A novel route for synthesizing esters and polyesters from the Diels–Alder adduct of levopimaric acid and acrylic acid

A novel route for the esterification of the Diels–Alder adduct between abietic acid, in its isomer form of levopimaric acid, and acrylic acid was established. The high purity Diels–Alder adduct was prepared starting from rosin acids. When the adduct was subjected to a condensation reaction in the presence of a cyclic carbonate ester and of an efficient amine catalyst, hydroxyalkyl esters were obtained. The corresponding linear polyesters were synthesized by the advanced polycondensation of the above intermediates at high temperature, under vacuum, and in the presence of some adequate polyesterification catalysts. In the work 1,3-dioxolan-2-one as cyclic carbonate ester, triethylamine as esterification catalyst, and toluene-4-sulfonic acid monohydrate or tetrabutyl titanate as polycondensation catalysts, were preferred for exemplifications. The polyesters were soluble in dimethylacetamide, trichloromethane, tetrahydrofuran, 1,1,2,2-tetrachloroethane, or 1,4-dioxane. The thermal and electric studies showed that the polymers were substances with good thermal stability and high dielectric properties.

The Diels–Alder adduct between levopimaric acid and acrylic acid was reacted with 1,2-dioxolan-3-one, in the presence of a catalyst, to give hydroxyethyl esters. These were used as monomers in polyester synthesis, as shown in figure. The physicochemical characterization of the polyesters showed that these were amorphous and medium-molecular-weight polymers, with high melting temperatures, good thermal stability, and high dielectric properties.Figure optionsDownload as PowerPoint slide