Experimental studies of the jamming behaviour of triblock copolymer solutions and triblock copolymer-anionic surfactant mixtures

Polymer conformation in nanoscopic soft confinement

We study the conformation of a polymer (polyethylene glycol) in a nanoscopic soft confinement with attractive walls. The polymer is added to a water-in-oil microemulsion based on the deuterated anionic surfactant AOT, d-octane and D₂O. Three different droplet sizes and up to three polymers per droplet are investigated with small angle scattering combining X-rays and neutrons. This allows determining the confinement size and polymer conformation on identical samples. Whereas polymer conformation in bulk is found to be well described with the model of a Gaussian coil its radius of gyration is drastically increased in the droplet. At the same time it is compressed on a local scale. This supports the picture of a polymer strongly adsorbed on the surfactant layer with a thickness of several Angstroms.

Encapsulation of hydrophobic drugs in Pluronic F127 micelles: effects of drug hydrophobicity, solution temperature, and pH

Three drugs, ibuprofen, aspirin, and erythromycin, are encapsulated in spherical Pluronic F127 micelles. The shapes and the size distributions of the micelles in dilute, aqueous solutions, with and without drugs, are ascertained using cryo-scanning electron microscopy and dynamic light scattering (DLS) experiments, respectively. Uptake of drugs above a threshold concentration is seen to reduce the critical micellization temperature of the solution. The mean hydrodynamic radii and polydispersities of the micelles are found to increase with decrease in temperature and in the presence of drug molecules. The hydration of the micellar core at lower temperatures is verified using fluorescence measurements. Increasing solution pH leads to the ionization of the drugs incorporated in the micellar cores. This causes rupture of the micelles and release of the drugs into the solution at the highest solution pH value of 11.36 investigated here and is studied using DLS and fluorescence spectrocopy.