Enhancement of Emission by Surfactant-Induced Aggregation in Poly(phenylenevinylene)-Based Lipochromophores

A study has been carried out on the surfactochromicity of four new highly lipophilic poly(phenylenevinylene) (PPV) chromophores. Micellar encapsulation by a detergent such as cetyltrimethylammonium bromide (CTAB) imparts solubility to these compounds in aqueous solution. Before the critical micelle concentration (CMC) was reached the emission intensity of the chromophores increased significantly with the concentration of CTAB. After reaching the CMC, the quantum yield tended to stabilize. Concentrations of PPV up to 100 mu M could be encapsulated without any evidence of saturation or modification of the CMC value of the surfactant. Transmission electron microscopy (TEM) experiments demonstrated that aggregation of the molecules occurred and this led to a highly efficient Forster resonance energy transfer (FRET) when different chromophores were encapsulated within the micelle. This situation was not observed in organic solutions at similar concentrations in the absence of CTAB. The detergent shielding also prevented protonation of amine derivatives 3 and 4 in acidic media. These mixed surfactant/fluomphore systems not only maintained but also improved the already good emission properties of PPVs 1-4 in the solid state. This behavior makes these systems suitable for applications such as 3D printing due to their compatibility with alcoholic and/or aqueous solvents.