Ultralong cylindrical micelles precisely located with semiconductor nanorods by solvent evaporation-driven self-assembly.

ABSTRACT

We demonstrate the efficient incorporation of PS-tethered cadmium sulfide nanorods (PS-CdS NRs) into polystyrene-block-poly(ethylene oxide) (PS-b-PEO) ultralong cylindrical micelles by solvent evaporation-driven self-assembly. The hexadecyl trimethyl ammonium bromide (CTAB) was used as the surfactant in chloroform-in-water emulsions. It is a prerequisite to improve the enthalpic compatibility between the CdS NRs and the PS block of PS-b-PEO to accomplish their cooperative assembly. We investigated the effects including the concentration of CTAB in the aqueous solution ([CTAB]), the weight fraction of CdS NRs (f), the volume ratio of the organic solvent to water and the magnetic stirring rate on the cooperative assembly behaviors. The different morphologies of hybrid assemblies formed at varied [CTAB] were rationalized in view of the adsorption of the aqueous surfactant and block copolymer at the oil-water interfaces, thereby leading to the disparate mechanisms by which the organic-water interfacial instabilities proceeded. This work presents an extremely precise location of the CdS NRs in the centers of the cylindrical micelles, i.e. 95.2% of the CdS NRs were distributed in the central ca. 4 vol% regions of the cylinders and all of them were dispersed in the central ca. 38% radial spans. The length of the hybrid cylindrical micelles can reach tens of micrometers. The ultralong cylindrical micelles functionalized by the CdS NRs in the central cores can lower the toxicity of the CdS NRs and improve the biocompatibility, which have potential applications in fluorescence probes, labels and many others.