Synthesis and agglomeration of gold nanoparticles in reverse micelles

Reverse micelles prepared in the system water, sodium bis-(2-ethylhexyl) sulfoccinate (AOT), and isooctane were investigated as a templating system for the production of gold nanoparticles from Au(III) and the reducing agent sulfite. A core-shell Mie model was used to describe the optical properties of gold nanoparticles in the reverse micelles. Dynamic light scattering of gold colloids in aqueous media and in reverse micelle solution indicated agglomeration of micelles containing particles. This was verified theoretically with an analysis of the total interaction energy between pairs of particles as a function of particle size. The analysis indicated that particles larger than about 8?nm in diameter should reversibly flocculate. Transmission electron microscopy measurements of gold nanoparticles produced in our reverse micelles showed diameters of 8-10?nm. Evidence of cluster formation was also observed. Time-correlated UV-vis absorption measurements showed a red shift for the peak wavelength. This was interpreted as the result of multiple scattering and plasmon interaction between particles due to agglomeration of micelles with particles larger than 8?nm.     

Grafting of methyl methacrylate on EPR and EPDR: Impact properties of polyvinyl chloride grafted polymer blends

EPDM rubber can be brought into water suspension after swelling in n-heptane containing proper emulsifiers and in shear stress; particles reach dimensions as low as 150 Å. Methyl methacrylate in emulsion can be grafted easily with Bz₂O₂ on the rubber. Grafting yields depend particularly on the monomer/rubber ratio. The grafted polymer can be recovered by precipitating the emulsion with acetone, which eliminates the homopolymer. The grafting mechanism is discussed in terms of different initiators (AIBN and Bz₂O₂) and unsaturated (EPDM) and saturated rubber (EPR); AIBN and PMMA radicals were inactive in abstracting hydrogen atoms from rubber chains. Mechanical properties of the blends with PVC of the raw graft product are discussed on the basis of the grafted polymer composition and synthesis conditions. Very high impact strength can be reached at 15% rubber content in the blend for a grafted polymer obtained from a monomer/rubber ratio equal to 0.75.     

Sloan Foundation Scholarship Program: Mentoring Undergraduates toward Doctoral Degrees

In the last decade rapid advances and complex nature of new and improved technologies and fierce competition are demanding a more profound expertise at all professional levels in Chemical Engineering related industries. Graduate programs are an attractive option to fill this need. This and other factors led the chemical engineering department at the University of Puerto Rico Mayagüez campus to implement several programs and initiatives in order to encourage students to pursue doctoral degrees. A key component of this strategy is the Sloan Foundation Undergraduate Scholarship Program. During the first three years a significant increase (from 2 to 10% of the graduating BS class) resulted in those continuing to graduate school. The main components of the program are mentoring, undergraduate research, summer internships, and graduate school orientation seminars.