The ring-opening transesterification polymerization (ROTEP) of rac-lactide (rac-LA) using L(X)Zn catalysts (L(X) = ligand having phenolate, amine, and pyridine donors with variable para substituents X on the bound phenolate donor; X = NO2, Br, t-Bu, OMe) was evaluated through kinetics experiments and density functional theory, with the aim of determining how electronic modulation of the ligand framework influences polymerization rate, selectivity, and control. After determination that zinc-ethyl precatalysts required 24 h of reaction with benzyl alcohol to convert to active alkoxide complexes, the subsequently formed species proved to be active and fairly selective, polymerizing up to 300 equiv of rac-LA in 6-10 min while yielding isotactic (Pm = 0.72-0.78) polylactide (PLA) with low dispersities: Đ = 1.06-1.17. In contrast to previous work with aluminum catalysts for which electronic effects of ligand substituents were significant (Hammett ρ = +1.2-1.4), the L(X)Zn systems exhibited much less of an effect (ρ = +0.3). Density functional calculations revealed details of the initiation and propagation steps, enabling insights into the high isotacticity and the insensitivity of the rate on the identity of X.
This research output has an Altmetric Attention Score of 4. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 11 November 2017.
All research outputs
#8,742,382
of 26,796,023 outputs
Outputs from Inorganic Chemistry
#5,569
of 25,156 outputs
Outputs of similar age
#128,362
of 347,253 outputs
Outputs of similar age from Inorganic Chemistry
#64
of 318 outputs
Altmetric has tracked 26,796,023 research outputs across all sources so far. This one has received more attention than most of these and is in the 67th percentile.
So far Altmetric has tracked 25,156 research outputs from this source. They receive a mean Attention Score of 2.9. This one has done well, scoring higher than 77% of its peers.
Older research outputs will score higher simply because they've had more time to accumulate mentions. To account for age we can compare this Altmetric Attention Score to the 347,253 tracked outputs that were published within six weeks on either side of this one in any source. This one has gotten more attention than average, scoring higher than 62% of its contemporaries.
We're also able to compare this research output to 318 others from the same source and published within six weeks on either side of this one. This one has done well, scoring higher than 78% of its contemporaries.
