He attended Point Loma Nazarene University in San Diego, CA, where he worked with Professor Victor L. Heasley on the halogenation of unsaturated carbonyl compounds. After receiving his B.A. degree in Chemistry in 1997, he began his graduate career at the University of Illinois with Professor Jeffrey S. Moore. Currently he is in his fifth year investigating solvent effects on the helix−coil transition in oligo(m-phenylene ethynylene) foldamers. Matthew J. Mio (left) was born in Michigan in 1974. He attended the University of Detroit Mercy, where he worked with Professor Kevin. D. Belfield (now at the University of Central Florida) on the synthesis of nonlinear optical chromophores for use in polymeric systems. He graduated with his B.S. degree in Chemistry in 1997. Later that year, he began his graduate career at the University of Illinois at Urbana−Champaign with Professor Jeffrey S. Moore. There, Matt studied the synthesis and solution/ solid-state properties of oligo(m-phenylene ethynylene) foldamers and graduated with his Ph.D. degree in 2001. He then went to the Chemistry Department at Macalester College (St. Paul, MN) as a Mellon Postdoctoral Fellow to study the synthesis of novel CpCo−cyclobutadienyl-bridged cyclophanes with Professor Ronald G. Brisbois. Thomas S. Hughes (right) is currently a postdoctoral fellow in the research group of Professor Jeff Moore at the University of Illinois. He was born in 1970 in Philadelphia, PA, and received his B.S. degree from Temple University in 1991. In 1999 he received his Ph.D. degree from Cornell University, where he worked in the laboratories of Professor Barry Carpenter. He is currently studying the association kinetics of the binding of a helical oligomer to a rodlike guest. He is also investigating the thermodynamics of oligo(phenylene ethynylene) folding using molecular mechanics. Jeffrey S. Moore (second from right) was born in Illinois in 1962. After receiving his B.S. degree in Chemistry from the University of Illinois in 1984, he completed his Ph.D. degree in Materials Science and Engineering, also at the University of Illinois, with Samuel Stupp (1989). He then went to the California Institute of Technology as an NSF postdoctoral fellow to study with Robert Grubbs. In 1990 he joined the chemistry faculty at the University of Michigan in Ann Arbor. He returned to the University of Illinois in 1993, where he is currently a Professor of Chemistry and Materials Science and Engineering. In 1995 he became a part-time faculty member of the Beckman Institute for Advanced Science and Technology, where he now serves as co-chairman of the Molecular and Electronic Nanostructures Main Research Theme. Ryan B. Prince was born in Robbinsdale, MN, in 1972. He graduated from Southeast Missouri State University in 1995 with his B.S. degree in Chemistry, where he worked for Professor Jin K. Gong on the synthesis and characterization of transition-metal complexes that bind and activate carbon dioxide. He then went to the University of Illinois and worked with Professor Jeffrey...

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The problems of determining reliable, well‐characterized values of kinetic parameters in free‐radical polymerizations are discussed. The origins of the fact that experimental determinations of rate coefficients of ostensibly identical systems often result in quite different values being reported can be ascribed to subtle mechanistic assumptions made in data interpretation, which are considered in detail. A series of recommendations to assist in overcoming these problems, and to highlight their origins, are presented, with emphasis placed on new techniques including those employing laser photolysis and EPR.

The LCST transitions of novel N-isopropylacrylamide (NIPAM) star polymers, prepared using the four-armed RAFT agent pentaerythritoltetrakis(3-(S-benzyltrithiocarbonyl)propionate) (PTBTP) and their hydrolyzed linear arms were studied using 1 H NMR, PFG-NMR, and DLS. The aim was to determine the effect of polymer architecture and the presence of end groups derived from RAFT agents on the LCST. The LCST transitions of star PNIPAM were significantly depressed by the presence of the hydrophobic star core and possibly the benzyl end groups. The effect was molecular weight dependent and diminished once the number of repeating units per arm g70. The linear PNIPAM exhibited an LCST of 35 °C, regardless of molecular weight; the presence of both hydrophilic and hydrophobic end groups after hydrolysis from the star core was suggested to cancel effects on the LCST. A significant decrease in R H was observed below the LCST for star and linear PNIPAM and was attributed to the formation of n-clusters. Application of a scaling law to the linear PNIPAM data indicated the cluster size n ) 6. Tethering to the hydrophobic star core appeared to inhibit n-cluster formation in the lowest molecular weight stars; this may be due to enhanced stretching of the polymer chains, or the presence of larger numbers of n-clusters at temperatures below those measured.

A new concept for the synthesis of hyperbranched macromolecules involving the use of AB x macromonomers containing linear oligomeric units is introduced. This methodology is used for the preparation of a series of novel hyperbranched poly(ethylene glycol) derivatives containing linear poly(ethylene glycol) units of varying lengths and 3,5-dioxybenzoate branching units. An interesting feature of the hyperbranched poly(ethylene glycol) derivatives is their lack of crystallinity, which is used in the design of a new class of polyelectrolyte materials. The dependence of the ionic conductivity on temperature and the concentration of added lithium cations for these novel hyperbranched macromolecules is reported.

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Semiconductor nanowires (NWs) often exhibit efficient, broadband light absorption despite their relatively small size. This characteristic originates from the subwavelength dimensions and high refractive indices of the NWs, which cause a light-trapping optical antenna effect. As a result, NWs could enable high-efficiency but low-cost solar cells using small volumes of expensive semiconductor material. Nevertheless, the extent to which the antenna effect can be leveraged in devices will largely determine the economic viability of NW-based solar cells. Here, we demonstrate a simple, low-cost, and scalable route to dramatically enhance the optical antenna effect in NW photovoltaic devices by coating the wires with conformal dielectric shells. Scattering and absorption measurements on Si NWs coated with shells of SiN(x) or SiO(x) exhibit a broadband enhancement of light absorption by ∼ 50-200% and light scattering by ∼ 200-1000%. The increased light-matter interaction leads to a ∼ 80% increase in short-circuit current density in Si photovoltaic devices under 1 sun illumination. Optical simulations reproduce the experimental results and indicate the dielectric-shell effect to be a general phenomenon for groups IV, II-VI, and III-V semiconductor NWs in both lateral and vertical orientations, providing a simple route to approximately double the efficiency of NW-based solar cells.

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