On the Method of Pulse-Heated Analysis of Solid Reactions (PHASR) for Polyolefin Pyrolysis.

The continued need for plastics necessitates an effective solution for processing and recycling polymer wastes. While pyrolysis is a promising technology for polyolefin recycling, an experimental apparatus must be designed to measure the intrinsic kinetics and elucidate the chemistry of the plastics pyrolysis process. To resolve this issue, a modified Pulse-Heated Analysis of Solid Reactions (PHASR) system was designed, constructed, and evaluated for the purposes of polyolefin pyrolysis.

Molecular self-assembly at bare semiconductor surfaces: characterization of a homologous series of n-alkanethiolate monolayers on GaAs(001).

Structural trends for a homologous series of n-alkanethiolate self-assembled monolayers (SAMs), C(n)H(2n+1)S- with 12 < or = n < or = 19, on GaAs(001), studied by a combination of grazing incidence X-ray diffraction and infrared spectroscopy, along with ancillary probes, show an overall decay in organization with decreasing n, with the largest changes occurring below n = 15-16. The long-chain monolayers form a mosaic structure with < or =10 nm domains of molecules organized in an incommensurate pseudo-hcp arrangement with nearest neighbor distances of 4.70 and 5.

Value of zeolites in asymmetric induction during photocyclization of pyridones, cyclohexadienones and naphthalenones.

Two strategies, namely chiral inductor and chiral auxiliary approaches, have been examined within zeolites with the aim of achieving asymmetric induction during the photocyclization of cyclohexadienone, naphthalenone and pyridone derivatives. Within zeolites, enantioselectivity as high as 55% and diastereoselectivity as high as 88% have been obtained. The observed stereoselectivities are significant given the fact that these reactions gave very little stereoselectivities in isotropic solution media.

A simple technique to grow polymer brushes using in situ surface ligation of an organometallic initiator.

A simple approach is described here for the in-place synthesis of polymer brushes by surface-initiated polymerization. A cyano-terminated self-assembled monolayer on a gold surface was used to anchor a highly active cationic Pd organometallic initiator by ligand exchange. We grew ultrasmooth patterned poly(4-methoxystyrene) brushes with excellent thickness control at room temperature.

Molecular self-assembly at bare semiconductor surfaces: preparation and characterization of highly organized octadecanethiolate monolayers on GaAs(001).

Through rigorous control of preparation conditions, organized monolayers with a highly reproducible structure can be formed by solution self-assembly of octadecanethiol on GaAs (001) at ambient temperature. A combination of characterization probes reveal a structure with conformationally ordered alkyl chains tilted on average at 14 +/- 1 degrees from the surface normal with a 43 +/- 5 degrees twist, a highly oleophobic and hydrophobic ambient surface, and direct S-GaAs attachment. Analysis of the tilt angle and film thickness data shows a significant mismatch of the average adsorbate molecule spacings with the spacings of an intrinsic GaAs(001) surface lattice.

The dynamics of noble metal atom penetration through methoxy-terminated alkanethiolate monolayers.

We have studied the interaction of vapor-deposited Al, Cu, Ag, and Au atoms on a methoxy-terminated self-assembled monolayer (SAM) of HS(CH(2))(16)OCH(3) on polycrystalline Au[111]. Time-of-flight secondary ion mass spectrometry, infrared reflection spectroscopy, and X-ray photoelectron spectroscopy measurements at increasing coverages of metal show that for Cu and Ag deposition at all coverages the metal atoms continuously partition into competitive pathways: penetration through the SAM to the S/substrate interface and solvation-like interaction with the -OCH(3) terminal groups. Deposited Au atoms, however, undergo only continuous penetration, even at high coverages, leaving the SAM "floating" on the Au surface.

Asymmetric photoreactions within zeolites: role of confinement and alkali metal ions.

In this Account strategies using zeolites as media to achieve chiral induction are presented. Diastereomeric excesses as high as 90% and enantiomeric excesses up to 78% have been obtained with selected systems within zeolites. The same systems show no asymmetric induction in solution.

Zeolite-coated quartz fibers as media for photochemical and photophysical studies.

Zeolite-coated optical fibers are useful as media to carry out asymmetric photochemical reactions and for sensing polyaromatic compounds.

Enhanced enantio- and diastereoselectivities via confinement: photorearrangement of 2,4-cyclohexadienones included in zeolites.

[reaction: see text] Employing zeolite as the reaction medium, it is possible to change the enantio (from achiral dienones) and diastereo (from chiral dienones) selectivities during the oxa-di-pi-methane rearrangement of 2,4-cyclohexadienones.