Azulene in Polymers and Their Properties

Azulene, a unique isomer of naphthalene, has received much interest from researchers in different fields due to its unusual chemical structure with a negatively charged 5-membered ring fused with a positively charged 7-membered ring. In particular, incorporation of azulene into polymers has led to many interesting properties. This minireview covers functionalization methods of azulene at its various positions of 5- and 7-membered rings to form azulene derivatives including azulene monomers, and gives an overview of a wide range of azulene-containing polymers including poly(1,3-azulene), azulene-based copolymers with connectivity at 1,3-positions of the 5-membered ring, or 4,7-positions of the 7-membered ring, as well as copolymers with azulene units as side chains. Their chemical and physical properties together with applications of azulene-containing polymers have also been summarized.