Cyclic and Noncyclic Polycarbonates of Isosorbide (1,4:3,6-Dianhydro-<scp>d</scp>-glucitol)

Abstract

Three different synthetic methods were studied with respect to their usefulness for the preparation of poly(isosorbide carbonate) (PIC). Thermal polycondensations of isosorbide with dimethyl- or diethyl carbonate in bulk proved unsuccessful, regardless of the transesterification catalyst. Polycondensations of isosorbide with diphosgene in pyridine gave polycarbonates, the molecular weights of which depended largely on the excess of diphosgene. In all experiments, OH-terminated linear chains were the main products. Similar results were obtained from pyridine-promoted phosgenations in dioxane. However, polycondensations of equimolar mixtures of isosorbide and isomannide mainly yielded cyclic polymers. Pyridine-promoted polycondensations of isosorbide with isosorbide bischloroformate only gave low molar mass polycarbonates. At low temperatures, even-numbered linear chains were the main products, but higher temperatures gave even-numbered cycles. SEC measurements with triple detection evidenced the formation of high molar mass polycarbonates in the phosgenation experiments and a Mark−Houwink equation was elaborated. The glass transition temperatures varied between 115 and 165 °C depending on the molar mass.