A new eco-friendly strategy for the preparation of linear and hyperbranched polycarbonates was developed.
Our work referred to a one-pot condensation polymerization of various alcohols (diols and triols) with
equivalent amounts of eco-friendly dimethyl carbonate (DMC) at 120
C, atmospheric pressure and in 1,4-
dioxane solution using 4-dimethylaminopyridine (DMAP) or lithium acetylacetonate (LiAcac) as a catalyst.
Polymer chains were built by pure transesterification of hydroxyl and methyl carbonate chain ends, and the
single byproduct (methanol) was removed using a pressure-equalized addition funnel filled with 4 °A
molecular sieves as the crucial equipment in this work. Using this strategy, hyperbranched polycarbonates
with high molar masses (Mn up to 10 000 g mol1 and Mw up to 64 000 g mol1) and high hydroxyl end
group contents (up to 94%) were successfully prepared using dimethyl carbonate instead of toxic
phosgene or phosgene-based monomers for the first time. In addition, linear aliphatic polycarbonates of
various diols were also synthesized with Mn up to 16 000 g mol1 and low molar mass distributions (ĐM <
1.70). Another eco-friendly aspect of this work was the use of equimolar amounts of DMC to avoid waste
and the disposal of excess DMC; in a classic 2-step polycondensation for polycarbonate synthesis excess
DMC is a prerequisite in order to obtain high molar masses.