Bull. Hist. Chem., VOLUME 42, Number 1 (2017) 63 CUPRENE: A HISTORICAL CURIOSITY ALONG THE PATH TO POLYACETYLENE Seth C. Rasmussen, Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND,
[email protected] Introduction Although the most structurally simple of the con- jugated polymers, polyacetylene is not nearly as old as The historical importance of polyacetylene was other conjugated materials such as polyaniline or poly- cemented in 1977, when a collaboration between Hideki pyrrole (6-9). In fact, it was not until 1955 that Giulio Shirakawa, Alan G. MacDiarmid, and Alan J. Heeger at Natta (1903-1979) reported the first successful produc- the University of Pennsylvania revealed that it was pos- tion of polyactylene (11, 12). As outlined in Figure 2, sible to achieve metallic conductivity from free-standing Natta’s methods utilized combinations of triethylalumi- films of the conjugated organic polymer when treated num (Et3Al) and titanium(IV) propoxide (Ti(OC3H7)4) with oxidizing agents such as I2 or AsF5 (1-8). Although to catalytically polymerize the gaseous acetylene to a previous studies on oxidized conjugated polymers such black crystalline polymeric product (12). as polypyrrole, polyaniline, and polyacetylene (Figure 1) had revealed conductivities in the semiconducting range (6-9), the ability to generate metallic conductivities from an organic plastic seemed to promise a wealth of possible Figure 2. Natta’s catalytic polymerization of acetylene. new applications and brought unprecedented attention to these conducting organic polymers. In recognition of this, the 2000 Nobel Prize in Chemistry was awarded to Although not prepared directly from acetylene, Shirakawa, MacDiarmid, and Heeger for their pioneering oligomeric analogues known as polyenes (–CH=CH–)n work with polyacetylene and their early contributions to predate Natta’s work, with the phenyl-capped series the field of conjugated organic polymers (10).