UV-Absorption and Silica/Titania Colloids Using a Core--Shell Approach

Metal-oxo-colloids have been prepared using tetraethoxysilane (TEOS) oligomers with titanium tetra-i-propoxide (TIP) or titanium (di-i-propoxide) bis(acetylacetonate) (TIA) precursors. Transmission electron microscopy (TEM), FTIR, UV-Vis, and photoluminescence spectroscopy were used to investigate the composition, the size, and optical properties of the Si/Ti core–shell colloids. The presence of hetero-bonded silicate structure (Si–O–Ti) was indicated by FTIR spectroscopy. The size of Si/TIP system ranged from 55 to 120 nm and Si/TIA system ranged from 220 to 250 nm. The TEM data indicated that the size of colloids can be controlled by the TIP or TIA content. The Si/Ti system exhibited strong absorption in the UV-range, yet had excellent optical transmittance in the visible range. The Si/Ti systems exhibited a photoluminescence emission at 329 nm

Partitioning of Small Molecules in Hydrogen-Bonding Complex Coacervates of Poly(acrylic acid) and Poly(ethylene glycol) or Pluronic Block Copolymer

Complex coacervation of polymers can be a route to the compartmentalization of aqueous solutions. Presented here is a study of the hydrogen-bonded complex coacervation of poly­(acrylic acid) and poly­(ethylene glycol) or Pluronic block copolymers and the ability of these coacervates to encapsulate various ionic and nonionic dyes as well as a pharmaceutical compound within them. The formation of complex coacervate driven by hydrogen bonding is studied as a function of both pH and salt content with turbidimetry and isothermal calorimetry. Small-angle X-ray scattering shows the presence of micelles within Pluronic containing coacervate materials formed with a Pluronic block copolymer concentration higher than its critical micelle concentration. Although dyes generally partition to the coacervate phase, in the absence of salt, dyes that are able to hydrogen bond with the coacervate components are better incorporated into the coacervate. It is observed that the addition of salt to the polymer solutions increases the hydrophobicity of the environment within the coacervate, increasing the ability to sequester dye molecules for which there is no hydrogen bonding with the coacervate components. These materials are characterized with UV–vis spectroscopy, dynamic light scattering, zeta potential measurements, isothermal calorimetry, small-angle X-ray scattering, and fluorescence spectroscopy