A novel pyrolysis-hydrogenation-GCMS technique has been developed and applied to branched polyethylenes of both the high-pressure and low-pressure varieties. The unique features of the technique are pyrolysis at low temperatures (360 °C) and low extent of pyrolysis of the sample (approximately 2% volatilized). This yields a high percentage of pyrolysis products pertaining to the branch points. Study of model ethylene-a-olefin copolymers shows that the pyrolysis products from branch points can be predicted solely by consideration of the possible carbon-carbon scissions a and ß to the branch points. The variety of products from high-pressure polyethylene, however, is greater than that expected simply from the branch-formation mechanism proposed by Roedel and Willbourn. An expanded polymerization scheme has been formulated that includes the occurrence of intramolecular 1,3 hydrogen transfers as well as intramolecular 1,5 hydrogen transfers in the formation of short-chain branches.
A novel method for studying stoichiometry and equilibrium pressures of solid complexes is described. Based on an introduction of a nonvolatile inert solvent which forms a stable suspension with the solid phases, the method has been applied to the SrCl2-NH3 system in the temperature range 283-306 K. The investigation has shown that the decomposition of the octammine of SrCl2 yields diammine (and not monoammine) and that the equilibrium pressure of NH3 for the process can be described by the following equation: In P/torr = -4988/ T + 22.81.
This manuscript describes a laboratory
experiment that provides
students with an opportunity to create conductive silver nanogrids
using polymeric templates. A microcontact-printed polyvinylpyrrolidone
grid directs the citrate-induced reduction of silver ions for the
fabrication of silver nanogrids on glass substrates. In addition to
template-directed nanofabrication, students gain experience using
a sputter coater, a scanning electron microscope, and an atomic force
microscope. Students are also introduced to elemental analysis using
energy dispersive X-ray spectroscopy. Institutions with limited characterization
capabilities can use a compound light microscope to view the structures
reported in this manuscript.
Eine neue Methode zur Untersuchung der Stöchiometrie und der Gleichgewichtsdrücke fester Komplexe, die auf stabiler Suspendierung der festen Phase in einem nichtflüchtigen inerten Lösungsmittel basiert, wird auf das System SrCl2‐NH3 in Heptanol‐(1) im Temp.‐Bereich 283‐306 Kangewendet.
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