title: Interaction of FeIII-tetra-(4-sulfonatophenyl)-porphyrin with copolymers and aggregation in complex micelles.
abstract: Aggregation of Fe(III)-tetra-(4-sulfonatophenyl)-porphyrin (Fe(III)TPPS) was studied in the presence of block copolymers, poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP), poly(ethylene glycol)-block-poly(2-(dimethylamino)ethyl methylacrylate) (PEG-b-PDMAEMA), and poly(ethylene glycol)-block-poly(β-cyclodextrin) (PEG-b-PCD). The interaction between the iron porphyrin and the blocks, P4VP, PDMAEMA, and PCD, led to the formation of copolymers/Fe(III)TPPS complex micelles with a PEG shell and determined the species of Fe(III)TPPS. The electrostatic interaction of protonated P4VP and PDMAEMA with Fe(III)TPPS remarkably decreased the apparent pKd of Fe(III)TPPS and led to a micellar μ-oxo dimer of the iron porphyrin. At pH above the pKa of P4VP, Fe(III)TPPS was kept inside the hydrophobic P4VP core and formed an encapsulated μ-oxo dimer. However, when above the pKa of PDMAEMA, Fe(III)TPPS escaped from the hydrophobic PDMAEMA core, existing as a free μ-oxo dimer. PCD caused the monomer of the porphyrin because of the inclusion complexation between the β-cyclodextrin residues and Fe(III)TPPS. The two micellar monomer species Fe(III)TPPS(H2O)2 and Fe(III)TPPS(OH) were obtained with an equilibrium pKa ~ 6.4.
authors.affiliation: State Key Laboratory of Hollow Fiber Membrane Materials and Processes, School of Materials Science and Engineering, Tianjin Polytechnic University, Tianjin 300387, People's Republic of China.
authors.forename: Lizhi
authors.initials: L
authors.lastname: Zhao
authors.forename: Ang
authors.initials: A
authors.lastname: Li
authors.forename: Rui
authors.initials: R
authors.lastname: Xiang
authors.forename: Liangliang
authors.initials: L
authors.lastname: Shen
authors.forename: Linqi
authors.initials: L
authors.lastname: Shi