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Updated: Jan 10, 2026

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
Published on: November 21, 2017
Indium alkoxide complexes supported by constrained Schiff-base ligands for the ring-opening (co)polymerization of
Thitirat Piyawongsiri1, Phongnarin Chumsaeng1, Khamphee Phomphrai1
1Department of Materials Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Wangchan, Rayong 21210, Thailand. khamphee.p@vistec.ac.th.
None:
Indium tert-butoxide complexes supported by constrained Schiff-base ligands with different diamine backbones were successfully synthesized (2a-c) and developed for the ring-opening polymerization (ROP) of lactide (LA), glycolide (GA) and ε-caprolactone (CL). Single-crystal X-ray studies reveal that all complexes are monomeric containing a five-coordinate indium metal center. All complexes were highly active for ROP of cyclic esters. The indium tert-butoxide complex having a trans-cyclohexyl backbone (2c) showed very high activities finishing 98% conversion of 200 equiv. of L-lactide (L-LA) in 3 min at room temperature (TOF = 3920 h-1). Polymerization of rac-LA gave stereoblock isotactic-enriched PLA with Pm values of up to 0.85. The kinetic studies of the ROP of cyclic esters revealed a pseudo first-order dependence with respect to monomer concentrations and the rate order of rac-LA ≈ D-LA > L-LA ≫ CL. From the studies of monomer reactivity ratios using complex 2c, the copolymerization of LA with GA gave block copolymers while the copolymerization of LA with CL gave gradient copolymers.
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