Poly precursor routes

Poly(arylene vinylenes). The use of the soluble precursor route has been successful in the case of poly(arylene vinylenes), both those containing ben2enoid and heteroaromatic species as the aryl groups. The simplest member of this family is poly(p-phenylene vinylene) [26009-24-5] (PPV). High molecular weight PPV is prepared via a soluble precursor route (99—105). The method involves the synthesis of the bis-sulfonium salt from /)-dichloromethylbenzene, followed by a sodium hydroxide elimination polymerization reaction at 0°C to produce an aqueous solution of a polyelectrolyte precursor polymer (11). This polyelectrolyte is then processed into films, foams, and fibers, and converted to PPV thermally (eq. 8). 

The scope of Wessling route has been extended by Mullen and co-workers to develop a soluble precursor route to poly(anthrylene vinyiene)s (PAVs) [51]. It was anticipated that the energy differences between the quinoid and aromatic resonance structures would be diminished in PAV relative to PPV itself. An optical band gap of 2.12 eV was determined for 1,4-PAV 29, some 0.3 eV lower than the value observed in PPV. Interestingly, the 9, lO-b/.v-sulfonium salt does not polymerize, possibly due to stcric effects (Scheme 1-9). 

The strategy of Kaeriyama represents a so-called precursor route and was developed to overcome the characteristic shortcomings (insolubility, lack of process-ability) of previous PPP syntheses. The condensation reaction is carried out with solubilized monomers, leading to a soluble polymeric intermediate. In the final reaction step this intermediate is then converted, preferentially in the solid state allowing the formation of homogeneous PPP films or layers, into PPP (or other poly(arylene)s). 

The sulfonium precursor route may also be applied to alkoxy-substituted PPVs, but a dehydrohalogenation-condensation polymerization route, pioneered by Gilch, is favored 37]. The polymerization again proceeds via a quinomethide intermediate, but die syndicsis of the conjugated polymer requires only two steps and proceeds often in improved yields. The synthesis of the much-studied poly 2-methoxy-5-(2-ethylhexyloxy)-l,4-phenylene vinylene], MEH-PPV 15 is outlined in Scheme 1-5 33, 35]. The solubility of MEH-PPV is believed to be enhanced by the branched nature of its side-chain. 

Other poly(2,5-dialkoxy-1,4-phenylene vinylene)s have been prepared in a similar fashion [34, 35, 40, 41]. Alternatively, a soluble a-halo precursor polymer 17 may be obtained by using less than one equivalent of base (Scheme 1-6). This may then be converted into fully conjugated material 16 by thermal treatment. This halo-precursor route may be preferred if the fully conjugated material has limited solubility or if incomplete conversion is desired. 

V.P. Conticello, D.L. Gin, and R.H. Grubbs, Ring-opening metathesis polymerization of substituted bicyclo[2.2.2]octadienes a new precursor route to poly(p-phenylene vinylene), J. Am. Chem. Soc., 114 9708-9710, 1992. 

P.L. Burn, D.D.C. Bradley, R.H. Friend, D.A. Halliday, A.B. Holmes, R.W. Jackson, and A. Kraft, Precursor route chemistry and electronic properties of poly(p-phcnylcnc vinylene), poly[(2,5-dimethyl-p-phenylene)vinylene] and poly[(2,5-dimethoxy-p-phenylene)vinylene], J. Chem. Soc. Perkin Trans., 1 3225-3231, 1992. 

T. Ahn, S. Ko, J. Lee, and H. Shim, Novel cyclohexylsiyl — or phenylsiyl-substituted poly(p-phe-nylene vinylene)s via the halogen precursor route and Gilch polymerization, Macromolecules, 35 3495-3505, 2002. 

