Daicel Chemical Industries, Ltd.

Masaki Akatsuka

Takuzo Aida

Shohei Inoue

Disclosed are a lactone polymer, a carbonate polymer, a lactone-carbonate random or block copolymer which are mono-dispersed, that is, which have a molecular weight distribution of nearly 1, or, in which purity of a polymer component having a unitary structure is very high, and processes for the preparation thereof which comprise a ring-opening addition reaction of a lactone monomer and/or a cyclic carbonate monomer with a ring-opening initiator in the presence of an organic aluminum-based Lewis acid represented by general formula (I), ##STR1## wherein R is an alkyl group having a carbon number ranging from 1 to 4, Y is independently selected from a substituted group, and p is any one of 1, 2 and 3.

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Kashiwa, Japan

Masaki Akatsuka