Topochemical photopolymerization of muconic derivatives in the crystalline state via a radical chain reaction mechanism

The photoreaction behaviors of various muconic derivatives, dialkyl (Z,Z)-muconates (1), N,N'-dialkyl-(Z,Z)-muconamides (2), and di(alkylammonium) (Z,Z)-muconates (3) in the crystalline state were investigated. The crystals of these compounds provided the corresponding (E,E)-isomers or tritactic polymers as the photoproducts during irradiation using a high-pressure mercury lamp, depending on the structure of alkyl substituents. The isomerization and polymerization were revealed to proceed via a crystal-to-crystal process based on the powder X-ray diffraction. The ammonium derivatives with higher n-alkyl substituents were found to have a high polymerization reactivity to yield a polymer with a meso-diisotactic-trans-2,5-structure and high molecular weight, similar to the polymerization of the previously reported diethyl ester.