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 ΔH
p value in the ring-opening polymerization of
each cyclic carbonate reflected the polymerizability. Molecular orbital calculations of the model compounds
of the polymers were carried out to find that the polymerizabilities of the cyclic carbonates correlated
with the stabilities of the corresponding polymer structures. The concentrations of the monomers formed
in the depolymerizations well agreed with the equilibrium monomer concentrations in the anionic ring-opening polymerizations.
SUMMARY Synthesis and cationic ring-opening polymerization of a seven-membered cyclic carbonate, 1,3-dioxepan-2-0ne (l), were examined. The cationic ring-opening polymerization of 1 proceeded without decarboxylation at 20 "C to give the corresponding polycarbonate, differently from a six-membered cyclic carbonate (2), for which polymerization is generally accompanied by partial elimination of carbon dioxide. The observed polymerization rate of 1 in nitrobenzene was about 1.3 times faster than that in dichloromethane. The observed pseudo first-order polymerization rate constants of 1 and 2 at 20°C were determined to be 4.15 x lo4 and 4.16 x lod s-', respectively. The observed polymerization rate of 1 was 100 times larger than that of 2. The activation energies in the polymerization of 1 and 2 were estimated to be 6.27 and 8.52 kcal/mol, respectively.
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.