The effect of substituents of the anionic polymerization of α-oxides

Polymerization of epoxide monomers promoted by tBuP4 phosphazene base: a comparative study of kinetic behavior

“…The coordination between alkoxide and HtBuP 4 + stabilizes the transition state and initiates the epoxide cleavage. 34 The substituents present on the monomer are known to play an important role in the transition state 35 which is confirmed in our case. The methyl and ethyl groups of PO and BO do not interact with the phosphazenium counter-ion in the transition state (Figure 4).…”

“…A similar effect has already been observed for the sodium phenolate initiated AROP of methyl glycidyl ether and thiomethyl glycidyl ether compared to the one of propylene oxide. 35 More recently Lynd and coll.…”

Ring-opening polymerization of glycidylic compounds: influence of the glycidylic oxygen in the coordinative mechanism

“…For the mechanism described above, the most important coordinative site in the monomer is the oxiranic oxygen, whose relative basicity is affected by the oxirane substituents 21) . It should also be taken into account that there may be a cooperative or competitive effect of other coordinative centers which are present in the neighboring substituents 22,23) .…”

Conventional Oxyanionic versus Monomer-Activated Anionic Copolymerization of Ethylene Oxide with Glycidyl Ethers: Striking Differences in Reactivity Ratios

“…Regarding steric properties, similar reactivity of EEGE and EO seems counterintuitive, since one would expect the ring opening of EEGE to be sterically hindered, in analogy to propylene oxide . However, it is well-known that coordination of the counterion (potassium in this case) to the epoxide ring activates C–O bond cleavage, − which should be facilitated for EEGE due to its additional oxygen atoms. In this context, DFT calculations of analogous glycidyl ethers revealed lower transition state energies for the attachment of the glycidyl ether to the growing chain end due to (i) better complexation of the potassium counterion and (ii) increased Lewis basicity of the epoxide ring compared to EO .…”