Temperature directed-assembly of coated-laponite nanoparticles in pluronic micellar solutions

Abstract

We investigate the microstructure of copolymer micellar solutions with embedded laponite colloidal particles. The solutions exhibit microscopic confinement of the coated nanoparticles triggered by increasing the temperature above the gelation temperature. The copolymer is pluronic which self-assembles into well-defined nanostructured arrays. These self-assembly properties are governed by copolymer–solvent interaction through temperature. In the presence of laponite nanoparticles, a large amount of copolymer unimers adsorb onto laponite. Above the gelation temperature of the pure copolymer micelles in solution, the study demonstrates that the remaining micelles form three-dimensional polycrystallites and trigger the confinement of the nanoparticles in the interstices between them. This conclusion is supported by phase contrast optical and fluorescence microscopy techniques which show the appearance of well-contrasted grains that form when the temperature increases, with excluded fluorescent nanoparticles from the grains. Finally, the contrast matching small-angle neutron scattering displays the development of an interparticle correlation peak revealing their strong confinement in the sample.