Suzuki polymerization

Dow Chemicals group and coworkers [276,350] synthesized similar triarylamine-fluorene copolymers 251 and 252, possessing carboxylic acid substituents, via hydrolysis of the corresponding ethyl ester polymers, prepared by Suzuki polymerization. Due to the very polar substituents, the copolymers 251 and 252 are only soluble in polar solvents such as DMF but not in aromatic hydrocarbons as toluene or xylene, which allowed simple fabrication of multilayer PLEDs by solution processes (Chart 2.65). 

The modified Suzuki polymerization catalyst, dichlorobis(tri-o-tolylphosphine) palladium(II), was also used to prepare poly(2,7-(9,9-di-w-octylfluoiene)-3,6-benzothiadiazole), (I). 

Further use of the Suzuki polymerization has yielded polymeric precursors to planar PPP derivatives 27 [105, 106] (Tour 93 and Lamba). The strategy, shown above in Scheme 32, utilized a postpolymerization cyclocondensation reaction to afford imine-bridged aryl units. Optical absorption data showed that the planarized polymers exhibited large bathochromic shifts relative to the un-cyclized parent polymers. 

Suzuki polymerization of 9,9-di-n-octylfluorene-2,7-di(ethyleneborate) diester, (1), with a biphenyl, (II), or triphenylamine derivative, (III), was used by... 

The Suzuki polymerization is the AA-BB type, and the monomers are usually diarylbromide compounds and diarylboronate esters. It is possible to use diboronic acids as monomers, but the diboronate esters are generally used because they are more easily purified than diboronic acids. 

This monomer, also named 9,9-dihexylfluorene-2,7-diboronic acid bis(l,3-propanediol) ester, is commercially available. The propanediol or pinacol boronate esters of dialkylfluorenes with different alkyl chain lengths are also commercially available products, and these compounds can be used directly in the following Suzuki polymerization. However, the given synthetic procedures for boronate ester monomers will be useful for preparing new fluorene monomers, which are not commercially available. 

Three principal types of Suzuki polymerizations for polyfluorenes have been developed for homopolymers and copolymers by Dow, Cambridge Display Technology (CDT), and Covion, which was merged with Merck. Early detailed experimental procedures were reported in the patent literature (Scheme 5.5 and Table 5.2). These and other groups have used these polymerizations for numerous poly fluorene derivatives (Table 5.3). 

We will start this chapter with a brief review of the origin of the donor-acceptor concept, followed by a short summary of the key chemistries that are used for the synthesis of D-A copolymers e.g., Suzuki coupling and Stille coupling), with a focus on their application towards the polymer synthesis. The classical step-growth polymerization will be next discussed within the context of Pd-catalyzed polycondensation. Then we will briefly discuss two recent, interesting advances in the synthesis of D-A copolymers Pd-free polycondensation and chain-growth Suzuki polymerization. Since the synthesis of D-A... 

Factors to Consider from the Perspective of Suzuki Polymerization... 

The Suzuki reaction shares many common similarities and features with aforementioned Stille reaction, such as similar catalytic cycles and Pd-based catalysts, and wide tolerance of functionalities. Highlighted below are a few notable factors one needs to consider when choosing Suzuki polymerization to prepare D A polymers. Interested readers are referred to a more general review for details on Suzuki polycondensation." ... 

Scheme 15.2 Chain-growth Suzuki polymerization of PFDTBT in ref. 58.

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