Polymer with heteroaryl backbones

Polymers with heteroaryl backbones could also be prepared by this method (178,180). 2,5-Dichlorothiophene was polymerized by this method (equation 52) (178). High molecular weights were not obtained due to premature precipitation of the polymer. The transarylation side reaction (equation 9) was inhibited by the presence of bipyridine and excess PPhs (vs. NiCh). 

Polyamides are polymers with carboxamides groups (-NR-CO-, with R = H, alkyl, aryl or heteroaryl) in the backbone chain. Homopolymers of polyamide-type can be divided into two groups polyamides of AA/BB-type and polyamides of AB-type. The different polyamides are characterized by the number of C-atoms in the monomer unit. 

A 2,2 -bithiophene-based monomer has more than one type of reactive C-H bond, although reactions typically occur in the 5- and 5 -positions first. Attempts to copolymerize 2,2-bithiophene with dibromo compound rendered materials with low solubility due to cross-linking in the 3,3 - and 4,4 -positions of the bithiophene monomer. To evade these side reactions, the other reactive C-H bonds on the thiophene monomers were blocked with methyl groups. P37 and Pjg were synthesized by direct heteroarylation polymerization. However, the film absorption onsets were hypsochromically shifted compared to the unprotected bithiophene analogs. The methyl groups indeed cause twisting in the polymer backbone and disrupt conjugation. 

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