Lamellar self-assembly of a porphyrin derivative possessing poly(ethylene oxide) methyl ether and the formation of a silica-porphyrin hybrid with tetraethoxysilane

A porphyrin derivative, possessing poly(ethylene oxide) methyl ether on the para positions of phenyl groups in the tetraphenylporphyrin, is self-assembled to form a thin film with a lamellar structure. A split of the absorption band in the visible light region of the film strongly indicates the stacking of the porphyrin rings in the film. A molecular periodicity perpendicular to the substrate, proven by in-plane XRD, suggests the perpendicular orientation of the porphyrin rings. A silica-porphyrin hybrid film with a mesostructure was prepared from the mixture of the derivative and tetraethoxysilane. The mesoscale periodicity of the hybrid was confirmed by low-angle XRD and TEM data. The presence of the grafted groups suppressed the segregation of tetraphenylporphyrin rings in the formation of the hybrids, which is in clear contrast to the separated precipitation of tetraphenylporphyrin from a mixture of underivatized tetraphenylporphyrin and hydrolyzed tetraethoxysilane. These results indicate that porphyrin derivatives can be utilized as the organic components in silica-organic hybrids if they are appropriately derivatized.