3,4-Dihydroxyphenyl-L-alanine (DOPA) is an unusual amino acid found in mussel adhesive proteins (MAPs) that is believed to lend adhesive characteristics to these proteins. In this paper, we describe a route for the conjugation of DOPA moieties to poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers. Hydroxyl end groups of PEO-PPO-PEO block copolymers were activated by N,N′-disuccinimidyl carbonate and then reacted with DOPA or its methyl ester with high coupling efficiencies from both aqueous and organic solvents. DOPA-modified PEO-PPO-PEO block copolymers were freely soluble in cold water, and dye partitioning and differential scanning calorimetry analysis of these solutions revealed that the copolymers aggregated into micelles at a characteristic temperature that was dependent on block copolymer composition and concentration in solution. Oscillatory rheometry demonstrated that above a block copolymer concentration of approximately 20 wt %, solutions of DOPAmodified PEO-PPO-PEO block copolymers exhibited sol-gel transitions upon heating. The gelation temperature could be tailored between ∼23 and 46°C by changing the composition, concentration, and molecular weight of the block copolymer. Rheological measurement of the bioadhesive interaction between DOPA-modified Pluronic and bovine submaxillary mucin indicated that DOPA-modified Pluronic was significantly more bioadhesive than unmodified Pluronic.

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Molten salts have traditionally been used as recrystallizing solvents for the crystal growth of mixed metal oxides. In recent years, many examples of the direct preparation of mixed metal oxides from molten salt solutions have been reported. We have been exploring the use of chloride melts as a reaction media to prepare complex early transition metal oxides. Specific examples of new synthetic routes to interesting titanates and niobates will be presented. In one case, we have prepared a series of layered niobate perovskite solid acids from molten salts at temperatures well below those traditionally used in solid state syntheses. In the second case, we have discovered a new synthetic route to a poorly characterized reduced calcium titanate that is otherwise very difficult to make. The synthesis and characterization of these two classes of compounds will be described.