder-type poly(p-phenylene)... 

An electrophilic substitution reaction has been used for the key ladderforming step in the synthesis of soluble ladder-type poly(phenylene)s [51-53]. These aromatic polymers have a ribbon-like rigid, planar structure. They are of interest because of their optical and electronic properties [51,54,55]. The preparation of these polymers was accomplished by two basic steps. The first step was the construction of a substituted poly(p-phenylene) backbone. The ladder structure was obtained by a subsequent intramolecular electrophilic ring closure reaction. For example, the syn-... 

Figure 17 Synthesis of soluble ladder-type poly(phenylene)s by a two-step process Construction of the Poly(p-phenylene) backbone and intramolecular ring closure. (From Ref. 51.)...

Electrochemical (cyclovoltametric) investigations of the ladder-type poly-(para-phenylene) species 71 support the results of the chemical oxidation (doping) experiments both in solution and in the solid state (film). A reversible oxidation takes place and it is well-separated into two waves especially in the solid-state experiment. These are assigned to the formation of radical cationic (79) and dicationic species (80), respectively. The halfwave potential (E1/2) for the first oxidation wave lies between 0.75 V (solution experiment) and 0.95 V (solid state - film) - versus a standard calomel electrode SCE) [106]. Consequently, one has to search for an alternative synthetic process to generate the ladder-type poly(phenylenemethide)s 77 or polymers containing extended segments of the fully unsaturated structure desired. The oxidation of polymeric carbanions appeared suitable, but it proved necessary to work under conditions which completely exclude water and air. 

Products 82 are of low chemical stability and rapidly decompose (several minutes) in air decomposition is slower (several days) in the absence of water and oxygen. Thus, these investigations have defined general limitations for poly(arylenemethide) synthesis, set by their chemical instability. A structural analysis of a decomposed ladder-type poly(arylenemethide) 76 has clearly shown that the bridge (methide position) is the site of attack with formation of hydroxyl- or hydroperoxyl-groups [102]. 

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