Poly films synthesis, thermal elimination

Synthesis of poly(p-phenylene vinylene) films by thermal elimination on a soluble polyelectrolyte. 

However the material obtained was an unprocessable powder. Unlike substituted polyacetylenes, polyacetylene is insoluble, infusible and unstable in air. The discovery of a technique to synthesize the polymer in the form of a free-standing film and the use of electron donors and acceptors to dope it to have metallic conductivity produced intense interest in the polymer in the last two decades. A wide variety of catalyst systems has been described for the polymerization of acetylene. Besides the route via acetylene polymerization, polyacetylene can also be obtained by a two-step route which involves the synthesis of soluble polymer precursors, which are converted to polyacetylene via thermal elimination and transition-metal-catalysed isomerization, as well as by polymerization of cyclooctatetraene , by dehydrochlorination of poly(vinyl chloride) and by dehydration of poly(vinyl alcohol)... 

Poly(p-phenylene vinylene) (PPV) is a conjugated polymer, which becomes conductive by the addition of electron donors or acceptors [114, 115], Several methods have been reported for the synthesis of PPV [3, 4, 6], Direct chemical polymerization, which was used in the first attempt of synthesizing PPV, gave a product in the form of an insoluble powder that limited the use of the polymer in many applications [116], The most popular method for the preparation of PPV is base-induced polymerization of sul-fonium salt monomer in aqueous solution [114-118], In this method, PPV films are obtained from the precursor polymer after thermal elimination of the sulfonium groups. PPV has also been prepared electrochemically by reducing p-xylene-bis-(triphenylphosphonium). Two approaches are generally used for the synthesis of PPVs the Wessling... 

The preparation of poly(2,5 dimethoxy phenylene vinylene)(DM-PPV) utilized the xanthate precursor route. Many similarities exist between the PPV xanthate thermal elimination and this PPV derivative. Previous studies had attempted to synthesis DM-PPV using the SPR method. The SPR resulted in gel formation during dialysis so that film casting was not possible. The XPR was successful in preparing precursor films that can be thermally converted to DM-PPV. The derivatives of PPV are useful to prepare a polymer with a shift in the absorbance and photoluminescence maximum. DM-PPV exhibits an 100 nm red shift as compared with PPV synthesized via the XPR. 

COT have been described, but an alternative route for synthesis of long conjugated polyenes has been known for many years. A typical example is the base-catalyzed thermal elimination of hydrogen chloride from poly(vinyl chloride). Unfortunately, synthesis of well-characterized polyacetylene by this route was not successful. The first synthesis of high quality, well-characterized polyacetylene films was reported by Edwards and Feast [66]. The process [67-74] consists of three reaction steps as shown in Fig. 7.8. 

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). 

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