Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometalate anions, and radionuclides. Details addressing the design, synthesis, and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental cleanup necessary after 40 years of weapons-grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented.
The aqueous solutions of poly(ethylene glycol) grafted with poly(lactic acid-co-glycolic acid)
flow freely at room temperature but form gels at higher temperature. The existence of micelles in water
at low polymer concentration was confirmed by cryo-transmission electron microscopy and dye solubilization studies. The micellar diameter is about 9 nm, and the critical micelle concentration is in a range
of 0.01−0.05 wt %. The critical gel concentration, above which a gel phase appears, was 16 wt %, and the
sol-to-gel transition temperature was slightly affected by the concentration between 16 and 25 wt %. At
sol-to-gel transition, viscosity and modulus increased abruptly, and 13C NMR showed molecular motion
of hydrophilic poly(ethylene glycol) backbones decreased while that of hydrophobic poly(lactic acid-co-glycolic acid) side chains increased. The hydrogel of PEG-g-PLGA with hydrophilic backbones was
transparent during degradation and remained a gel for 1 week, suggesting a promising material for short-term drug delivery.
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