Ullmann polymerization

A larger blue shift in fluorescence was observed for alkoxycarbonyl-substituted PTs 400 and 401. The polymers were prepared from 2,5-dibromo-substituted monomers by two methods (i) Ullmann reaction with Cu powder and (ii) Ni(0)-mediated polymerization (Scheme 2.63) [485]. Both polymers have similar molecular weights (Mn 3000), although the Cu-prepared polymers showed higher quality and lower polydispersity. PL emission maxima for the Cu-prepared polymers 400 and 401 were red-shifted, compared to the Ni-prepared polymers (by 13-15 nm ( 0.05 0.06 eV) in solution and 25-30 nm ( 0.08 O.lOcV) in films, Table 2.4). This demonstrates that the properties of the polymer depend on the preparation method and, consequently conclusions from small shifts of 0.05-0.1 eV in PL EL energies of the materials, prepared by different methods, should be made with care. 

The syntheses of 1 utilized the Ullmann ether synthesis.13 Reaction of 2 mol of 1-bromonaphthalene with 4,4-(hexafluoroisopropylidiene)diphenol afforded the desired product 1. The reaction was carried out in DM Ac at 160°C in the presence of potassium carbonate as the base and copper (I) iodine as the reaction catalyst to yield 1, as depicted in Scheme 1. The reaction proceeded slowly but in good yield with easy isolation of the desired compound. Acylation of 1 with 4-fluorobenzoyl chloride to prepare 2 was carried out under modified Friedel-Crafts reaction conditions14 using dimethyl-sulfone as catalyst moderator. Both 1 and 2 were easily recrystallized to yield high-purity monomers suitable for polymerizations. 

Mehnert, R. in Radiation chemistry radiation induced polymerization, in Ullmann s Encyclopedia of Industrial Chemistry, Vol. A22, VCH Weinheim, p. 471 (1993). Garratt, P.G., Strahlenhartung, Curt R. Vincentz Verlag, Hannover, p. 61 (1996). In German. 

The remaining polymerization route involves zero-valent nickel complexes and dihalide monomers. Variations of this route most often arise where different sources or regeneration methods of the active nickel species are utilized [82,199, 200-204]. A typical example is shown below in Scheme 51 in which poly(3-phe-nylthiophene) 50 is synthesized from the parent 2,5-dichlorothiophene. As with the Ullmann reaction, polymerization appears to be most compatible with ring systems containing electron-withdrawing substituents. 

Government Rubber Styrene. General-purpose synthetic rubbers that were originally produced in government owned plants as GR-S. They are copolymers obtained by the polymerization of butadiene and styrene in a ratio of approx 3 1. The chains contain a random sequence of the two monomers. Very similar in composition to Buna S, bra ton, Sol-p re pie, Stereon. Review P. Schneider el at., in Ullmann,... 

Hamielec AE, Tobita H. Polymerization processes, 1. fundamentals. In Ullmann s Encyclopedia of Industrial Chemistry. WUey-VCH Verlag GmbH Co. KGaA 2000. 

Table 19.1 Properties of poly(3-R-thiophene)s, prepared by the Ullmann, Yamamoto or FeCI polymerizations... 

The carbonate salt produced becomes a brownish color due to the formation of polymerization products of HCN (Ullmann s, 1987). 

Attempts have been made to prepare PPP and oligo-phenylenes via the Ullmann reaction and the Wurtz-Fittig reaction.For example, treatment of / -dibromobenzene with Na gives an oligo-/ -phenylene, as shown in Scheme 4.1. This oligo-/ -phenylene is thought to have a degree of polymerization (DP) of 8 based on analytical data. ... 

J. Duffy and J. E. Puskas, Synthesis of Butyl Rubber by Cationic Polymerization, in Ullmann s Encyclopedia of Industrial Chemistry, Vol. A23, 6th ed., Wiley-VCH, Weinheim, 1998, p. 51. 

The Ullmann reaction was found suitable for the polymerization of substituted phenylenes such as methyl-[39], nitro-[40] and perfluorophenylene [41]. For instance, 3,3 -dinitro-4,4 -diodobiphenyl treated under Ullmann conditions [40] produced a bright yellow polymer (Scheme 6.11) with an average degree of polymerization of 52 as determined by iodine analyses. Nitro substituents along the polymer backbone increased the solubility in polar solvents, such as... 

A copolymer of aniline and thiophene was obtained by the Ullmann condensation polymerization of dibromothiophenes and / -phenylenediamines at 185°C [153]. The polymer, consisting of alternative thiophene and aniline units, showed an excellent thermal stability up to 400° C. This alternating structure is confirmed by the infrared spectra, which resemble a superposition of the spectra of polyaniline and polythiophene and molecular-weight determinations. Unfortunately, no conductivity data have been supplied. 

Method of synthesis - three methods are used for synthesis, including oxidative coupling, radical polymerization, and Ullmann reaction Hnk, J K, High Peformance Polymers, William Andrew, 2008. 

The Ullmann reaction (Fig. 7) was also attempted for the synthesis of poly(p-phenylene), but onfy low-molecular-weight products with structural irregularities were obtained. The Ullmann reaction, however, was found suitable for the polymerization of substituted phenylenes such as methyl-, nitro-, and perfluoropheny-lene [244-247]. 

Control over 2,5-linked polypyrrole is achieved by means of Stille chemistry. f-BOC-protected pyrroles are converted into bromo-trimethyl stannyl monomers and subsequently polymerized using a Pd catalyst. The so-obtained low-molecular-weight material can next be converted to polypyrrole by thermal deprotection [545]. Ullmann coupling has also been used to prepare... 

Ullmann coupling polymerization of 2,5-dibromo-3-alkylthiophene carboxy-lates by Pomerantz is an excellent way to prepare ester derivatives of PTs [175] (Scheme 16). The M,i s of these materials were in the 4K region with PDIs around 2. Subsequent electroluminescent studies and bilayer devices were prepared and... 

The Ullmann reaction (79) and the metal mediated oxidative polymerization (20) were used for the synthesis. These methods are replaced by metal catalyzed reactions nowadays. Schluter and Wegner (27) used in 1989 the coupling of boronic acids described by Susuki (22) to synthesize soluble polyphenylenes. The Pd catalyzed reaction tolerates a large number of functional groups. The diaryl coupling of Kumada can be used as well to synthesize polyphenylenes (29,J0). 

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