Ethylene pressure has been used to control the competition between isomerization (chain walking) and monomer insertion processes for ethylene coordination polymerization catalyzed by a palladium-alpha-diimine catalyst. The topology of the polyethylene varies from linear with moderate branching to "hyperbranched" structures. Although the overall branching number and the distribution of short-chain branching change very slightly, the architecture or topology of the polyethylene changes from linear polyethylene with moderate branches at high ethylene pressures to a hyperbranched polyethylene at low pressures.

The availability of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is currently limited because they are produced mainly by marine fisheries that cannot keep pace with the demands of the growing market for these products. A sustainable non-animal source of EPA and DHA is needed. Metabolic engineering of the oleaginous yeast Yarrowia lipolytica resulted in a strain that produced EPA at 15% of dry cell weight. The engineered yeast lipid comprises EPA at 56.6% and saturated fatty acids at less than 5% by weight, which are the highest and the lowest percentages, respectively, among known EPA sources. Inactivation of the peroxisome biogenesis gene PEX10 was crucial in obtaining high EPA yields and may increase the yields of other commercially desirable lipid-related products. This technology platform enables the production of lipids with tailored fatty acid compositions and provides a sustainable source of EPA.

A group of polyethylenes synthesized using palladium R-diimine catalysts were studied using 13 C NMR spectroscopy, intensity light scattering, dynamic light scattering, and viscometry. These catalysts are known to produce branched polyethylenes without R-olefin comonomers. The series of polymers studied were synthesized under conditions of varying ethylene pressure. The polymers are highly branched and completely amorphous and are thus soluble in common organic solvents at ambient temperatures. Light scattering determinations of the root-mean-square radius of gyration (Rg) and the molecular weight M of fractions eluting from a size exclusion chromatograph demonstrated that, at a given M, Rg decreased as ethylene pressure decreased. The hydrodynamic parameterssthe Stokes radius (RH) from dynamic light scattering and the intrinsic viscosity ([η])salso decreased. The change in Rg at a constant M results from the change in branching topology for the polymers synthesized at different ethylene pressures. The parameter Rg 2 /M varies by an order of magnitude for the polymers synthesized under ethylene pressures varying from 0.1 atm to 500 psi. However, the total branching (methyls per 1000 CH2) and the distribution of short branches (methyl, ethyl, propyl, etc.) determined by 13 C NMR remained essentially unchanged. These observations indicate the branching topology changes with polymerization pressure. Polymer topology varies from predominantly linear with many short branches at higher ethylene pressures to a densely branched, arborescent globular structure at very low ethylene pressures. Polymers synthesized at the lowest ethylene pressure studied, 0.1 atm, exhibited dilute solution parameters similar to those observed for dendrimers or many-armed stars, with R g/RH below unity, and a segment density approaching that of a hard sphere.