Thus, N-pyrimidine phthalimide reacted with hexylamine at room temperature to form an amide-amide. The initial amide-amide formation proceeded more rapidly in chloroform as compared to dimethylsulfoxide (DM SO). However, the ring closure reaction to the imide was favored by the more polar, aprotic DMSO solvent, yielding the imide in nearly quantitative yield after 3 hours at 75 °C. The authors were able to utilize this synthetic approach to prepare well-defined segmented poly(imide-siloxane) block copolymers. It appears that transimidi-zation reactions are a viable approach to preparing polyimides, given that the final polyimide has a Tg sufficiently low to allow extended excursions above the Tg to facilitate reaction without thermal decomposition. Additionally, soluble polyimides can be readily prepared by this approach. Ultimately, high Tg, insoluble polyimides are still only accessable via traditional soluble precursor routes. 

This route was described more or less simultaneously by Karasz et al. 235) and by Murase et al.236). The precursor polymer is typically prepared by reaction of the appropriate bis(chloromethyl)arylene compound with dimethylsulfide in a polar solvent237,238). The product is a water-soluble polymer which can be cast to give thin films. Elimination of hydrochloric acid and dimethyl sulfide takes place on heating the film in the range 200 to 300 °C and can be monitored by thermogravimetry and by the development of colour and conductivity 239. Poly(p-phenylene vinylene), prepared by the precursor route, can be doped to much higher conductivities than the conventionally synthesised polymer. 

In the soluble precursor route, a suitable precursor is synthesized which can be cast into a device structure (i.e., film) by using solution processing. Then it can be converted into the final nonlinear structure upon subsequent treatment (such as heat treatment). This approach has been used for poly-p-phenylenevinylene (PPV) as shown below (32) ... 

Conjugated polymers like poly(l,4-phenylene-vinylene), PPV, or more generally Poly(arylene-vinylenes), PAVs have evoked considerable interest as electrically conductive and nonlinear optical materials. More recently, electroluminescence properties of PPV have attracted substantial attention, since it was first reported in 1990. Direct synthesis of PPV has been limited by its insolubility. Hence, the most commonly used routes are based on soluble polymer precursors or soluble conjugated precursors. The latter process is also commonly referred to as the sulfonium-based polyelectrolyte precursor route. PPV thin films from these solution-based routes, however, have problems related to contamination by solvents and oxidative defects in the polymer. C VP is an alternate method for the deposition of high quality thin films of PPV. Reported first by Iwatsuki et al., it was investigated for electroluminescence applications by Staring et al. ... 

Despite their inherent electronic advantages, CT complexes and radical cation salts tend to be brittle and unprocessable. This problem might be overcome by the incorporation of oligomeric tetrathiafulvalenes in polymers, whereby the TTFs can be part of a main-chain or side-chain polymer. The key concern thereby is to achieve the suitable packing of the donor moieties, which is, of course, less perfect than in the crystalline state. Remarkably, the rigid-rod poly-TTF 164 could be made recently by a precursor route in which 164 is made by dimethyl disulfide extrusion of the precursor polymer (scheme 39). The electrical conductivity after iodine doping amounts to 0.6 S/cm [221]. Other examples of TTF-containing polymers, either in the backbone [222] or in the side-chain [223], are summarized in chart 25. 

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... 

Processing through a precursor route involves the use of an intermediate, processible polymer that can be later converted into the fully conjugated material. It is most often used with poly(para-phenylene vinylene (PPV), a relatively stable and insoluble polymer that can be manipulated as soluble precursor polymers to form films and fibers. There are many different... 

Nguyen L. H., Gunes S., Neugebaner H., Sariciftci N. S., Banishoeib F., Henckens A., Cleij T., Lutsen L. and Vanderzande D. (2006), Precursor route poly(thienylene vinylene) for organic solar cells photophysics and photovoltaic performance . Solar Energy Mat. Solar Cells 90, 2815-2828. 

Parent poly(thienylene vinylene) has also been synthesized by an aldol precursor route [122]. In this method, 5-methyl-2-thiophenecarbaldehyde 76 is treated with a base and the monomer polymerizes yielding a precursor 77 which is soluble in water. Thermal treatment in an acidic solution at 80 °C yields the fully conjugated material. Alternatively, the solid polymer may be heated to 280 °C to effect elimination of water. Fully conjugated material exhibits low conductivity (10 S cm ) in its pristine state. 

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],... 

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