Ladder poly

The emission from PIFs is still violet-blue, rather than a pure blue, and so to obtain a purer blue emission colour, a poly(ladder-type tetrapheny-lene) 99 has been made (Scheme 44) [119]. This polymer emits blue PL... 

Scheme 44 Synthesis of poly(ladder-type tetraphenylene)s...

PFs, PlFs, and poly(ladder-type pentaphenylene)s have methine bridges, and so are structurally related to LPPP 3. Stepladder polymers have also been prepared with other types of bridges. 

Light-Induced Electron Spin Resonance laddered poly(p ra-phenylene) lowest unoccupied molecular orbital molecular beam epitaxy... 

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.

Concerning the nature of electronic traps for this class of ladder polymers, we would like to recall the experimental facts. On comparing the results of LPPP to those of poly(para-phenylene vinylene) (PPV) [38] it must be noted that the appearance of the maximum current at 167 K, for heating rates between 0.06 K/s and 0.25 K/s, can be attributed to monomolecular kinetics with non-retrapping traps [26]. In PPV the density of trap states is evaluated on the basis of a multiple trapping model [38], leading to a trap density which is comparable to the density of monomer units and very low mobilities of 10-8 cm2 V-1 s l. These values for PPV have to be compared to trap densities of 0.0002 and 0.00003 traps per monomer unit in the LPPP. As a consequence of the low trap densities, high mobility values of 0.1 cm2 V-1 s-1 for the LPPPs are obtained [39]. 

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. 

In Figure 8-1 we show the chemical structure of m-LPPP. The increase in conjugation and the reduction of geometrical defects was the main motivation to incorporate a poly(/ -phenylene)(PPP) backbone into a ladder polymer structure [21]. Due to the side groups attached to the PPP main chain excellent solubility in nonpolar solvents is achieved. This is the prerequisite for producing polymer films of high optical quality. A detailed presentation of the synthesis, sample preparation,... 

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. 

Kjrushin Soichiro and Matsumoto Hideyuki, Ladder Poly silanes. 

Ladder-Type Oligo- and Poly(para-phenylene)s.177... 

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). 

Before the explanation of ladder poly silanes is started, ladder compounds of other Group 14 elements are briefly mentioned. Hydrocarbons with a ladder-shaped carbon framework are known as ladderanes. The study on ladderanes goes back to 1927, when bicyclo[2.2.0]hexane ([2]ladderane) was synthesized by the reduction of dy-l,4-dibromocyclohexane with sodium.19 Ladderanes so far reported are tricyclo[4.2.0.02,5]octane ([3]ladderane),20 tetracyclo[4.4.0.02,507,1°]decane21 ([4]ladderane), and a number of their derivatives (Fig. 3). 

Fig. 10. Lowest transition energies for ladder and linear polysilanes. Values for linear poly silanes are cited from reference 44.

The radical anions 1, anti-2, anti,anti-3, and anti,anti,anti-4 were generated by the reduction of the corresponding ladder polysilanes with potassium (Scheme 8). When the ladder poly silanes were treated with potassium in tetrahydrofuran (THF) at ca. — 70 °C, the solutions were immediately colored 1, purple anti-2, brown anti,anti-3, blue and anti,anti,anti-4, black. In the UV-visible-NIR spectra, several absorption bands appeared (Fig. 15). The intense absorption of anti,anti-3 and anti,anti,anti-4 in the near-infrared region is noted because it has been... 

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