Effect of the structure of dimethyl 1,4-naphthalenediacrylate on the mechanism of its solid-phase photocyclopolymerization

To examine the effect of molecular structure on the process of photocycload dition, dimethyl 1,4-naphthalenediacrylate (DMNDA) was synthesized and stud ied. The structure of DMNDA molecules and their packing in the DMNDA crysta l were determined. It was demonstrated that the DMNDA molecule has an asymm etrical nonplanar structure: the planes of the substituents are turned with respect to the plane of the naphthalene nucleus. The factors responsible f or this structure of the molecule were considered. The packing of the molec ules in the perfect DMNDA crystal lattice is highly unfavorable for reactio ns of photocycloaddition; such reactions are absent in the DMNDA monocrysta l but occur in polycrystalline samples with the formation of the correspond ing polymer molecules. The mechanism of polymerization was established as c onsisting of the photocyclodimerization of DMNDA and the growth of the poly mer chains due to the photoaddition of dimers. It was assumed that these re actions occur in the range of dislocations at the boundaries of the grains of the polycrystalline system.