Synthesis of Polyarylates

Aryl-aryl cross-coupling reactions have been exploited extensively, particularly by Snieckus and coworkers, in the synthesis of polyaryls and other aromatic nuclei243. 

In an extensive series of papers beginning in 1985, Hart and co-workers [32] developed and elaborated a one-pot reaction for the synthesis of polyaryl benzenes, using aryl Grignard... 

An additional important application of the Kharasch reaction is in the synthesis of polyaryls. For example, 2,5-dibromopyridine (140) was transmetallated upon treatment with isopropylmagnesium bromide to give the corresponding Grignard reagent 141, which subsequently underwent the Kharasch reaction affording the polypyridine (PPy) in 76% yield [43], respectively. Scheme 11. 

Polyarylate oximates (PAO) were prepared from various diketoximes (DKO) and dichloride anhydrides of wo-phthalic (CAIP) and terephthalic acids (CAT). Synthesis of polyarylate oximates was earned out by low temperature eatalytic-acceptor polyeondensation, with triethylamine as catalyst (Fig.l)... 

The full-scale test were performed to find the influence of reaction time, solvent nature, temperature, and reagents feed ration on intrinsic viscosity of polyarylate oximates to find out the optimal reaction conditions for their preparation in accordance with the Scheme 1. It was found that synthesis of polyarylate oximates can be carried out more efficiently in dioxane at 303 K during 40 min. with triethylamine as catalyst and molar ratio DKO/ (CAT) / (DCAIP) = 2/1/1. The reduced specific viscosity r red for a resulting polyarylate oximate was within the range of 0.71-0.81 dl/g. It should be noted that synthesis of polyarylate oximates from phenyl ketoximes in acetone as a solvent proceeded as a heterogeneous proeess and the resulting polymer precipitated from a solution. 

Several polyarylates are liquid cr stalline materials and are widely used as industrial plastics. The synthesis of polyarylates from industrially used diphenols and various diacids has been investigated by Moore and Stupp (Moore, 1990) who published a procedure based on a carbodiimide-mediated esterification in the presence of dimetliylaminopyridinium p-toluene sulfonate (DPTS). 

Side Reactions The major side reaction in the synthesis of polyaryl ethers is due to incomplete dehydration of the polymerization system. 

A novel coupling cyclization reaction of 1,3-diketones with imines was applied for the synthesis of polyaryl substituted 3-trifluoromethylpyrroles. The reaction was promoted by a low-valent titanium reagent and afforded the pyrroles 295 in high to quantitative yields. A number of 1,3-diketones 293 and imines 294 provided a variety of pyrroles 295, bearing different combinations of electron-donating, as well as electron-withdrawing substituents in aromatic rings [100]. 

Recently, they also developed another one-pot synthesis of polyarylated oxazoles from benzylamine and benzU derivatives via oxidative dehydrogenation domino process using air as oxidant (Scheme 8.70). The reaction condition is mild and moderate to good yields could be obtained at room temperature. The C(sp )-H... 

Scheme 8.70 Synthesis of polyarylated oxazoles from benzylamine and benzil derivatives.

Solvent for Displacement Reactions. As the most polar of the common aprotic solvents, DMSO is a favored solvent for displacement reactions because of its high dielectric constant and because anions are less solvated in it (87). Rates for these reactions are sometimes a thousand times faster in DMSO than in alcohols. Suitable nucleophiles include acetyUde ion, alkoxide ion, hydroxide ion, azide ion, carbanions, carboxylate ions, cyanide ion, hahde ions, mercaptide ions, phenoxide ions, nitrite ions, and thiocyanate ions (31). Rates of displacement by amides or amines are also greater in DMSO than in alcohol or aqueous solutions. Dimethyl sulfoxide is used as the reaction solvent in the manufacture of high performance, polyaryl ether polymers by reaction of bis(4,4 -chlorophenyl) sulfone with the disodium salts of dihydroxyphenols, eg, bisphenol A or 4,4 -sulfonylbisphenol (88). These and related reactions are made more economical by efficient recycling of DMSO (89). Nucleophilic displacement of activated aromatic nitro groups with aryloxy anion in DMSO is a versatile and useful reaction for the synthesis of aromatic ethers and polyethers (90). 

Bisphenol-A benzoxazine reaction, under acidic conditions, 416-417 Bisphenol-A polyarylates, 77 synthesis of, 109-113 Bisphenol-A polysulfone, 327 nucleophilic synthesis of, 337 Bisphenolic monomer, 354 Biurets, 227... 

In their efforts to construct stimuli-responsive, supramolecular amphiphiles, Frechet et al. [126-129] reported the synthesis of a novel series of AB and ABA block copolymers via the Williamson ether synthesis (e.g., 47, Fig. 21). Polyethylene glycols (PEGs) of different lengths were used as the linear hydrophilic B block while polyaryl ether dendrons of different sizes were used as the hydro-phobic A block. These copolymers were characterized by optical microscopy,... 

