Poly containing heterocyclic units, synthesis

Hilborn et al. demonstrated the synthesis of PBOs (Figure 5.29) by polymerization of bis(fluorophenyl benzoxazoles) with bisphenols. This polymerization was based on the activation of the fluoro group toward nucleophilic aromatic substitution by the oxazole component of the benzoxazole heterocyclic [51]. The TgS of the poly(arylene ether benzoxazoles) ranged from 213 to 303 °C, depending on the bisphenol and activated dihalide used in the synthesis. Generally, the TgS increased with the bulkiness of the bisphenol used. The polymers containing the >C(CF3)2 unit in both the benzoxazole and the bisphenol moiety in the monomers showed higher solubility (NMP) compared to the other PBOs. The physical properties of fluorinated poly(arylene ether benzoxazole) s are presented in Table 5.3. 

Hay has reported the synthesis of poly(aryl ether ketones) containing o-dibenzoylbenzene moieties by the polymerization of 1,2-bis(4-fluorobenzoyl) benzene with various bisphenolates in DM AC (32). Transformation of the o-dibenzoyl(benzene) moiety in the polymer chain to a heterocycle by cyclization with small molecules was developed as a means of increasing the pol5mer chain stiffness and solvent resistance. It was demonstrated that reaction of the polymer with hydrazine monohydrate in the presence of a mild acid in chlorobenzene converted the poly(aryl ether ketone) to a poly(aryl ether phthalazine), a new class of heterocyclic-containing polyether (Scheme V) (33). Likewise, reaction of the polymer with benzylamine in a basic medium led to amorphous, thermally stable poly(aryl ether isoquinolines) (Scheme V) (34). Another example of the use of the o-benzoyl cyclization strategy is the intramolecular ring closure of poly(aryl ketones) containing 2,2 -dibenzoylbiphenyl units to form poly(aryl ether phenanthrenes) (35-37). 

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