The mechanism study of cobalt mediated radical polymerization (CMRP) is performed with CoII(TMP), CoII(salen*), and CoII(acac)2 at 60 °C to demonstrate that the control of vinyl acetate radical polymerization is achieved via a degenerative transfer pathway when CoII(TMP) and CoII(salen*) are used but via a reversible termination process with equilibrium constant (Keq) equal to 1.4 × 106 m−1 when CoII(acac)2 is the mediator. Given by the measured Keq in CMRP with varied cobalt complexes and the reduction potential (E1/2) of the corresponding cobalt complexes, a linear correlation between log(Keq), and E1/2 is found and can be used to estimate the Keq of other CMRP systems. With the enriched database of Keq values, the control mechanisms of CMRP are quantitatively defined by CoII/CoIII equilibrium constant. The connection of reduction potential, equilibrium constant, and control mechanism would contribute to the in‐depth understanding of CMRP process.
Triblock copolymer, PEG-b-PDMAEMA-b-PPy, has been shown as an ideal carrier with remarkable siRNA condensation, high stability, efficient gene release, and negligible cytotoxicity for gene delivery.
Cobalt-mediated radical polymerization (CMRP) was used to prepare well-defined poly(vinyl acetate) (PVAc) as the macroinitiator in the reverse atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and styrene (Sty) for the synthesis of block copolymers of PVAc-b-PMMA and PVAc-b-PSty with linearly increased molecular weight and smoothly shifted gel permeation chromatography (GPC) traces. The chain extension from PVAc to PMMA or PSty via the hybridization of CMRP and ATRP required neither a difunctional initiator nor further chain-end modification and was as simple as regular chain extension in the reverse ATRP process. Because the cobalt complex bonded to the chain end of PVAc was dissociated during the ATRP process, this method also efficiently solved the issue of metal removal in the CMRP process.
In
this study, we combined the kinetic measurement and the computational
simulation to build a kinetic model for the hybridization of cobalt-mediated
radical polymerization (CMRP) and atom transfer radical polymerization
(ATRP), which is a novel method for the one-pot synthesis of block
copolymers of less activated monomers and more activated monomers,
such as PVAc-b-PMMA and PVAc-b-PSty.
The rate constants of the two most important reactions for PVAc radical,
the dissociation of PVAc-CoIII(acac)2 and the
deactivation with CuII(PMDETA)Br2, have been
evaluated at 40 °C as 4.99 × 10–3 s–1 and 4.19 × 106 M–1 s–1, respectively. These two kinetic parameters
associated with other rate constants allowed us to build a quantitative
model that can simulate the polymerization behavior observed in the
hybridization of CMRP and ATRP and thus rationalize the mechanism
more precisely.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.