Substituent Effect on the Anionic Equilibrium Polymerization of Six-Membered Cyclic Carbonates

Anionic equilibrium polymerization behavior of several six-membered cyclic carbonates was examined. The conversions of the monomers reached a constant below 100%, and the final conversion decreased in the order of 1,3-dioxan-2-one (1) > 5,5-dimethyl-1,3-dioxan-2-one (2) > 5,5-diethyl-1,3-dioxan-2-one (3) ≥ 5-methyl-5-phenyl-1,3-dioxan-2-one (4) > 5-ethyl-5-phenyl-1,3-dioxan-2-one (5). The reactions of 2,2-disubstituted-1,3-propanediols were carried out with phosgene dimer to find that the cyclic carbonate (5) was formed quantitatively in the reaction of 2-ethyl-2-phenyl-1,3-propanediol, while the corresponding polycarbonate was formed in the reaction of 2,2-diethyl-1,3-propanediol in 24% yield besides 3. Thermodynamic parameters were estimated in the anionic ring-opening polymerizations of cyclic carbonates (1−5) by Dainton's equation. The obtained ΔHp value in the ring-opening polymerization of each cyclic carbonate reflected the polymerizability. Molecular orbital calculations of the model compounds of ...