in preparing bioabsorbable polyesters containing glycolic acid unit and / or lactic acid unit by the polymerization of glycolide and / or lactide , compositions comprising polyester - silicone copolymers obtained by conducting polymerization in the presence of silicones and the effect of merely mixing the above bioabsorbable polyesters with certain kind of silicones upon the modification , thereby attaining flexibility in particular , of the bioabsorbable polyesters , are disclosed .