Four-center type photopolymerization in the crystalline state. V. X-ray crystallographic study of the polymerization of 2,5-distyrylpyrazine

Changes in crystal structure during polymerization and oligomerization of 2,5-distyrylpyrazine have been investigated by x-ray crystallography. The polymer and the oligomer as obtained are three-dimensionally oriented, and the directions of the three axes of the resultant crystals coincide with those of the original crystal. The space group of the products also agrees with that of the monomer. It is concluded that the polymer and the oligomer crystals approximately duplicate the molecular arrangement in the monomer crystal. The polymerization mechanism is discussed on the basis of the crystal structures.