Main-chain heterocyclic polymers, poly

Besides in the liquid phase, some polyreactions are also performed in the solid state, for example, the polymerization of acrylamide or trioxane (see Example 3-24). The so-called post condensation, for example, in the case of polyesters (see Example 4-3), also proceeds in the solid phase. Finally, ring closure reactions on polymers with reactive heterocyclic rings in the main chain (e.g., poly-imides, see Example 4-20) are also performed in the solid state. 

The tetrahydrofuran heterocycle has been incorporated into the main chain of a polymer by a ring expansion reaction of an epoxidized poly(diene) (172) (79BRP1550017). The reaction apparently takes place with equal efficiency (Scheme 85) with either nucleophilic or electrophilic initiation. 

Conjugated polymers incorporated with different heterocyclic moieties were reported. Examples of these conjugated main chains are poly(phenylene vinylene) (10)60 and polybenzoxazole/polybenzthiazole (ll)64 (Scheme 7). In... 

Ladder polymers have their backbone made from an interrupted series of condensed rings. In such polymers, very frequently the rings contain heteroatoms, and the polymer can be considered as part of the class of polymers with heterocycles in the main chain. One of the first synthesized polymers from this class was obtained from the oxidation and heating of polyacrylonitrile [1, 2]. Multifunctional condensations also can lead to ladder polymers. For example, a poly(phenoxazine) is formed from the reaction of a substituted quinone and a diaminodihydroxybenzene as shown below ... 

The stability limit of poly(benzimidazole) is about 25 °C higher than that of polyimide. Through an appropriate choice of reaction partner, many different polymers containing rings in the main chain can be produced. All these products are stable up to about 500 C regardless of the structures of the heterocyclic rings. As a rule, the more thermally stable the polymers are, the less stable they are to hydrolysis. 

For reaction conditions, see the particular references. Fraction of cis double bonds in the polymer main chain Tacticity bias of the cis- or /ra 5-centred dyads Depends on the particular A-substituents of the A-heterocyclic carbene ligands(s), see Ref. [295] Data given for the initially yielded poly(a n-7-methylbornene) Syn-iosmer is polymerized slowly after complete consumption of anti isomer, thus forming a block copolymer Depends on monomer-initiator ratio. 

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