Biodegradable/radiopaque polymers are highly beneficial for drug delivery systems especially in controlling drug release and monitoring the drug diffusion paths. In the previous research, iodine compounds were bonded with the side chains of linear polyesters through functional groups to synthesize biodegradable/radiopaque polymers. The synthesized iodinated polyesters, however, were mechanically weak and fragile and it has been ardently desired to improve the physical properties of such iodinated polyesters.<br/>Poly(glycerol adipate) (PGA) with hydroxyl groups on their side chains, can be synthesized through enzyme-catalyzed polymerization of glycerol and divinyl adipate. It should be noted that a small amount of secondary hydroxyl groups in glycerol took part in the transesterification, resulting in the branching of the polymer chains from 5-30 mol%, which decreased the hydroxyl group contents of the polyester.<br/>In this study, radiopaque PGA was synthesized via enzymatic polymerization and subsequent condensation with iodine compounds (Fig). Iodoacetic acid (IA), 2-iodobenzoic acid (IBA), and 2,3,5-triiodobenzoic acid (TIBA) were used as iodine compounds, and benzoic acid (BA) was chosen as a control compound. The synthesized polymers were named PGA-I, PGA-IB, PGA-3IB, and PGA-B, respectively. Some iodinated polymers were in an elastomeric state. In fact, the branching of PGA may have worked as effective crosslinking, leading to the rubbery state of the polymers. From <sup>1</sup>H NMR analysis, it was confirmed that all hydroxyl groups in PGA were used for iodination. Moreover, the radiopacity of synthesized polymers was compared by CT scan.

Branched aliphatic polyester with biodegradability and radiopacity via enzymatic polymerization and condensation with iodine compounds

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