Macrocyclic ring-containing polymers synthesis

Synthesis of Macrocyclic Ring-Containing Polymers Via Cyclopolymerization and Cyclocopolymerization... 

The principle of cyclopolymerization has been applied to the synthesis of macrocyclic ether-containing polymers which may simulate the properties of crown ethers. l,2-Bis(ethenyloxy)benzene (a 1,7-diene) and l,2-bis(2-ethenyloxyethoxy)benzene (a 1,13-diene) are typical of the monomers synthesized. Homopolymerization of the 1,7-diene via radical and cationic initiation led to cyclopolymers of different ring sizes homopolymerization of the 1,13-diene led to cyclic polymer only via cationic initiation. Both monomer types were copolymerized with maleic anhydride to yield predominantly alternating copolymers having macro-cyclic ether-containing rings in the polymer backbone. 

An interesting development in monomer synthesis and subsequent polymerization was disclosed earlier this year [51. A synthetic route for preparing giant rings containing about 20 to 40 monomer units was devised. These macrocycles could be polymerized directly to high molecular weight polymers (Equation 3). 

Most of the systems described in Chapter 5 contain small- or medium-sized or multinuclear benzenoid and non-benzenoid arenes. In Chapter 6, Hoger gives an overview over the mastery of the synthesis of macro- and megacycles. He shows different approaches towards shape-persistent macrocycles and carefully examines and discusses selected examples that display the advantages and disadvantages of macrocycle synthesis under kinetic and thermodynamic control. The template approach (both supramolecular and covalent) towards functionalized rings is also discussed and introduces a strong motif of supramolecular chemistry, which is much further developed but in a more polymer-oriented topic, in the next chapter. 

For a synthetic polymer chemist the important question is whether the cyclization processes in cationic ring-opening polymerization can be controlled. If the preparation of linear polymer is attempted, then cyclic oligomers are undesirable side products. This is especially important in synthesis of telechelic polymers containing reactive end groups, because macrocycles would be unreactive admixtures. On the other hand, cyclic polymers, if prepared selectively, could be a valuable materials. 

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