Bundle assemblies formation of alternating copolymer: Alternating copolymerization of symmetrical substituted p-quinodimethanes with asymmetrical N,7,7-tricyanoquinone methide imine in solid state

Abstract

Symmetrical 7,7,8,8-tetrakis(alkoxycarbonyl)-p-quinodimethanes with methoxy(1a(Me)) and ethoxy(1b(Et)) as alkoxy groups formed 1:1 charge-transfer complex crystals with an asymmetrical quinoid compound, N,7,7-tricyanoquinone methide imine (2). The 1:1 formation of the crystals was ascertained on the basis of 1H NMR spectroscopy and single crystal X-ray structure analysis. These 1:1 charge-transfer complex crystals (1a(Me)/2 and 1b(Et)/2 monomer cocrystals) underwent photochemical and thermal polymerizations via a radical mechanism with keeping initial crystal shapes in appearance to form stereoregular alternating copolymers in quantitative yields. The stereoregular alternating copolymers formed bundle assemblies in the less order state. The formation of stereoregular alternating copolymers was explained on the basis of the structures of the monomer cocrystals solved by X-ray crystallography. Less-ordered bundle assemblies are considered to be formed by findings that the gravity of each component is not aligned on a straight line within the one-dimensional column with alternating stacked arrangements of 1a(Me) or 1b(Et) and 2 in the crystals, which are caused by asymmetrical 2.