Polyquinoline

A number of thermally stable polymers have been synthesized, but in general the types of stmctures that impart thermal resistance also result in poor processing characteristics. Attempts to overcome this problem have largely been concentrated on the incorporation of flexible groups into the backbone or the attachment of stable pendent groups. Among the class of polymers claimed to be thermally stable only a few have achieved technological importance, some of which are polyamides, polyimides, polyquin oxalines, polyquinolines, and polybenzimidazoles. Of these, polyimides have been the most widely explored. 

Polyquinolines are some of the most versatile thermally stable polymers they were developed during the 1970s in response to increasing demand for high temperature resistant materials and are undergoing commercial development (Maxdem, Inc., San Dimas, California). Evidence of their stabiUty is... 

Synthesis and Properties. Polyquinolines are formed by the step-growth polymerization of o-aminophenyl (aryl) ketone monomers and ketone monomers with alpha hydrogens (mosdy acetophenone derivatives). Both AA—BB and AB-type polyquinolines are known as well as a number of copolymers. Polyquinolines have often been prepared by the Friedlander reaction (88), which involves either an acid- or a base-catalyzed condensation of an (9-amino aromatic aldehyde or ketone with a ketomethylene compound, producing quinoline. Surveys of monomers and their syntheses and properties have beenpubhshed (89—91). 

The wide variety of ketomethylene and amino ketone monomers that could be synthesized, and the abiUty of the quinoline-forming reaction to generate high molar mass polymers under relatively mild conditions, allow the synthesis of a series of polyquinolines with a wide stmctural variety. Thus polyquinolines with a range of chain stiffness from a semirigid chain to rod-like macromolecules have been synthesized. Polyquinolines are most often prepared by solution polymerization of bis(i9-amino aryl ketone) and bis (ketomethylene) monomers, where R = H or C H, in y -cresol with di-y -cresyl phosphate at 135—140°C for a period of 24—48 h (92). 

Polyquinolines have also been obtained by a post-polymerization thermal treatment of poly(enamino nitriles) (93). The resulting polymers show excellent thermal stabiUty, with initial weight losses occurring between 500 and 600°C in air (tga) under nitrogen, initial weight loss occurs at about 600°C and there is a 20% weight loss up to 800°C. 

Bearing in mind the semiconductive properties of PCSs one might expect that these substances, being p-type semiconductors in air, possess photosensitizing activity. We, indeed, have demonstrated40 that PCSs, such as poly(schiff base)s, salts of poly(propynoic acid), or polyquinoline, are active photosensitizers of... 

Other materials which appear to be suitable as active battery el trodes are polyazulene poly (A-vinylcarbazole) polyquinolines and, most recently, polyaniline (PANI) panI, in particular, is a promising material for the... 

H. Kruger, S. Janietz, D. Sainova, and A. Wedel, New organo-soluble conjugated polyquinolines, Macromol. Chem. Phys., 204 1607-1615, 2003. 

DuPont is an active player in OLED technology. Polymers used in devices as emitting materials are poly(p-phenylenevinylene), poly(arylenevinylene)s, poly(p-phenylene), poly(arylene)s, polyquinolines, and polyfluorenes. In some cases, an anionic surfactant such as lithium nonylphenoxy ether sulfate was added to the above-mentioned polymeric emitters... 

Polyquinolines (PQ) are obtained by the Friedlander reaction of a bis-o-aminoaromatic aldehyde (or ketone) with an aromatic hisketomethylene reactant [Concilio et al., 2001 Stille, 1981]. The quinoline ring is formed hy a combination of an aldol condensation and imine formation (Eq. 2-221). Polymerization is carried out at 135°C in m-cresol with poly (phosphoric acid) as the catalyst. The reaction also proceeds under base catalysis, but there... 

In an effort to increase the processibility of polyquinolines, fluoromethylene groups have been successfully incorporated into the chain in place of Ar in the bis (ketomethylene) moiety (94). In fact, a small percentage of perfluorobutylene groups in the polyquinoline chain was sufficient to decrease the T significandy while still retaining other desired mechanical and thermal properties. Another approach was to prepare a series of oligomeric polyquinolines containing pendent biphenylenes and capped with either phenyl or biphenylene moieties (95). A representative list of different polyquinoline backbones and their properties appears in Table 3. 

All the flexible polyquinolines are readily soluble in chlorinated hydrocarbons such as methylene chloride and chloroform. Semirigid polyquinolines are soluble in tetrachloroethane or / /-cresol, but rigid polyquinolines are soluble only in strong acids like sulfuric and trifluoromethane sulfonic acid. Dilute solution properties of polyquinolines have been investigated by techniques such as membrane osmometry, light scattering, viscometry, and gel-permeation chromatography (96,97). 

Applications. Most of the stilbene-based polyquinolines display photoresponsive (98) and photomechanical effects as manifested by a contraction in polymer film samples upon irradiation. 

Polyquinolines have been used as polymer supports for transition-metal catalyzed reactions. The coordinating ability of polyquinoline ligands for specific transition metals has allowed their use as catalysts in hydroformylation reactions (99) and for the electrochemical oxidation of primary alcohols... 

Polyquinolines are good electrical insulators as indicated by conductivity values in the order of 10 15 —10 12 S/cm (101). However, by virtue of their extended conjugation, doped, wholly aromatic polyquinolines offer potential for high conductivity. Rigid polyquinolines display highest values of conductivity, generally on the order of 8—11 S/cm. 

Some biphenylene end-capped polyquinolines have been used to make carbon-fiber reinforced composites (102). However, properties of these composites dropped off significantly when oxidatively aged for 50—100 h at 316°C. 

Jen AKY, Ma H, Wu J, Wu X, Liu S, Dalton LR, Marder SR (2000) High performance side-chain aromatic polyquinolines for E-O devices. In Organic thin films for photonic applications. Optical Society of America, Washington DC, p 3... 

Neckers et al. [16, 17, 18] demonstrated that polyureas with backbone azobenzene groups (70) also underwent a photoviscosity effect when ultraviolet-irradiated. Stille et al. [19] reported that the intrinsic viscosity of polyquinoline (II) with backbone stilbene groups in di-m-cresyl phosphate/m-cresol decreased as much as 24% under ultraviolet light. The decrease was ascribed to the tram to cis isomerization of the stilbene groups. Because of its simplicity the mechanism (3) has been widely applied to other polycondensation or polyaddition polymers. 

A similar but more active chromophore 3 (RT-9800) was also incorporated as guest in a rigid-rod, high-temperature polyquinoline (PQ-100) (Scheme 1) [32]. Poling results from the guest-host polyquinoline thin films showed both exceptionally large electro-optic activity and long-term stability at 85 °C. After an initial drop from 45 to 26 pm in the first 100 hours, the electron-optic coefficient remained at 26 pm for more than 2000 hours (Fig. 3). 

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