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Chiral Micelles of Achiral TPPS and Diblock Copolymer Induced by Amino Acids

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journal contribution
posted on 25.08.2009, 00:00 by Lizhi Zhao, Xin Wang, Yan Li, Rujiang Ma, Yingli An, Linqi Shi
Chiral complex micelles prepared by 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and the poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG114-b-P4VP61) in the presence of aspartic acid (Asp), tryptophan (Trp), and lysine (Lys) were investigated in aqueous solutions at pH 2.0. TPPS formed J-aggregates in the micellar core. The morphology and optical properties of the complex micelles depended on the properties of amino acids and the preservation time for the mixed solutions of TPPS and amino acids before adding the copolymer. Prolonging the preservation time, the spherical morphology of the complex micelles remained unchanged in the presence of the Asp. On the contrary, a morphology evolution from sphere to rod took place for Trp and Lys. The intensity of the circular dichroism (CD) signals of the complex micelles increase with the preservation time, and the chirality sign was determined by amino acids. l-Trp and l-Lys led to a negative chirality sign and l-Asp a positive one while the corresponding enantiomers contributed to the opposite sign. Lower concentration of amino acids could not transfer their chirality to the aggregates of TPPS, and at higher concentrations of TPPS, it took more time for the aggregates to express the chiral information on amino acids.