Poly(vinyl alcohol) (PVA) scaffolds are prepared by a cryogenic process that consists of the unidirectional freezing of a PVA solution. The scaffolds exhibit a microchanneled structure, the morphology of which (in terms of pore diameter, surface area, and thickness of matter accumulated between adjacent microchannels) can be finely tailored by the averaged molecular weight of PVA, the PVA concentration in the solution, and the freezing rate of the PVA solution. The resulting PVA scaffolds are suitable substrates for drug‐delivery purposes, the drug release being controlled (from tens of minutes up to several days) by the morphology of the microchanneled structure. In vitro experiments reveal the efficiency of PVA scaffolds for controlling the release of ciprofloxacin into a bacteria culture medium.

Uniform microcrystalline nickel(II) hydroxide particles have been prepared via the homogeneous alkalinization of nickel(II) nitrate solutions by urea hydrolysis. The nature of the precipitated solids depends on the temperature of synthesis. At ca. 423 K, i.e., under the hydrothermal conditions attained by microwave heating, β-Ni(OH) 2 forms upon the fast ripening of R-Ni(OH) 2 . In the range 363-343 K, R-Ni(OH) 2 is always the final product. The evolution of the systems during the precipitation of R-Ni(OH) 2 is analyzed in terms of the kinetic factors that control nucleation and growth. A precipitation mechanism, based on the principle of minimal structural change, is proposed; it is suggested that the edge-on condensation of Ni 4 (OH) 4 4+ tetramers is a key step in the sequence of events that conduct from hexaaquo Ni 2+ to R-Ni(OH) 2 .

No abstract