Aprotic lithium-oxygen (Li-O 2 ) batteries show great promise in energy storage and transportation applications because of their high gravimetric energies, which potentially represent a several-fold increase over Li-ion batteries. The stable and reversible operation of Li-O 2 batteries, however, is currently hindered by the severe degradation of common electrolytes. Here, we show that sulfonamidebased electrolytes, designed on the basis of physical organic chemistry principles, can exhibit higher (electro)chemical stability than common electrolytes, such as tetraglyme and DMSO.
We
report an improved synthesis of poly(3-hydroxypropionate) (P3HP)
from ethylene oxide (EO) and carbon monoxide (CO) through the intermediate
β-propiolactone (PL). The optimized carbonylation of EO resulted
in high selectivity for PL using a bimetallic [Lewis acid]+[Co(CO)4]− catalyst. Anionic ring-opening
polymerization of PL by organic ionic compounds to afford P3HP was
also investigated. A phosphazenium carboxylate initiator displays
the highest activity for the polymerization and produces polyesters
with molecular weights over 100 kDa and narrow molar mass distributions.
Furthermore, the known rearrangement of PL and the thermolysis of
P3HP provide efficient EO-based routes to the important commodity
chemical acrylic acid.
Nickel α-diimine catalysts have been previously shown to perform the chain straightening polymerization of αolefins to produce materials with melting temperatures (T m ) similar to linear low density polyethylene (T m = 100−113 °C). Branching defects due to mechanistic errors during the polymerization currently hinder access to high density polyethylene (T m = 135 °C) from α-olefins. Understanding the intricacies of nickel α-diimine catalyzed α-olefin polymerization can lead to improved ligand designs that should allow production of chain-straightened polymers. We report a 13 C NMR study of poly(α-olefins) produced from monomers with 13 C-labeled carbonsspecifically 1-decene with a 13 C-label in the 2-position and 1-dodecene with a 13 C-label in the ω-positionusing a series of α-diimine nickel catalysts. Furthermore, we developed a mathematical model capable of quantifying the resulting 13 C NMR data into eight unique insertion pathways: 2,1-or 1,2insertion from the primary chain end position (1°), the penultimate chain end position (2 p °), secondary positions on the polymer backbone (2°), and previously installed methyl groups (1 m °). With this model, we accurately determined overall regiochemistry of insertion and overall preference for primary versus secondary insertion pathways using nickel catalysts under various conditions. Beyond this, our model provides the tools necessary for determining how ligand structure and polymerization conditions affect catalyst behavior for α-olefin polymerizations.
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