Early and prescient work to develop correlations between biological observables and the physico-chemical properties of polymers were reported by Brocchini and Kohn [3, 32, 166]. Prior to the development of the models, the authors had been engaged in the combinatorial synthesis of a 112-member library of polyarylates, prepared through the condensation of diphenols with diacids (Fig. 12). 

Dendritic analogues of engineering plastics-A general one-step synthesis of dendritic polyaryl ethers [T. M. Miller, T. X. Neenan, E. W. Kwock, S. M. Stein, Macromol. Symp. 1994, 77, 35-49]. 

Coordination carbonylation polycondensation has been extended from the synthesis of polyamides [scheme (15)] and polyarylates [scheme (16)] to reactions using other nucleophilic monomers that, with dihaloarenes and carbon monoxide, yield poly(imide-amide)s, poly(acylhydrazide)s, and poly(benzoxa-zole)s [165,170,171],... 

Stepwise double coupling of two different arylboronic acids with a dihaloarene afforded one-pot, two-step method for synthesizing unsymmetrical teraryls, quateraryls, and other higher order polyaryls.882 The first total synthesis of dragmacidin D involved a sequential double coupling of two different pinacol 3-indoleboronic esters (ArBpin Equation (207)).882... 

The synthesis of teraryls, quateraryls, and further higher-order polyaryls, and the ever-increasing complexity in the more functionalized materials requires simple and practical methods for synthesizing building blocks (Scheme 33). The transmetalation between an aryllithium, -magnesium, or other metal (Al, Si,Zn)... 

For phosphorescence, lanthanide metal ions can be used in a similar manner. Lanthanide ions have very interesting photophysical properties, but often exhibit weak absorption bands, and aggregate to form clusters, which limit their applications. Thus, a dendrimer that can provide a protective shell to isolate a cation and at the same time enhance the emission by transfer from the periphery to the lanthanide ion at the core could be of great interest. Self-assembled lanthanide-cored dendrimers have been prepared to prove such an assumption synthesis was carried out by mixing three equivalents of polyaryl ether dendrons bearing carboxylic acid entity at the focal point with Ln(III) cations [Er(III), Tb(III), and Eu(III)] (Fig. 5.4) [34]. The authors demonstrated that the enhancement of the lanthanide cation emission associated with the dendritic core shell was observed, and an antenna effect from the periphery to the core was shown to promote this process. 

Chapters 7-9 form the second part and describe the hypercrosshnked polystyrene networks. These chapters cover in detail the basic principles of the formation of hypercrosshnked polymers, the synthesis of hypercrosshnked networks and also the properties and morphology of the polystyrene networks. Characterization techniques such as electron microscopy and X ray scattering are also covered. Hypercrosshnked polymers like polysuhbne, polyarylates or polyanilines among others are also reported on as a novel class of polymeric materials. 

The change of the fractal dimension D with temperature reflects the corresponding changes in sizes, degree of compactness and asymmetiy of shape of a macromolecular coil in solution [89]. The importance of the temperature dependence of study is determined by strong influence of this parameter on the processes of synthesis [28], catalysis [90], flocculation [91], so forth. At present as far as we know experimental evaluations of the temperature dependence of a macromolecular coil are absent. Theoretical estimations [13] suppose that the temperature enhancement makes the fractal less compact, that is, leads to Devalue reduction. Therefore, the authors [92] performed the experimental study of dependence on temperature for the macromolecular coils of polyarylate F-1 [5] in diluted solutions and evaluation of change influence on s nithesis processes. 

The indicated aspect of polymers synthesis in different solvents has an important applied significance. As it is known through Ref [5], mechanical properties of polyarylates of comparable molecular weight, but received by methods of equilibrium and nonequilibrium polyeondensa-tion, differ strongly, in addition the first from the indicated methods gives a better complex of mechanical properties. 

Synthesis of biaryls via Pd- or Ni-catalyzed aryl-aryl coupling has found many attractive apphcations in the synthesis of ofigo- and polyaryls and natural products containing biaryls. The former topic is discussed in Sect. IH.2.17.2, and the latter is further supplemented in Table 1 of Sect. IH.2.18. 

Molecular composites in terms of synthesis The reinforcements are also formed by the in-situ reaction in the matrix polymers. Such methods are another way to pursue the limit of molecular dispersion of reinforcing materials. One example is found in the in-situ precipitation of reinforcing silica in polydimethyl siloxane networks with the sol-gel methods [21], Another example is the direct polycondensation of p-aminobenzoic acid or p-hydroxybenzoic acid from their monomers in solutions of polyarylate [22]. Mechanical properties of the cast films indicated increase in modulus and tensile strength at elevated temperatures. 

Figure 2 Synthesis of tyrosine-derived polyarylates. DIPC, 1,3-diisopropylcarbodiimide DMAP, dimethylaminopyridine PTSA, p-toluenesulfonic acid.

---