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Ladder-Type Polyphenylenes

Scherf and Mullen prepared (Scheme 47) the ladder-type polyphenylene (LPPP, 5) with methine bridges [126-129], via a poly(diacylphenylene-co-phenylene) precursor copolymer 103 obtained by an AA-BB type Suzuki polycondensation. The key step is the polymer analogous Friedel-Crafts ringclosing reaction on the polyalcohol 104, obtained by the reduction of 103. This was found to proceed quickly and smoothly upon addition of boron-trifluoride to a solution of 104 in dichloromethane. The reaction appeared to be complete by both NMR and MALDI-TOF analysis, indicating the presence of less than 1% of defects due to incomplete ring closure. LPPPs with num-... [Pg.35]

Scheme 52 Synthesis of a ladder-type polyphenylene with dihydroxyethane bridges... Scheme 52 Synthesis of a ladder-type polyphenylene with dihydroxyethane bridges...
Scheme 53 Synthesis of ladder-type polyphenylene with ethene bridges... Scheme 53 Synthesis of ladder-type polyphenylene with ethene bridges...
Scheme 54 Ladder-type polyphenylene by alkyne cydisation... Scheme 54 Ladder-type polyphenylene by alkyne cydisation...
Therefore, it was our idea to proceed from linear to ladder-type polyphenylene structures by bridging neighboring benzene rings via methylene groups. This would not only enforce a planarization of the whole t-system, but also provide extra carbons to attach solubilizing alkyl chains without compromising the conjugation. [Pg.65]

The synthesis of these ladder-type polyphenylenes 2 and 3, as first accomplished in our group by Ullrich Scherf [120, 121], was realized via suitably functionalized polyphenylene precursors 2a and 3a, which were then transformed into the target ribbon via a polymer-analogous Friedel-Crafts cyclization [122, 123] (Scheme 2). [Pg.66]

Scheme 2 Synthesis of ladder-type polyphenylenes using para- and meto-dibenzoyl benzene building blocks, and dehydrogenation of 3b to polymer 3 with para-quinodimethane repeat units. No control over the configuration at the bridging methylene carbons could be achieved... Scheme 2 Synthesis of ladder-type polyphenylenes using para- and meto-dibenzoyl benzene building blocks, and dehydrogenation of 3b to polymer 3 with para-quinodimethane repeat units. No control over the configuration at the bridging methylene carbons could be achieved...
Scheme 3 Ladder-type polyphenylene 5 with vinylene bridges, an early version of graphene nanoribbons... Scheme 3 Ladder-type polyphenylene 5 with vinylene bridges, an early version of graphene nanoribbons...
Measurements of thermally stimulated cirrrents in our ladder-type polyphenylenes probe the density of mobile charge carriers after detrapping and reveal extremely low trap densities [136,137]. [Pg.68]

Grimsdale, A. C. and MUllen, K.i Polyphenylene-type Emissive Materials Poly(para-phen)d-ene)s, Polyfiuorenes, and Ladder Polymers. Vol. 199, pp. 1-82. [Pg.240]

Polyphenylene-type Emissive Materials Poly(para-phenylene)s, Polyfluorenes, and Ladder Polymers... [Pg.298]

As already briefly mentioned, easily the most obvious change regarding optical properties appears in the transition from the open-chain precursor polymers to the planarized PPP ladder polymers (LPPP). The primary single-stranded coupling product (a benzoyl-substituted polyphenylene) from a Suzuki-type polycondensation between an alkyl- or alkoxy-substituted 2,5-dibromo-1,4-dibenzoylbenzene derivative and 2,5-dihexyl-l,4-phenylenediboronic acid is colorless with an absorption maximum Amax of 264 nm [n-TT transition c = 39,000 L/(moI cm)l (19]. This absorption behavior supports the strongly twisted structure of the main PPP chain. The mutual distortion of the aromatic subunits reduces the conjugative interaction to a minimum, so that the typical electronic properties of a conjugated polymer are almost completely lost. [Pg.367]

Fig. 29.14 Electroluminescence spectra for the ladder polyphenylene of the type shown in Fig. 29.4, with Ri = C6H4-C10H21, R2 = C6H13, and = H. The ladder polymer is diluted with polystyrene, so the weight fraction of the ladder polymer is (a) 30%. (b) 10%, and (c) 1%. Note that blend (a) shows yellow emission and blend (c) shows substantially blue emission. (From Ref. 66.)... Fig. 29.14 Electroluminescence spectra for the ladder polyphenylene of the type shown in Fig. 29.4, with Ri = C6H4-C10H21, R2 = C6H13, and = H. The ladder polymer is diluted with polystyrene, so the weight fraction of the ladder polymer is (a) 30%. (b) 10%, and (c) 1%. Note that blend (a) shows yellow emission and blend (c) shows substantially blue emission. (From Ref. 66.)...

See other pages where Ladder-Type Polyphenylenes is mentioned: [Pg.238]    [Pg.3]    [Pg.34]    [Pg.228]    [Pg.234]    [Pg.136]    [Pg.3]    [Pg.20]    [Pg.932]    [Pg.156]    [Pg.367]    [Pg.835]    [Pg.871]    [Pg.61]    [Pg.24]    [Pg.163]    [Pg.575]    [Pg.14]   
See also in sourсe #XX -- [ Pg.3 , Pg.34 ]




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