The Discovery of PA

In 1958, Natta tried to synthesize PA by bubbling acetylene gas through a titanium/trialkyl aluminum catalyst solution while stirring. One of the products in the reaction was a black, semicrystalline powder that was completely insoluble and unstable in the presence of air and water [4]. Although no analyses could be made, Natta assumed that he had made a high-molecular-weight, mostly trans, PA. Subsequently, PA was observed as a side product in the attempts to cyclotrimerize and cyclotetramerize acetylene [5]. 

Because of PA s extended ir-system, its chains are rigid rods and are therefore insoluble in organic solvents and intractable. PA is also highly air-sensitive. While exposure to oxygen will initially dope the chain, giving a rise in conductivity (vide infra), oxidation is facile and causes the formation of carbonyls and hydroxyls in the PA backbone. PA degrades by simple aging as well, probably because of the presenee of residual catalyst or other impurities. The IT bonds in the PA backbone are also very susceptible to 

---