Abstract
Aggregation of 5,10,15,20-tetrakis-(4-sulfonatophenyl)-porphyrin (TPPS) was investigated in complex micelles composed of poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP) and poly(2-(dimethylamino)ethyl methylacrylate)-b-poly(N-isopropylacrylamide) (PDMAEMA-b-PNIPAM) in aqueous solutions. The resultant complex micelles had a complex P4VP/PDMAEMA/TPPS core and a mixed PEG/PNIPAM shell. Different noncovalent interaction modes between the porphyrin and each copolymer accomplished a co-effect on the aggregation of TPPS. The formation of aggregates was pH-dependent. At pH 3.2–6.5, TPPS existed as a mixture of H-aggregates and monomers because of the aromatic-aromatic interaction with P4VP and electrostatic interaction with PDMAEMA. The monomers translated into J-aggregates, stabilized by electrostatic interaction with the both polyelectrolyte blocks, upon decreasing the pH to 1.6. The free-base monomer was the one and only form for the dye at pH 11.0 due to aromatic stacking with the pyridyl rings.
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