SUBSTITUENT EFFECT ON THE ANIONIC EQUILIBRIUM POLYMERIZATION OF 6-MEMBERED CYCLIC CARBONATES

Anionic equilibrium polymerization behavior of several six-membered cy clic 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-die thyl-1,3-dioxan- 2-one (3) greater than or equal to 5-methyl-5-phenyl- 1,3-dioxan-2-one (4) > 5-ethyl-5-phenyl-1,3-dioxan-2-one (5). The reac tions of 2,2-disubstituted-1,3-propanediols were carried out with phos gene dimer to find that the cyclic carbonate (5) was formed quantitati vely in the reaction of 2-ethyl-2-phenyl-1,3-propanediol, while the co rresponding polycarbonate was formed in the reaction of 2,2-diethyl-1, 3-propanediol in 24% yield besides 3. Thermodynamic parameters were es timated in the anionic ring-opening polymerizations of cyclic carbonat es (1-5) by Dainton's equation. The obtained Delta H-p value in the ri ng-opening polymerization of each cyclic carbonate reflected the polym erizability. Molecular orbital calculations of the model compounds of the polymers were carried out to fmd that the polymerizabilities of th e cyclic carbonates correlated with the stabilities of the correspondi ng polymer structures. The concentrations of the monomers formed in th e depolymerizations well agreed with the equilibrium monomer concentra tions in the anionic ring-opening polymerizations.