Porphyrin-layered double hydroxide/polymer composites as novel ecological photoactive surfaces

Abstract

Nanocontainer and nanofiller aspects of layered double hydroxides (LDH) were combined to prepare porphyrin-LDH/polymer composites for photoactive coatings. The suggested properties are derived from cytotoxicity of singlet oxygen, O2(1Δg), produced by interaction of molecular oxygen with excited porphyrin molecules located within the interlayer space of ZnRAl and MgRAl LDH. Porphyrins, Pd(II)-5,10,15,20-tetrakis(4-carboxyphenyl) porphyrin (PdTPPC) and 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) photoproducing O2(1Δg), were successfully intercalated into LDH hosts using the co-precipitation procedure and then used as fillers in two eco-friendly polymers, namely polyurethane (PU) and poly(butylene succinate) (PBS). Porphyrin-LDH/polymer composites were prepared either by the solvent cast/cross-linking technique or melt-compounding with different porphyrin-LDH filler loadings (up to 1.3 wt%). Both X-ray diffraction and transmission electron microscopy measurements indicate a good dispersion of porphyrin-LDH fillers into the polymer matrices and that the porphyrin molecules remain intercalated within LDH layers. The polymers do not block the diffusion of oxygen and the triplet states of the intercalated porphyrins in the composite films have enough long lifetimes to produce O2(1Δg) upon irradiation by visible light. The present composites allow the elaboration of photoactive surfaces with a precise control of the O2(1Δg) concentration depending on porphyrin-LDH filler loadings.