Poly displacement reaction

Halogen Displacement. Poly(phenylene oxide)s can also be prepared from 4-halo-2,6-disubstituted phenols by displacement of the halogen to form the ether linkage (48). A trace of an oxidizing agent or free radical initiates the displacement reaction. With 4-bromo-2,6-dimethylphenol, the reaction can be represented as in equation 10 ... 

The advantage of the activated displacement polymerization is the facile incorporation of different and unconventional structural units in the polymer backbone. Most of the heteroarylene activated polyethers prepared by this route are soluble in many organic solvents. The solubility behavior of new polyethers is shown in Table 8. In contrast to many polyphenylenequi-noxalines, poly(aryl ether phenylquinoxalines) prepared by the quionoxaline activated displacement reaction are soluble in NMP. Solubility in NMP is important since it is frequently used for polymer processing in the microelectronics industry [27]. 

Ladenheim and Morawetz [23] also showed that the reactivity of the carboxylate units in partially ionized poly(methacrylic acid) (PMA) toward BrCH2COO in the bromine displacement reaction was greatly diminished, while the reaction proceeded at an appreciable rate with uncharged p-bromoacetamide [23]. This inhibition of the reaction of the polyanion with a small anionic reagent can be attributed to the electrostatic repulsion between the polymer and the reagent. 

Three approaches have been tested, as already described above for inorganic supports. The first attempts concern the direct reaction of transition metal carbonyls with unmodified organic polymers like poly-2-vinyl-pyridine.61 62 However, this kind of anchoring is restricted to only a few complexes. Various polymers have been functionalized with donor groups 63-72 ligand displacement reactions using these afforded the corresponding immobilized complexes. Finally, tests with modified complexes and unmodified polymers are scarce because of the low stability of these complexes under the conditions of reactions. 

Brunelle, in Chapter 5, has provided a solution to the problem of quaternary ammonium catalysts being unstable at elevated temperatures in the presence of highly nucleophilic anions. He found that catalysts based on p-dialkylaminopyridinium salts are approximately one hundred times more stable than simple tetraalkylammonium salts and are useful even up to temperatures of 180 C. Especially valuable is the fact that under these conditions a variety of nucleophilic displacement reactions on aryl halides occurs, making possible the economical commercial synthesis of otherwise difficulty available poly aryl ethers and sulfides. 

Production of pol3rmers through poly-substitution or poly-condensation reactions would be expected to be a natural extension of simple PTC chemistry. To a large extent this is true, but as Percec has shown. Chapter 9, the ability to use two-phase systems for these reactions has enormously extended the chemist s ability to control the structure of the polymers produced. Kellman and co-workers (Chapter 11) have also extensively studied poly-substitution displacements on perfluorobenzene substrate to produce unique polymers. 

The resulting catalyst was highly active for cyanide and acetate ion displacements on 1-bromobutane. As expected, soluble low molecular weight quaternary ammonium salts and a soluble quaternized linear poly(ethyleneimine) were even more active, presumably because they had no mass transfer and intraparticle diffusional limitations. These catalysts had a much higher density of charged sites (at least within the micro domains of the poly(ethyleneimine)) than any of the other active quaternary ammonium ion catalysts reported for nucleophilic displacement reactions. 

Displacement reactions are rarely used for the preparation of amines as poly-alkylation reduces yields and makes product mixtures more complex. However, reaction of primary amines with primary and secondary sulfonates can provide good yields of monoalkylated product if care is taken to control the conditions and mode of addition. Benzylamine is particularly common as a primary amine nucleophile since the benzyl group can be removed by hydrogenolysis to give a primary amine. 

Nucleophilic Displacement Reactions of Poly-O-acetylglycosyl Halides.. 39... 

By choosing suitable forcing-conditions, it is possible to induce poly-0-acetylglycosyl halides to undergo bimolecular displacement-reactions. For example. Chapman and Laird studied the reactions of such halides with piperidine in acetone. The second-order law was obeyed, but the reactions were complicated by a concurrent, bimolecular (E-2), elimination reaction. (See Fig. 5 for changes with the D-glucosyl halides.) A selection of the re-... 

Amino, alkoxy, and aryloxy polyphosphazenes are typically prepared by nucleophilic displacement reactions of poly(dihalophosphazenes). Analogous reactions with organometallic reagents, however, result in chain degradation and cross linking rather than in linear, alkyl, or aryl substituted poly(phosphazenes). The thermolysis of appropriate silicon-nitrogen-phosphorus compounds can be used to prepare fully P—C bonded poly(organophosphazenes). The synthesis of two of these materials and their Si—N—P precursors is described here. 

Poly(acrylamidoxime) has been tested on laboratory scale as well as in test plants in the sea in form of cross-linked, macroporous resin granules called Duolite ES 346 153). We succeeded in loading this resin in natural sea water with more than 3600 ppm of uranium corresponding to the uranium content of uranium ores mined today. As in the case of hydrous titanium oxide, poly(acrylamidoxime) most probably accumulates the cation UO + without carbonate ligands via the displacement reaction ... 

An alternative route to the formation of poly(imide)s is the nitro-displace-ment reaction to form the Ultem series of polymers, first exploited by White et al. [11] at General Electric. These, and similar materials, have application in composite materials and as specialty thermoplastics. Compared to the amic acid route described above, the nitro-displacement reaction is highly controlled, and materials of high chemical regularity produced, as demonstrated by White et al. [11] in their solution-state NMR study of Ultem poly(imide)s. 

The halogen end group can be transformed into other functionalities by means of standard organic procedures, such as a nucleophilic displacement reaction. Different authors have investigated this process of the nucleophilic displacement reactions with model compounds, to confirm the feasibility and selectivity. Compounds such as 1-phenylethyl halide, methyl 2-bromopropionate, and ethyl 2-bromoisobutane mimic the end groups of PSs, poly(alkyl acrylates), and poly(alkyl methacrylates), respectively. Different compounds have been tested, such as sodium azide, n-butylamine, and n-butylphosphine. 

Tundo, P., and M. Badiali, High Activity in Displacement Reactions Catalyzed by Quaternary Onium Salts Immobilized on Inorganic Matrices, /feacrive Poly, 10,55(1989). 

Scheme 2.2 Synthesis of poly(arylene ether)s by perfluoro-activated fluoro displacement reaction. Taken from Ref. [42].

Kim et al. prepared poly(biphenylene oxide)s (PBPOl and PBP02) containing -CF3 groups from AB-type monomers [45] through nucleophilic nitro displacement reaction and investigated their properties. To investigate the feasibility of the polymerization, the model reaction was performed with... 

Scheme 2.17 Synthesis of hb poly(arylene ether)s from monomers containing nitro group (a) via selective and sequential S vjAr (preferential fluorine displacement followed by nitro displacement) reaction of As-and BC-type monomers (b) via nitro displacement reaction of A2C-type monomer. Taken from Ref. [76],...

Scheme 2.20 Synthesis of soluble hyperbranched poly(aryl ether)s using fr/s(4-fluoro-3-trifluoromethylphenyl) benzene (63) and three different bisphenols (A2) by -CFa-activated fluoro-displacement reaction. Taken from Ref. [81].

S.K. Park, S.Y. Kim, Synthesis of poly(arylene ether ketone)s containing trifluoromethyl groups via nitro displacement reaction. Macromolecules 31 (10)(1998) 3385-3387. 

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