Amorphous Ibuprofen Confined in Nanostructured Silica Materials: A Dynamical Approach

The molecular mobility of condensed matter confined to nanometer dimensions can be dramatically changed from those of the bulk state in such a way that, when the guest is a drug, it can be advantageously used in pharmaceutical applications. We show by dielectric relaxation spectroscopy that the molecular mobility of the important ibuprofen drug embedded in nanoporous SBA-15 is significantly influenced by the confinement. An evidence of the existence of two families of molecules with different molecular mobilities is provided and investigated in their temperature dependence. One family is due to molecules close to the pores' center with a higher mobility compared with the bulk at low temperatures, and another family with slower dynamics originated from molecules interacting with the pore walls. The work reports the simultaneous manifestation of true confinement and surface effects in this nanostructured silica host for a drug. For future applications in drug delivery systems, the dynamics determined by the guest-host interplay and the one of the bulklike molecules can be tuned to achieve a desired release profile.