Spectroscopic properties of zinc porphyrin-functionalized poly(4-vinylporphine) derivatives in the solutions, solid powders and doped PMMA films

Polymeric zinc porphyrin derivatives were prepared through an axial coordination reaction of a charged water-soluble zinc porphyrin (ZnTMPyP) with poly(4-vinylpyridine) (PVP). Molar ratios of the porphyrin substituents relative to the pyridine monomers of PVP in the as-prepared polymeric porphyrins were about 1:30, 1:250 and 1:1000. Moreover, ZnTMPyP and ZnTMPyP-PVP doped poly(methylmethacrylate) (PMMA) composites and their optically transparent thin films were prepared. Compositions and spectroscopic properties of these porphyrins were investigated by using UV-vis absorption, infrared, X-ray electron and fluorescence spectroscopy as well as time-resolved fluorescence spectroscopy. The Soret absorption band of the porphyrins appeared at 438 nm in the methanol solutions, which red shifted to 456 nm in the doped PMMA films. Although the ZnTMPyP solid powders gave off very weak luminescent emission, its functionalized polymers and doped PMMA thin films gave off strong emissions at around 640 nm. It was revealed that emission lifetime of the zinc porphyrin was about 0.2 ns in the solid powders and 0.6-1.5 ns in the polymeric porphyrins and the doped composite thin films.