title: Thermogelling aqueous fluids containing low concentrations of Pluronic F127 and laponite nanoparticles.
abstract: The triblock copolymer Pluronic F127 (PF127) is frequently used in colloidal and pharmaceutical formulations. Concentrated aqueous solutions of PF127 (>15 wt %) are known to undergo thermogelling (i.e., a sol-to-gel transition upon heating), which is attributed to the formation of a volume-filling cubic array of micelles. Here, we report that thermogelling can occur at much lower PF127 concentrations (1.2 to 8 wt %) if nanoparticles of laponite (25-nm-diameter disks) are also present in the formulation. Thermogelling in laponite/PF127 mixtures requires each component to be present above a minimum level. The gels have moduli around 100 Pa, and they can be reversibly liquefied to sols upon cooling. Rheological techniques, small-angle neutron scattering (SANS), and transmission electron microscopy (TEM) are used to characterize the thermogels. We attribute the onset of thermogelling to depletion flocculation of the laponite particles into a network by spherical micelles of PF127.
authors.affiliation: Department of Chemical & Biomolecular Engineering, University of Maryland, College Park, Maryland 20742-2111, USA.
authors.forename: Kunshan
authors.initials: K
authors.lastname: Sun
authors.forename: Srinivasa R
authors.initials: SR
authors.lastname: Raghavan