Poly para-phenylene PPP

In many other cases polymers also contain benzene units as part of the chain structure (sections 2.3, 2.4 and 2.7). Poly-para-phenylene (PPP) 16 is the classical case of a conjugated polymer and of a rigid-rod species whose chain stiffness plays an important role in controlling supramolecular architecture (see... 

The story of poly-para-phenylene (PPP) synthesis again highlights the dilemma between experimentally simple approaches toward poorly-defined materials, albeit, with often attractive properties, such as mechanical strength and chemical... 

Phenylene-based polymers are one of the most important classes of conjugated polymers, and have been the subject of extensive research, in particular as the active materials in light-emitting diodes (LEDs) [1,2] and polymer lasers [3]. These materials have been of particular interest as potential blue emitters in such devices [4], The discovery of stable blue-light emitting materials is a major goal of research into luminescent polymers [5]. Poly(para-phenylene) (PPP, Scheme 1, 1) is a blue emitter [6], but it is insoluble and so films of PPP have to be prepared via precursor routes [7]. Substitution with long alkyl... 

Poly(para-phenylene) (PPP, 64) is insoluble and infusible and so films of PPP must be made by precursor routes (Scheme 6.19) [105]. The first of these, which was developed at ICI [106, 107], utilizes a radical polymerization of the diacetate 82 to produce a precursor polymer 83 that is thermally converted to PPP. This method produces PPP containing about 15% 1,2-linkages. A totally para-polymer can be made by the method of Grubbs involving the stereoregular nickel-catalyzed living polymerization of the bis(silyl ether) 84 to 85, and then its conversion to 83 [108-110],... 

Unsubstituted poly(para-phenylene) PPP 1 as parent system of the substance class is an insoluble and infusible material, available by a variety of synthetic methods [10,11]. The lack of solubility and fusibility hinder both unequivocal characterization and the processing of PPP. In addition, PPP 1 appears as an ill-defined material possessing a considerable number of structural defects (branching, 1,2-coupling). Entries to the preparation of structurally defined, processable PPPs have evolved based on numerous synthetic principles. 

Benzene c -diols, namely, cw-3,5-cyclohexadien-l,2-diols abbreviated as DHCD, can be used for synthesis of poly(para-phenylene) (PPP), which is a material with high thermal stability and electricity conducting ability when doped. Several types of bacterial dioxygenases, that can catalyze the conversion of aromatic componnds to their corresponding c -diols, which can be polymerized to form PPP, are discnssed. 

It has been shown [80] that organic semiconductors with the lowest redox potentials (which reflect the ionization potentials) of —0.2 V and 0.2 V vs SSCE for PPy and PANI, respectively, interact reversibly with ammonia. However, other polymers, such as PT (0.7 V), PA (0.7 V) and poly(para-phenylene) (PPP) (1.6 V) [81], all have higher redox potentials and their interaction is reported to be irreversible. The reversible changes of the transitions in the optical spectra correspond to the doping/undoping process. The results obtained on PT films, upon exposure to NO2, SO2 [82], or on PPy films during their exposure to NH3 [83], or on PPy and PPP films... 

A weak peak (labelled II or b), predominantly polarized along the short-axis in poly(para-phenylene) (PPP), but along the long-axis in PPV. This feature becomes more pronounced when there is chemical substitution, as in the case of MEH-PPV illustrated in Fig. 11.1(a). 

Section 3 then reviews the behavior of diblock copolymers in mixed micelles with surfactants. Section 4 discusses other polymer surfactant mixtures, such as mixtures of amphiphilic poly(para-phenylenes) (PPP) with nonionic surfactants [48]. The packing parameter and the curvature of an amphiphilic BCP are not only influenced by means of co-micellization with a surfactant. Both parameters can also be influenced by changing the solvent quality for one of the blocks, e.g., by adding alcohol or salt. Denkova et al. have shown that this also leads to structural changes [49], However, despite the similarity of both approaches, the present review will only focus on aqueous BCP surfactant mixtures. Surfactants can also be used to assist structure formation in BCP thin films [50], This is an area of growing importance, but is beyond the scope of the present contribution. 

Figure 26 Frechet-type monodendrons (generations 1, 2, and 3) possessing various reactive groups at the focal point. Rod-shaped, dendritic-linear architectural copolymers obtained by coupling respective dendrons to linear poly(para-phenylene) (PPP) backbone. (Courtesy J. Am. Chem. Soc. 119 3297, 1997. Copyright 1997 American Chemical Society.)...

The synthetic routes to polyarylenes make use of the efficient aryl-aryl bond forming reactions that have been developed over the last century. These come in three categories oxidative coupling, reductive coupling, and transition-metal-mediated organometallic cross-coupling reactions (Scheme 6). Of these oxidative coupling, which is here represented by the Kovacic route to poly(para-phenylene) (PPP), is... 

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