A. Initiator efficiency as judged by the 1H NMR yield of polymer. B. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, MALDI-TOF MS, of the product of EDA polymerization initiated with 2. C. Exploration of Mn control based on the [EDA]:[initiator] ratio, error bars equals standard deviations, : GPC-MALLS in tetrahydrofuran, THF, at 35 °C was used to analyze polymer samples. Note: for 1, with [EDA]: = 50 and 100, Mn is overestimated due to exclusion of the portion of the peak that overlapped with low-Mn species/solvent impurity. D. EDA polymerization and dimerization mediated by 2 monitored by 1H NMR spectroscopy, CD2Cl2, 500 MHz, −40 °C).
Carbene polymerization provides polyolefins that cannot be readily prepared from olefin monomers. However, controlled and living carbene polymerization has been a long-standing challenge.
Published in JACS, Aleksandr V. Zhukhovitskiy repors a new class of initiators, (π-allyl)palladium carboxylate dimers, which polymerize ethyl diazoacetate, a carbene precursor in a controlled and quasi-living manner, with nearly quantitative yields, degrees of polymerization >100, molecular weight dispersities 1.2–1.4, and well-defined, diversifiable chain ends.
The metod described method also provides block copolycarbenes that undergo microphase segregation. Experimental and theoretical mechanistic analysis supports a new dinuclear mechanism for this process.