Double-Stranded Polymers
Preparations of many double-stranded polymers were reported. For instance, polypyrrolones were formed from 2,3,5,6-tetraaminobenzene and various dianhydrides or tetracarboxylic acid compounds [213]. Following are two examples:
Different ladder polyquinoxalines were prepared as well. One example is shown below [233]:
Some ladder polyquinoxalines were found to be stable in air at 460C and in nitrogen up to 683C. Not all attempts at formations of ladder polymers yielded completely cyclized fused ring structures. For instance, an attempt to form a polymer from tetraaminonaphthalene with naphthalene tetracarboxylic acid dianhydride failed to yield complete cyclizations [222]. An interesting polymer containing macrocyclic rings was formed from pyromellitic tetranitrile by condensation with dianilino ether [223]:
The description of all the double-stranded polymers that were synthesized and reported in the literature is beyond the scope of this book. This section is concluded by mentioning two more materials. One prepared by an alkali catalyzed polymerization of phenyltrichlorosilane [224]:
The above polymer is cis-syndiotactic [225] with a cis-anti-cis arrangement of the phenyl groups. It is stable at temperatures up to 525C. The other ones are a soluble ladder conjugated polymer, composed of perylene diimides and thieno [3,2 b] thiophene was prepared recently by a synthesis via photo cyclization by irradiation with sunlight [224]. These soluble polymers, prepared for photonic applications, can be illustrated as follows:
