Syntheses of Polyesters from Succinic Anhydride and Various Diols Catalyzed by Metal Triflates

Succinic anhydride (SuAh) was polymerized with various α,ω-alkanediols from 1,3-propanediol up to 1,10-decanediol. Most polycondensations were conducted in bulk at temperatures of 80 °C with bismuth triflate as catalyst and number average molecular weights (M n s, uncorrected SEC data) up to 35 000 Da were obtained. Polycondensations of SuAh with 1,6-hexanediol were also catalyzed with aluminum, tin(II), scandium, lanthanium, samarium, and hafnium triflate. Whereas, poor results were achieved with La-triflate, aluminum and tin(II) triflate yielded M n s comparable to those obtained with Bi-triflate. With exception of the basic lanthanum triflate, all other catalysts generated small amounts of ether groups. The MALDI-TOF mass spectra proved that the molecular weights depended on the conversion and on the extent of cyclization. The polycondensations of 1,4-butanediol at temperatures up to 120°C were affected by the formation of tetrahydrofuran, and even with an excess of the diol M n s <10000 Da were not obtained. Yet, BiCl 3 and Bi-triflate catalyzed polycondensations in refluxing decalin gave satisfactory results (M n s ≈ 30 000 Da, uncorrected SEC data).