Making poly(alkylene carbonates) of controlled molecular weight

摘要

Poly(alkylene carbonates) of controlled molecular weight are made by copolymerizing carbon dioxide and one or more oxirane compounds using zinc polycarboxylate catalyst in the presence of a sterically hindered organic proton donor. The acidity of the donor is in the range of 3 to 20 pKa and the steric quality of the donor is such that it has a steric parameter (Es) of -0.38 or less. The molecular weight of the polymer can be regulated by altering the level of proton donor over a range which does not adversely affect catalyst productivity. Benzoic acid and phenol are examples of suitable proton donors. The preferred catalyst is one made from zinc oxide and a dicarboxylic acid, such as glutaric acid or adipic acid.